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Volume 79, 1951
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Studies on the Earthworm Fauna of New Zealand—I

[Read before the Wellington Branch, May 30, 1951; received by the Editor, May 30, 1951]

Introduction

This paper is the first of a series intended to cover the systematics of the New Zealand earthworm fauna, and to give some introduction to the group as a whole.

The New Zealand earthworm fauna may be divided into two groups, the first a large group of species belonging to the family Megascolecidae and making up the endemic fauna, and the second, a small group of species belonging to the family Lumbricidae, which have been introduced from the northern hemisphere, accidentally or deliberately, by the agency of man. It is with the first of the above groups that this series of papers will be mainly concerned.

The family Megascolecidae is divided into seven sub-families, of which only three, the Acanthodrilinae, Megascolecinae and Octochae-tinae are represented in the New Zealand region. Twenty-one genera, containing over eighty species, have been identified from this region by previous workers. The most energetic of the previous workers on the group was Sir William Benham, of Dunedin, who worked over a long period on the endemic fauna. Others who contributed materially to the present knowledge of the group were Beddard and the two German zoologists Michaelsen and Ude. The scheme of classification followed in these papers will be that of Michaelsen (1900) as set out and slightly modified by Stephenson (1930).

Many, if not all, earthworms are specifically identifiable at sight by the experienced student, but the general features of size, colour, habit, etc., which permit the ready identification of species are most difficult of description, and accordingly systematists rely on a mass of minute description from which one or more features are selected as having high generic and specific value. The features selected may vary from genus to genus and the following is an account of the morphological characters which have been found to be reliable systematic characters and of the variation in other characters to which systematic importance has sometimes been attached.

Generic Characters

Genera of the family Megascolecidae are distinguished from one another by the following features:

(1) Number and arrangement of chaetae on each segment. There are two fundamental arrangements:

(a) Lumbricine—as found in Rhododrilus, where there are four pairs of chaetae on each segment, a dorso-lateral and a ventro-lateral

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pair on each side. In describing the arrangement of chaetae, those of each side are designated in order from the ventro-medial to the dorso-medial by the letters a, b, c, d. This is the most frequently occurring chaetal arrangement and from it, in many genera, has been derived the other arrangement.

(b) Perichaetine—as found in Plagiochaeta, where there is a large number of chaetae, or pairs of chaetae evenly spaced around each segment.

The lumbricine arrangement of chaetae is invariable, but in those genera which have the perichaetine arrangement, there may be variations between species in the number of chaetae, or pairs of chaetae, on each segment. In such cases the number of chaetae per segment is often a valuable specific character (as in some species of Pheretima).

(2) Nephridia: The usual condition is the meganephridial condition, in which there is in each segment a pair of elongate coiled nephridial tubules opening to the exterior by a pair of small pores. From the meganephridial condition, in many genera has been evolved the micronephridial condition, as seen in Octochaetus, where there is a large number of small nephridial tubules usually arranged in a band round the lateral aspects of the peritoneum or in paired clusters, one on each side of the ventral nerve cord in each segment. A condition intermediate between the meganephridial and the micronephridial conditions is seen in some genera, e.g. in certain species of Megascolides there are micronephridia in each segment, but in some of the posterior segments meganephridia occur in association with them.

(3) Arrangement of the Nephridiopores: In nearly all the meganephridial genera of the Megascolecidae the nephridiopores are in a single series on each side of the body, but in the three genera comprising the Neodrilacea (a group of genera peculiar to New Zealand) and in some species of Perionyx the nephridiopores alternate more or less regularly between a dorso-lateral and a ventro-lateral position in successive segments.

(4) Male Genital Apparatus: The number and positions of the prostatic pores and of the associated male pores are used to distinguish genera. The more general arrangement is the “acanthodriline,” in which there are two pairs of prostatic pores, a pair on segment xvii and a pair on segment xix, and a single pair of male pores on segment xviii (as in Acanthodrilus). The “acanthodriline” arrangement may be considered as the primitive arrangement and from it the other two arrangements may be derived in the following manner:

(a) The “microscolecine” arrangement in which the posterior pair of prostates and their pores disappear and the male pores may, or may not, unite with the prostatic pores on segment xvii or on segment xviii (e.g. Rhododrilus, Megascolides).

(b) The “balantine” arrangement in which the anterior pair of prostates and their pores disappear, and the male pores unite with the prostatic pores on segment xviii (e.g. the South African genus Udeina).

These arrangements may undergo variations, and the importance attached to such variations is not standardised. Benham (1909) distinguished the genus Leptodrilus for two species which resembled

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the genus Rhododrilus in all other features except that the prostatic pores open on segment xvi instead of on segment xvii or on segment xviii, but Stephenson does not consider a similar modification in some species of Notoscolex to be of sufficient importance to justify the establishment of a new genus.

(5) The Degree of Development of the Gizzard: The vestigial nature of the gizzard in some genera and its strong development in others is a valuable generic character, e.g., the two genera Microscolex and Rhododrilus are distinguished by the vestigial nature of the gizzard in the former and by its greater development in the latter.

Specific Characters

The similarities of species within genera of the Megascolecidae are often extremely close, and it is commonly necessary to make use of small differences in internal anatomy to differentiate between closely allied species.

The number and form of the spermathecae and their diverticula are useful and reliable specific characters. A great diversity is found within a genus, but within a species the constancy of form, particularly of the diverticula, is a character of great systematic importance.

Another constant and reliable specific character is the form of the penial chaetae which occur in association with the prostate glands in many species of the Megascolecidae. Pickford (1937) found the form of the penial chaetae of great systematic value in the Acanthodriline earthworms of South Africa.

In some cases the number of testes is a useful specific character, e.g. in Diporochaeta chathamensis Benham (1900) there is only one pair of testes, in segment xi, in contrast to the more general characteristic of two pairs, one in segment × and one in segment xi, found in this genus.

Pickford (1937) made use of the nature of the junction between the nephridial tubule and the nephridial vesicle to separate the species of some genera into groups.

The characters discussed above are useful and have been found to be reliable. Other characters whose reliability is more doubtful have been used for the distinction of some species. Beddard (1892) distinguished the two species Octochaetus multiporus and O. thomasi by the difference in their size, the former species being very large and the latter rather smaller, although he gave no measurements of O. thomasi for comparison with O. multiporus. These species were founded by Beddard on a small number of specimens and it is doubtful whether the distinction between the two can be upheld, since the author has observed that within a single species a great variation in size is frequently found among mature specimens. Benham (1905) made use of the number and position of the tubercula pubertatis to distinguish the species of Dinodriloides annectens (1905) and D. beddardi (1904a). It is doubtful whether this distinction of species can be upheld either, since in Microscolex aucklandicus (1902), Microscolex huttoni (1900) and Rhododrilus besti (1904a) Benham records great variation in the number and position of the tubercula pubertatis and the author has observed similar variation in other species.

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Throughout these papers Roman numerals will be used to denote the segments of the earthworms described (e.g. xvii = segment seventeen; xvii/xviii = septum dividing xvii and xviii) and external intersegmental grooves will be denoted by ordinary numerals, e.g. 7/8, 8/9, etc.

One of the most common genera of earthworms occurring in the Australasian region is the genus Rhododrilus of the sub-family Acanthodrilinae. Nine species of the genus have been described by previous workers, three from the North Island of New Zealand, one from Little Barrier Island, one from the Kermadec Islands, one from Chatham Islands, one from Queensland, and two from the sub-antarctic islands of the New Zealand region. Eleven new species of the genus, all from the North Island of New Zealand, are described in this paper.

The genus was established by Beddard (1889) to include species showing the following characters:

Eight chaetae per segment. Nephridiopores in a single series on each side. Male pores on xviii or xvii or in 17/18; one pair of prostatic pores on xvii. Spermathecal pores one to four pairs, the last pair in 8/9. Gizzard well developed. Two pairs of free testes and funnels in × and xi.

It shows close affinities to Microscolex, from which it differs principally in the possession of a well-developed gizzard (in Microscolex the gizzard is vestigial). Michaelsen (1900) distinguished the two genera, but in 1905 he united Rhododrilus and Microscolex and then in 1907 separated them again and they have remained separate since then. Benham (1909) established a genus Leptodrilus for two species from Auckland and Campbell Islands which are identical with Rhododrilus except that the male and prostatic pores are on xvi instead of xvii. Michaelsen (1923) states, “[this difference] I regard as an abnormality of little systematic moment; in my opinion it is even doubtful whether there is any specific difference between Leptodrilus leptomerus and Rhododrilus cockayni, let alone a difference in genus.” Stephenson (1930) allows the genus Leptodrilus to stand, but it is doubtful whether the differences from Rhododrilus are significant.

One of the species described in this paper (R. disparatus) shows characters atypical of the genus in possessing a small ventro-lateral cluster of micronephridial tubules beside each of the meganephridial tubules in ii–xx. Also in R. intermedius, described in this paper, the ventro-lateral portions of the meganephridial tubules are coiled in a spirillar form, superficially resembling micronephridia. This condition is similar to that found by Benham and Cameron (1913) in Plagiochaeta (Perieodrilus) ricardi and P. montanus. It is regarded by Stephenson (1930) as probably intermediate between the meganephridial and the micronephridial conditions. There is little to distinguish R. disparatus (and to a lesser extent R. intermedius) from the sub-family Octochaetinae, especially since the author has recently discovered a new genus of that sub-family which has the microscolecine arrangement of the male reproductive organs (this genus will be described in a later paper).

The New Zealand species of Rhododrilus may be identified from the following key:

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a1 One pair of spermathecae
  b1 Spermathecae in viii
   c1 Two pairs of hearts R. leptomerus Benh. (1909)
   c2 Four pairs of hearts R. edulis Benh. (1904a)
  b2 Spermathecae in ix
   d1 Penial chaetae absent R. albidus n.sp.
   d2 Penial chaetae present
    e1 Penial chaetae confined to xvii R. similis Benh. (1905a)
    e2 Penial chaetae running through xvii and xviii R. intermedius n.sp.
    e3 Penial chaetae running through xvii–xxi R. besti Benh. (1904a)
    e4 Penial chaetae running through xvii–xxiv
     f1 Meganephridial R. parvus Benh. (1905)
     f2 Micronephridia occurring with meganephridia in ii–xx R. disparatus n.sp.
a2 Two pairs of spermathecae
  g1 Three pairs of hearts R. sutherlandi n.sp.
  g2 Four pairs of hearts
   h1 Two pairs of vesiculae seminales
    i1 Tip of penial chaeta sharply recurved and hook-like R. papaensis n.sp.
     i2 Tip of penial chaeta rounded and smooth R. macroseptus n.sp.
   h2 Three pairs of vesiculae seminales R. benhami n.sp.
a3 Three pairs of spermathecae
  j1 Penial chaeta with smooth rounded tip R. kermadecensis Benh. (1904)
  j2 Penial chaeta with sharp recurved hook-like tip R. cockayni Benh. (1909)
a4 Four pairs of spermathecae
  k1 Dorsal blood vessel paired R. attenuatus n.sp.
  k2 Dorsal blood vessel unpaired
   l1 Laterally directed digitate spermathecal diverticulum R. minimus n.sp.
   l2 Anteriorly directed stout hook-like spermathecal diverticulum R. aduncocystis n.sp.
a5 Five pairs of spermathecae R. robustus n.sp.

R. robustus, by its possession of five pairs of spermathecae, falls outside the definition of the genus given by Stephenson (1930), but this character is not significant and the definition of the genus may be extended to include species having more than four pairs of spermathecae.

The following are descriptions of eleven species of Rhododrilus discovered in the North Island of New Zealand. Type specimens in the author's collection.

Rhododrilus albidus n.sp. (Plate 104, figs. 1–3)

Twenty specimens of this slender, unpigmented earthworm were collected from Taupo sandy silt and Puketitiri sandy silt in Ball's Clearing Forest Reserve, Puketitiri, Hawke's Bay. In its external features the species is rather similar to R. sutherlandi, described by the author from the “gumlands” of North Auckland.

The specimen on which this description is based is 95 mm. in length and 2·75 mm. in diameter, with 119 segments.

The prostomium is tanylobous. The chaetae are eight per segment, arranged in pairs. On xxiv:

ab = cd = 0·5 mm.; aa = 1 mm.; bc = 1·5 mm.; dd = 2 mm.

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The first two segments are longitudinally furrowed. Segment iii and all the segments posterior to iii are biannulate. There is no marked clitellum.

There is a single pair of spermathecal pores at 8/9 in line with the chaetae ab. The pores have very prominent tumid lips. There is a pair of female pores on xiv anterior to the chaeta a. A single pair of prostatic pores occurs on xviii. Each pore is situated on a prominent brownish dome-like papilla in line with the chaetae ab. Tubercula pubertatis occur on xii in the form of a transverse tumid ridge extending from chaeta b of one side to chaeta b of the other side, and at 19/20, 20/21 and 21/22 in the form of a pair of small papillae in each intersegmental furrow in line with the ventral couples of chaetae.

Nephridiopores commence on ii and occur in a single series on each side of the body in line with the chaetae c.

Internal Anatomy (Plate 104, fig. 2)

There are no specially thickened septa.

Alimentary Canal. The pharynx is small, rounded and strongly muscular and occupies the first four segments. There is a short thinwalled proventriculus in v joining the pharynx to an elongate, thinwalled, muscular gizzard in vi. The oesophagus extends from vii to xvii and has a single pair of small, rounded calciferous glands in xiii. The intestine commences in xviii and has a typhlosole.

Vascular System. The dorsal blood vessel is unpaired anteriorly, but becomes paired at xii/xiii, the two vessels remaining distinct throughout the remainder of their length. There are three pairs of dilated hearts in x, xi and xii.

Reproductive System. There are two pairs of minute testes and funnels in × and xi, and a single pair of small ovaries in xiii. A single pair of spermathecae occurs in ix. Each consists of a flattened disc-like sac opening to the exterior by a narrow duct, with a small ovoidal diverticulum opening by a slender duct into the spermathecal duct, close to the body wall. (Plate 104, fig. 3.) There is one pair prostates in xvii. They are convoluted tubular organs extending back through xvii and xviii into xix, where they terminate. I could find no penial chaetae. Two pairs of vesiculae seminales occur in xi and xii. They are made up of small round masses of vesicular tissue held together by a sheet of connective tissue.

The nephridia are very small and much convoluted and lie on the lateral aspects of the body wall in each segment.

In its small size and general external features this species fairly closely resembles R. similis Benham (1905a), R. parvus Benham (1905), and R. sutherlandi. However, it differs from R. similis in possessing a pair of prominent calciferous glands in xiii (R. similis has no oesophageal glands), from R. parvus in having no penial chaetae (R. parvus has extremely elongate penial chaetae in a sac extending through eight segments), and from R. sutherlandi in the possession of only one pair of spermathecae (R. sutherlandi has two pairs).

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Rhododrilus intermedius n.sp. (Plate 105, figs. 1–4)

A number of specimens of this large brown earthworm were found at depths of 0–12 in. in Mokau sandy loam under tawa, ferns and bracken on the steep sides of a gully ten miles south of Ohura beside the Stratford-Ohura road. Superficially the species might be confused with some Octochaetinae. The clitellum has a slight purplish tinge, but is otherwise not obviously differentiated from the adjacent segments and covers the dorsal and lateral aspects of segments xii–xviii. The specimen described below is 228 mm. in length and 10·5 mm. in diameter and has 175 segments.

The prostomium is epilobous.

There are eight chaetae per segment, arranged in pairs. On xxiv: ab = 2 mm.; cd = 3 mm.; bc = 4·5 mm.; aa = 4 mm.; dd = 9 mm.

A single pair of spermathecal pores with prominent tumid lips occurs in the groove 8/9, one on each side in line with chaeta b. The female pores open on xiv, a pore on each side slightly anterior and lateral to chaeta a. On xvii there is a very prominent conical papilla on each side in line with the chaetae ab and the combined male and prostatic pores open to the exterior at the apices of the papillae. Two penial chaetae can be seen projecting from each pore. There are two pairs of small tubercula pubertatis, a pair on xix and a pair on xx, taking the form of a small white oval pad posterior to the chaetae ab on each side of each of the segments.

Nephridiopores commence on ii and occur in a single series on each side of the body, in line with chaeta c. The first dorsal pore lies in the intersegmental groove 12/13.

Internal Anatomy (Plate 105, fig. 2)

Septum vi/vii is slightly thickened and muscular and the septa vii/viii, viii/ix, ix/x, x/xi, xi/xii, xii/xiii and xiii/xiv are greatly thickened and strongly muscular. Narrow longitudinal muscle bands pass through the coelom and join the septa vi/vii to xiii/xiv. The last oleven septa of the body are also much thickened and muscular.

Alimentary Canal. The pharynx occupies segments i–iv. There is a short, thin-Walled proventriculus in v and a very thick-walled muscular gizzard in vi. The oesophagus extends from vii to xvi and there are no oesophageal glands. The intestine commences in xvii.

Vascular System. The dorsal blood vessel is unpaired throughout its length. A slender supra-intestinal vessel lies immediately under the dorsal blood vessel and extends through segments x–xiii. Four pairs of dilated hearts, a pair in each of x, xi, xii and xiii arise from the supra-intestinal vessel.

Reproductive System. There are two pairs of small lobate testes, a pair in × and a pair in xi, attached to the anterior septum of the segment close to the ventral midline. The two vasa deferentia of each side remain separate, but lie close together as they pass along the ventro-lateral aspect of the peritoneum to their point of entry into the prostatic duct. The paired ovaries are attached to the anterior septum of xiii in a similar position to the testes. The ovaries are very thin transparent laminar organs with the ova arranged like strings of

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beads along the lamina. There is a single pair of spermathecae in ix. Each consists of a large ovoidal sac opening by a wide duct to the exterior. A thick digitate diverticulum opens into the spermathecal duct just below the spermathecal sac. (Plate 105, fig. 3.) The prostates are convoluted tubular organs arising from a thick muscular duct in xvii and following an irregular course to their termination in xxi. A sac containing penial chaetae lies against the medial aspect of each prostatic duct and is attached by strong muscle fibres passing through septum xvii/xviii to their insertion on the dorso-lateral aspect of the peritoneum close to the posterior septum of xviii. The penial chaetae have slender gently curved shafts and a slightly recurved blunt tip. Distally, for about a third of their length, they are armed with rows of minute spines which point towards the tip of the chaeta (Plate 105, fig. 4.) There are two pairs of botryoidal vesiculae seminales, a pair in xi and a pair in xii, surrounding the oesophagus in those segments.

Meganephridia are present in every segment except the first. The tubules are very slender and at first sight it appears that there are both meganephridia and micronephridia present in each segment. However, close examination shows that the meganephridium consists of three distinct parts:

(i)

A slender tubule arises from the small nephridial funnel and passes down the lateral margin of the coelom to

(ii)

a complex coiled tubular portion of the nephridium close to the ventral nerve cord. Here the tubule is thrown into a series of tightly wound spirals which project into the coelom and superficially closely resemble micronephridia.

(iii)

The tubule passes from the coiled portion straight back up the lateral aspect of the peritoneum to open to the exterior through a very small vesicle which is little more than a slight bulb in the end of the tubule.

Remarks. The species is most closely similar to R. edulis, but the spermathecae of R. edulis are in viii, while those of R. intermedius are in ix.

Rhododrilus disparatus (Plate 106, figs. 1–3)

Several specimens of this large sienna-brown earthworm were collected from unmelanised sands in a recent flood deposit beside a small stream three miles south of Tolaga Bay and others from a silt loam under native rain-forest (ngaio, titoki) ten miles east of Otoko on the Gisborne-Opotiki road.

A mature specimen measures 197 mm, in length and 6 mm. in diameter and has 203 segments. It is sienna-brown dorsally, paler ventrally, and has a greyish-brown clitellum, covering xiv–xviii and part of xiii down to the level of chaeta a (5 ½ segments). The prostomium is epilobous. There are eight chaetae per segment, arranged in pairs. On xxiv:

ab = cd = lmm.; aa = 2 mm.; bc = 2·5 mm.; dd = 4 mm.

There is a single pair of small spermathecal pores at 8/9 in line with chaeta b. A pair of female pores occurs on xiv, slightly anterior to chaeta a. The single pair of prostatic pores are situated on the apices of a pair of prominent dome-like papillae, in line with the chaetae ab

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on xvii. Male pores are not visible externally. The nephridiopores are in a single series anterior to chaeta c, commencing on ii.

Prominent paired tubercula pubertatis occur in line with the chaetae ab at the posterior margins of segments ix and x, and in the intersegmental grooves 19/20, 20/21 and 21/22.

Internal Anatomy (Plate 106, fig. 2)

The septa vii/viii, viii/ix, ix/x, x/xi, xi/xii and xii/xiii are muscular and thickened.

Alimentary Canal. A rounded pharynx, covered dorsally and laterally by tufted salivary glands, occupies the first four segments. There is a thin-walled proventriculus in v, joining the pharynx to a large, thick-walled muscular gizzard in vi. The oesophagus extends from vii to xv and lacks oesophageal glands. The intestine commences in xvi. It is wide and thin-walled and has a marked typhlosole.

Vascular System. The dorsal blood vessel is unpaired. There is a short, narrow, supra-intestinal blood vessel running through segments x–xiii and giving rise to four pairs of dilated hearts in those four segments. The hearts arise from the supra-intestinal vessel as very narrow vessels, but dilate close to their origin into very wide vessels.

Reproductive System. There are two pairs of testes and their funnels in × and xi, and a single pair of ovaries with their funnels in xiii. The testes and ovaries are similar in form, dorso-ventrally flattened racemose structures attached to the anterior septa of their segments. There is one pair of spermathecae in ix. Each consists of a roughly ovoidal sac with a long hose-like diverticulum arising from the anterior aspect of its duct and describing a semicircle around the lateral aspect of the spermathecal sac, terminating behind the spermathecal sac in a dorsally directed portion (Plate 106, fig. 3). A pair of very long tubular prostates extend from xvii to xxvii, arising from narrow ducts in xvii. The distal portion of each prostate is thrown into coils. An elongate sac containing the penial chaetae lies on the medial aspect of each prostate and extends from xvii to xxiv. An individual penial chaeta removed from the sac is 5 mm. long. It is thus much shorter than the sac in which it is contained. It has an elongate, slightly irregular, gently curved shaft, with a gently recurved tip terminating in a point. There are two pairs of botryoidal vesiculae seminales in xi and xii surrounding the lateral and part of the dorsal aspects of the oesophagus.

The arrangement of the nephridia is most unusual for this genus. In segments ii–xx, small, coiled, paired meganephridia open to the exterior beside chaeta c, but close to the ventral nerve cord are found small clusters of micronephridial tubules. Posterior to xx, the meganephridia are large and no micronephridia occur.

Remarks. This species is obviously closely related to other species of Rhododrilus [especially to R. besti Benham (1904) and R. similis Benham (1905a)] but the co-existence of micronephridia and meganephridia in the first twenty segments poses a taxonomic problem of some importance. An earthworm possessing all the characters of Rhododrilus, but being partly or wholly micronephridial, should, according to Michaelsen's definitions of the sub-families of the Megascolecidae,

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be placed in the sub-family Octochaetinae. This raises a question as to the value of an arbitrary division of sub-families based on the arrangement of nephridia and it would seem that in the case of the present species this might be disregarded. In other genera (especially Megascolides, Megascolex and Spenceriella) a variety of arrangements of meganephridia and micronephridia is found within the genera and there is a common tendency throughout the family Megascolecidae for a change from the meganephridial to the micronephridial condition. The New Zealand genera of the Octochaetinae could have evolved independently from the New Zealand Acanthodrilinae by a change from the meganephridial to the micronephridial condition and the discovery of a species of Rhododrilus which has some micronephridia co-existent with meganephridia shows this process in operation.

Rhododrilus sutherlandi n.sp. (Plate 107, figs. 1–4)

Twelve specimens of this slender worm were collected by Mr. C. F. Sutherland from subsoil in a pasture two miles north-east of Tutamoe, beside the Whangarei-Kaikohe road. The specimen on which this description is based is 143 mm. in length and 2 mm. in diameter. In the posterior region the margins of the segments are ill-defined, but there are about 150 segments. The clitellum is developed only dorsally and laterally, over xiii–xvii, and is very thick. The prostomium is epilobous.

There are eight chaetae per segment, lumbricine in arrangement. On xi the arrangement is as follows:

ab = 0·5 mm.; cd = 0·5 mm.; bc = 0·75 mm.; aa = 0·75 mm.; dd = 0·75 mm.

There are two pairs of spermathecal pores, a pair at 7/8 and a pair at 8/9, in line with chaeta b. A single pair of female pores is present on xiv; each pore lies medial and slightly anterior to chaeta b. A pair of prostatic pores is present on xvii. Each pore is situated on a prominent white papilla in line with the chaetal intervals ab on the same side. A pair of extremely elongate, curved, slender penial chaetae originate close to each prostatic pore and project anterolaterally. Male pores are not visible externally.

The tubercula pubertatis are the most striking character of the species, taking the form of a pair of round tumid pads on each of x, xi, xiv and xix. Each tuberculum is situated in line with the chaetal intervals ab on the same side. An unpaired similar tuberculum occurs on ix on the left side, and on xv on the right side.

Nephridiopores occur in a single series on each side, each pore lying anterior to chaeta c.

Internal Anatomy (Plate 107, fig. 2)

There are no thickened septa.

Alimentary Canal. The pharynx is globular and muscular and occupies the first four segments. To its dorsal surface is attached a covering of salivary glands. The gizzard, which is elongate and thick walled, is confined to v, but appears superficially to occupy v, vi and vii and the anterior portion of viii. The oesophagus extends from vi to xvi, and has a single pair of calciferous glands in xiii. The intestine commences in xvii, is very narrow and has a marked typhlosole.

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Vascular System. The dorsal blood vessel is single throughout. There are three pairs of hearts in x, xi and xii.

Reproductive System. There are two pairs of testes, a pair in x and a pair in xi, and the vas deferens of each side opens close to the prostatic duct in xvii. A single pair of ovaries is present in xiii and very prominent oviducts lead posteriorly from the funnels in xiii and open to the exterior in xiv. There are two pairs of spermathecae, a pair in viii and a pair in ix. Each spermatheca consists of a large ovoidal sac, with a rounded diverticulum extending into the adjacent anterior segment and opening into the spermathecal duct (Plate 107, fig. 3). A pair of elongate convoluted tubular prostates is present. Each prostate arises from a narrow coiled duct in xvii and extends posteriorly through xvii and xviii to xix, where it terminates. An elongate sac containing several penial chaetae lies close to each prostatic duct. Each penial chaeta has a slender gently curved shaft, which is sharply recurved distally (Plate 107, fig. 4). There are two pairs of vesiculae seminales surrounding the oesophagus, a pair in xi and a pair in xii. Each vesicula is made up of small nodules of vesicular tissue held together by a sheet of connective tissue.

Small coiled nephridia are present in each of the segments except the first.

Remarks. This species is similar in its general form to R. kermadecensis Benham (1904) and to R. parvus Benham (1905), but differs from these species in having two pairs of spermathecae (R. kermadecensis has three pairs and R. parvus one pair) and also in other points of internal anatomy.

Ecological Notes. R. sutherlandi was collected from the subsoil horizon of the Tutamoe clay loam, under poor pasture dominantly browntop (Agrostis tenuis Sibth.) with stunted bracken (Pteridium aquilinum var. esculentum Hook. f.), used seasonally for extensive cattle grazing.

In an adjacent area of rain-forest, composed mainly of Weinmannia sylvicola Soland., Knightia excelsa R. Br., Phyllocladus glaucus Carr. and tree-ferns, R. sutherlandi was distributed throughout the topsoil and the subsoil. This suggests that the destruction of the native forest to provide rough grazing, when unaccompanied by liming and top-dressing, causes sufficient alteration in the soil environment to initiate a series of changes in the endemic earthworm fauna, in the first stage of which the endemic species retreat into the subsoil. A second endemic species, Megascolex sp., which was present under the forest conditions, had completely disappeared from under the rough pasture. The only earthworm inhabiting the topsoil of this pasture was Octolasium cyaneum. Pasture areas which have been top-dressed show the following progressive stages:

(a)

In lightly top-dressed pastures no endemic species are found and the only earthworms present are Lumbricus rubellus, Octolasium cyaneum and Allolobophora caliginosa, in varying numerical proportions.

(b)

In heavily top-dressed areas Lumbricus rubellus is rare, and the only species commonly found is Allolobophora caliginosa, which is often present in fairly large numbers.

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It would seem that endemic species cannot adapt themselves readily to marked changes in soil conditions. The introduced species, especially Allolobophora caliginosa, have a wider range of tolerance.

Rhododrilus papaensis n.sp. (Plate 108, figs. 1–4)

A single specimen was collected from soil derived from mudstone under a small forest remnant near the top of the Gentle Annie Hill, three miles east of Wairenga-o-Kuri beside the Gisborne-Wairoa road.

The specimen is 126 mm. in length, with 194 segments, and is 4 mm. in diameter. It is pale yellowish-brown in colour with a sienna brown clitellum developed over the entire surface of xiii to xvii except for the area of xvii lying between the prostatic papillae. The prostomium is proepilobous. There are eight chaetae on each segment, arranged in four pairs. On xxiv:

ab = 0·75; cd = 1·5 mm.; bc = 2 mm.; aa = 2 mm.; dd = 4 mm.

Spermathecal pores are not visible externally. A small female pore is situated slightly anterior and medial to chaeta a on each side of xiv. The prostatic pores are situated on the apices of a pair of small rounded papillae on xvii. The papilla of each side lies in line with the chaetal interval ab of that side. A longitudinal groove is visible on each papilla, from the prostatic pore to the anterior margin of xviii, terminating at the male pore on each side of xviii.

Nephridiopores commence on ii and lie in a single series on each side of the body, close to the anterior margins of the segments and anterior to chaeta c on each side of the segments.

Paired tubercula pubertatis are situated on xviii, in the form of a small rounded pad posterior to chaeta b on each side.

Internal Anatomy (Plate 108, fig. 2)

The septa vi/vii, vii/viii, viii/ix, ix/x, x/xi, xi/xii and xii/xiii are muscular and thickened.

Alimentary Canal. A small globular pharynx occupies the first four segments. There is a short, thin-walled proventriculus in v and a thick-walled muscular gizzard in vi. The oesophagus extends from vii to xv. There are no oesophageal glands. The intestine commences in xvi. It is thin-walled and the typhlosole is not strongly developed.

Vascular System. The dorsal blood vessel is unpaired. Four pairs of dilated hearts originate from the dorsal vessel in × to xiii. The hearts of xiii are smaller in diameter than those of × to xii.

Reproductive System. There are two pairs of testes, a pair in x and a pair in xi. Each testis takes the form of a cluster of thread-like processes attached to the anterior septum of its segment close to the median ventral line. A pair of ovaries is situated in xiii. The ovaries are similar in form to the testes. There are two pairs of spermathecae, a pair in viii and a pair in ix. Each is in the form of an ovoidal sac with an anterior digitate diverticulum, and opens to the exterior at the extreme anterior margin of its segment in line with the chaetal interval ab. (Plate 108, fig. 3.)

A pair of tubular prostates is present. Each arises from a narrow duct in xvii and follows a convoluted course through xviii, xix, and xx into xxi, where it terminates. A transparent sac containing penial

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Fig. 1—Rhododrilus albidus. Ventral aspect, segments i–xxii.
Fig. 2—R. albidus. Dissection from the dorsal aspect.
Fig. 3—R. albidus. Left spermatheca, lateral aspect.

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Fig. 1—R. intermedius. Ventral aspect, segments i–xxi.
Fig. 2—R. intermedius. Dissection from the dorsal aspect.
Fig. 3—R. intermedius. Right spermatheca, anterior aspect.
Fig. 4—R. intermedius. a, Penial chaeta. b, Tip of penial chaeta.

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Fig. 1—R. disparatus. Ventral aspect, segments i–xxii.
Fig. 2—R. disparatus. Dissection from the dorsal aspect.
Fig. 3—R. disparatus. Left apermatheca, lateral aspect.

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Fig. 1—R. sutherlandi. Ventral aspect, segments i–xx.
Fig. 2—R. sutherlandi. Dissection from the dorsal aspect.
Fig. 3—R. sutherlandi. Left posterior spermatheca, lateral aspect.
Fig. 4—R. sutherlandi. Penial chaeta.

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Fig. 1—R. papaensis. Ventral aspect, segments i–xix.
Fig. 2—R. papaensis. Dissection from the dorsal aspect.
Fig. 3—R. papaensis. Left posterior spermatheca, medial aspect.
Fig. 4—R. papaensis. Penial chaeta.

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Fig. 1—R. macroseptus. Ventral aspect, segments i–xxii.
Fig. 2—R. macroseptus. Dissection from the dorsal aspect.
Fig. 3—R. macroseptus. Right posterior spermatheca, anterior aspect.
Fig. 4—R. macroseptus. Penial chaeta.

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Fig. 1—R. benhami. Ventral aspect, segments i–xxii.
Fig. 2—R. benhami. Dissection from the dorsal aspect.
Fig. 3—R. benhami. Right posterior spermatheca, anterior aspect.
Fig. 4—R. benhami. Penial chaeta.

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Fig. 1—R. attenuatus. Ventral aspect, segments i–xviii.
Fig. 2—R. attenuatus. Dissection from the dorsal aspect.
Fig. 3—R. attenuatus. Right posterior spermatheca, lateral aspect.
Fig. 4—R. attenuatus. Penial chaeta.

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Fig. 1—R. minimus. Ventral aspect, segments i–xviii.
Fig. 2—R. minimus. Dissection from the dorsal aspect.
Fig. 3—R. minimus. Right posterior spermatheca, anterior aspect.
Fig. 4—R. minimus. Penial chaeta.

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Fig. 1—R. aduncocystis. Ventral aspect, segments i–xxi.
Fig. 2—R. aduncocystis. Dissection from the dorsal aspect.
Fig. 3—R. aduncocystis. Right posterior spermatheca. posterior aspect.
Fig. 4—R. aduncocystis. a. Penial chaeta, b, Tip of penial chaeta.

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Fig. 1—R. robustus. Ventral aspect, segments i–xx.
Fig. 2—R. robustus. Dissection from the dorsal aspect.
Fig. 3—R. robustus. Left spermatheca of vii, anterior aspect.
at. = spermathecal atrium: e.g. cerebral ganglion; ch. = chaeta; d.b.v. = dorsal blood vessel; d.div. = duct of spermathecal diverticulum; div. = spermathecal diverticulum; f.p. = female pore; g. = gizzard; h. = heart; int. = intestine; m. = month; mn. = micronephridial tubule; m.p. = male pore; n. meganephridial tubule; o. = ovary; od. = oviduct; oe. = oesophagus; oe.gl. = oesophageal gland; o.f. = ovarian funnel; p. = prostate; pap. = papilla; p.ch. = penial chaeta; p.d. = prostatic duct; peri. = peristomium; ph. = phyrnx; p.p. = prostatic pore; pr. = prostomium; pv. = proventriculus; s. = septum; sac = sac = containing the penial chaetae; sal.gl. = salivary gland; s.l.v. = supra-intestinal vessel; sp. = spermathecal sac; sp.d. = spermathecal duct; sp.p. = spermathecal pore; t. = testis; t.f. = testicular funnel; t.pub. = tuberculum pubertatis; v.s. = vesicula seminalis.

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chaetae lies close to each prostatic duct in xvii. Each penial chaeta has an elongate gently curved shaft and is very sharply recurved distally (Plate 108, fig. 4). There are two pairs of botryoidal vesiculae seminales, a pair in xi and a pair in xii.

Paired meganephridia are present in every segment except the first.

Rhododrilus macroseptus n.sp. (Plate 109, figs. 1–4)

This is a large earthworm species, fairly common in virgin soils in the hills near the western sea coast of the Waikato, around Raglan and Kawhia. It is light pink when living, colourless when killed in alcohol. The specimen described below was collected from a small remnant of native forest near the crest of the main ridge of the Raglan Range about a mile south of the highest point on the Hamilton-Raglan road. It is 386 mm. in length and 11 mm. in diameter behind the clitellum, and has 236 segments. All the segments have secondary annulations, the number of annuli in each segment varying from two to seven. The prostomium is prolobous. There are eight chaetae on each segment, arranged in four pairs. On xxiv the arrangement is as follows:

ab = 2 mm.; cd = 3 mm.; aa = 5 mm.; bc = 6 mm.; dd = 10·5 mm. The clitellum completely surrounds segments xiv–xvii and extends over the posterior portion of xiii and the anterior portion of xviii. There are two pairs of spermathecal pores, a pair at 7/8 and a pair at 8/9, in line with chaeta b on each side. The female pores are situated on xiv [ unclear: ] , one on each side, anterior and slightly lateral to chaeta a. The prostatic pores are situated on top of a pair of prominent conical papillae, one on each side of xvii in the position of the pair of chaetae ab. A penial chaeta can be seen projecting from the apex of one of the prostatic papillae.

The tubercula pubertatis take the form of a pair of small white pads, one on each side of the ventral mid-line close to the hinder margins of segments x, xi, xiv, xv, xix and xx. A smaller unpaired tuberculum occurs on the left hand side of xxi, close to the hinder margin and to the ventral mid-line.

Nephridiopores commence on ii and occur in a single series on each side in line with chaeta c.

Internal Anatomy (Plate 109, fig. 2)

Septa vi/vii, vii/viii, viii/ix, ix/x, x/xi and xi/xii are very greatly thickened and extremely muscular, while septa xii/xiii, xiii/xiv and xiv/xv are slightly thickened.

Alimentary Canal. The pharynx is large and muscular and occupies the first five segments. There is a fairly slender, thick-walled, muscular gizzard in v and vi. The oesophagus extends from vii to xv and there is a very prominent pair of calciferous glands in xiv, arising as large dilatations from the lateral walls of the oesophagus. The intestine commences in xvi.

Vascular System. The dorsal blood vessel is unpaired throughout its length. A slender supra-intestinal blood vessel runs along the dorsal aspect of the oesophagus beneath the dorsal blood vessel in x–xiii and gives rise to a pair of widely dilated hearts in each of those segments.

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Reproductive System. There are two pairs of testes, a pair in x and a pair in xi, and a pair of ovaries in xiii. The testes and ovaries are similar in appearance, consisting of clusters of threadlike processes attached to the anterior septa of their segments, one cluster on each side close to the ventral mid-line. There are two pairs of spermathecae, a pair in viii and a pair in ix. Each spermatheca consists of a large flattened oval sac, lying closely pressed against the ventro-lateral aspect of the body-wall and a small pyriform diverticulum lying against the lateral aspect of the spermathecal sac and opening by a short narrow duct into the spermathecal duct. (Plate 109, fig. 3.) The prostates are long, coiled, tubular organs arising one on each side of xvii, from a slender coiled duct and following a convoluted course through the lateral coelomic spaces of xvii, xviii, xix and xx to terminate in xxi. A muscular sac containing a pair of penial chaetae lies between the prostatic duct and the peritoneum and is attached to the dorso-lateral aspect of the peritoneum. A penial chaeta has a long, very gently curved shaft with a rounded tip. (Plate 109, fig. 4.) There appear to be very small spines on the shaft, but they are so small that it is difficult to distinguish them. There are two pairs of finely racemose vesiculae seminales, a pair in xi and a pair in xii.

The nephridia are similar in form to those of R. intermedius, the tubule being thrown into a number of slender loops which superficially resemble micronephridia.

This species shows many similarities to R. intermedius, but the possession of two pairs of spermathecae (R. intermedius has only one pair) is a convenient point of reference to distinguish the two species.

Rhododrilus benhami n.sp. (Plate 110, figs. 1–4)

A number of specimens of this light brown earthworm were collected at depths of 0–10 in. from Westmere si.l. in a small remnant of native forest (ngaio, titoki, kawakawa) on the south side of the Wanganui-Hawera road between Maxwell and Nukumaru.

The specimen described below is 57 mm. in length and 3 mm. in diameter and has 108 segments. The prostomium is tanylobous. The clitellum covers the whole area of xiv–xvi and the anterior half of xvii. There are eight chaetae per segment, arranged in four pairs. On xxiv the arrangement is as follows:

ab = cd = 1 mm.; bc = 1·25 mm.; aa = 1·25 mm.; dd = 3 mm. There are two pairs of spermathecal pores, a pair at 7/8 and a pair at 8/9, in line with chaeta a. A pair of female pores occurs on xiv, a pore anterior and slightly medial to chaeta a on each side. The prostatic pores are on small rounded papillae, one on each side of xviii in line with the chaetae ab. There is a small male pore on each side of xvii on the extreme posterior margin of the segment in line with chaeta b. There is a single pair of small tubercula pubertatis in the form of a small rounded pad posterior to chaeta b on each side of xix.

The nephridiopores occur in a single series on each side of the body, in line with chaeta c.

Internal Anatomy (Plate 110, fig. 2)

There are no specially thickened septa.

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Alimentary Canal. The pharynx occupies the first four segments. There is a short, thin-walled proventriculus in v, followed by a long, thick-walled, muscular gizzard in vi. The oesophagus extends from vii to xv and there are no oesophageal glands. The intestine commences in xvi and has no typhlosole.

Vascular System. The dorsal blood vessel is unpaired. There are four pairs of dilated hearts, a pair in each of x, xi, xii and xiii.

Reproductive System. There are two pairs of testes, a pair in x and a pair in xi. Each testis consists of a group of long, tubular processes originating from a point close to the ventral mid-line on the anterior septum of the segment and projecting freely into the coelom of the segment. The ovaries occupy similar positions in xiii, but are smaller and more compact organs. There are two pairs of spermathecae, a pair in viii and a pair in ix. Each spermatheca consists of a long sausage-shaped sac opening by a narrow duct to the exterior. A smaller sausage-shaped diverticulum lies lateral to the spermathecal sac and opens into the spermatheca close to the spermathecal duct (Plate 110, fig. 3). The prostates are long, uncoiled, tubular organs arising in xvii and passing back along the ventro-lateral aspects of the body-wall, terminating in xxiv. A pair of penial chaetae, contained in a fibrous sac, lies close to the lateral aspect of each prostate, extending through xvii and xviii. The penial chaetae have slender shafts, bent fairly sharply in the middle, and have flattened tips terminating in a point (Plate 110, fig. 4). There are three pairs of racemose vesiculae seminales, a pair in each of x, xi and xii, surrounding the lateral and dorsal aspects of the oesophagus.

Paired meganephridial tubules occur in every segment except the first. They are slender and tightly coiled.

Rhododrilus attenuatus n.sp. (Plate 111, figs. 1–4)

Common at depths of 16 to 20 inches in the subsoil of clay soils in the northern regions of North Auckland is a slender unpigmented species of Rhododrilus which the author has named R. attenuatus. The species shows close similarities to R. sutherlandi from Whangarei, but there are certain marked differences in its internal anatomy which serve to distinguish it from that species.

The specimen on which this description is based was collected from Mangonui clay near Mangonui at a depth of 18 inches. It is 79 mm. in length and 2 mm. in diameter and has 145 segments. The prostomium is tanylobous. There is no marked clitellum, but the segments xii to xviii are lightly pigmented. The chaetae commence on ii and are lumbricine in arrangement. On xxiv the arrangement is as follows: ab = cd = 0·75 mm.; aa = 1·25 mm.; bc = 1 mm.; dd = 1·25 mm. Ventral chaetae are absent on xvii, but slender penial chaetae project close to the prostatic pores on that segment.

There are four pairs of spermathecal pores, a pair each at 5/6, 6/7, 7/8 and 8/9 in the line of the chaetal intervals ab. There is a pair of female pores on xiv. Each pore lies anterior to the corresponding chaeta a, on each side. A pair of prostatic pores occurs on xvii; each pore is situated on a small, round, flattened papilla in the line of the chaetal intervals ab. The male pores are not visible externally. The

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tubercula pubertatis are similar to those of R. sutherlandi, taking the form of pairs of round tumid pads, a pair on × and a pair on xi in line with the chaetal intervals ab on the corresponding side. There is a similar single tuberculum on xviii, on the right side.

Nephridiopores commence on ii and are present in a single series on each side, anterior to chaetae c.

Internal Anatomy (Plate 111, fig. 2)

There are no specially thickened septa.

Alimentary Canal. The pharynx is rounded and muscular and occupies the first four segments. An elongate muscular walled gizzard lies in v. The oesophagus extends from vi to xviii and has a single pair of small calciferous glands in xiii. The intestine commences in xix. The diameter of the intestine in xix is almost the same as that of the oesophagus, but it increases in the three proximal posterior segments, until in xxii it is about twice that of the oesophagus. The intestine is very thin walled and has a typhlosole.

Vascular System. The dorsal blood vessel is paired throughout. There are three pairs of dilated hearts, a pair each in x, xi and xii.

Reproductive System. There are two pairs of testes, a pair in x and a pair in xi, and a pair of lobate ovaries in xiii. There are four pairs of spermathecae, a pair each in vi, vii, viii and ix. Each spermatheca is in the form of a spheroidal sac opening to the exterior by a narrow duct. An ovoidal diverticulum projects anteriorly from the anterior aspect of the spermathecal duct into the adjacent anterior segment. (Plate 111, fig. 3.) A single pair of convoluted tubular prostates is present. Each prostate arises from a narrow muscular duct in xvii and extends posteriorly through xvii and xviii into xix where it terminates. An elongate sac containing several penial chaetae lies close to each prostatic duct in xvii. Each penial chaeta is elongate and slender, with a gently curved shaft and a recurved flattened tip. (Plate 111, fig. 4.) Two pairs of racemose vesiculae seminales are present, a pair in xi and a pair in xii, situated lateral to the oesophagus in each of these segments.

A pair of small coiled nephridia occurs in each segment except the first.

Remarks. There is a very close similarity between this species and R. sutherlandi, but it is distinct in various points of internal anatomy. The intestine of R. attenuatus commences in xix; that of R. sutherlandi commences in xvii. The dorsal blood vessel of R. attenuatus is paired; that of R. sutherlandi is single. R. attenuatus has four pairs of spermathecae; R. sutherlandi has two pairs. The spermathecal diverticulum of R. attenuatus is ovoidal and that of R. sutherlandi is elongate. The combination of these differences in internal anatomy is sufficient to justify the differentiation of R. attenuatus as a species distinct from R. sutherlandi, although superficially they are very similar and are found in similar habitats.

Rhododrilus minimus n.sp. (Plate 112, figs. 1–4)

This species is common in areas of native forest in the Gisborne district. Superficially it is similar to R. albidus, but a close examination

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shows it to be distinct from that species. It is a small unpigmented worm and when killed in alcohol is pale greyish-white.

The specimen described was collected from a heavily gleyed sandy loam in Grey's Bush, a few miles from Gisborne on Ormond road. It is 54 mm. in length, with 118 segments and has a diameter of 2 mm.

The prostomium is tanylobous. There are eight chaetae per segment, arranged in pairs. On xxiv:

ab = 0·5 mm.; cd = 0·75 mm.; bc = 0·75 mm.; aa = 1 mm.; dd = 1·25 mm.

The spermathecal pores are not visible externally, but there are four pairs of spermathecae, a pair in each of vi, vii, viii and ix and their ducts can be traced to the intersegmental furrows 5/6, 6/7, 7/8 and 8/9 respectively. There is a pair of female pores on xiv, a pore anterior to chaeta a on each side. A pair of prostatic pores is situated on xvii, each pore opening at the apex of a small papilla in line with the chaetal interval ab. The prostates can be seen through the lateral and dorso-lateral aspects of the body-wall, extending from xvii to xxii. The male pores lie directly behind the prostatic pores in a small tumid area on the extreme anterior margin of xviii. There is no marked clitellum.

The tubercula pubertatis take the form of a pair of small oval glandular pads, posterior to the chaetal interval ab on the hinder margins of ix, × and xi, and there is an unpaired transverse tuberculum at the hinder margin of xii, extending from the line of chaeta b on one side to the same line on the other side.

There is a pair of nephridiopores on each segment except the first. The pores lie in a single series on each side, in line with chaeta c.

Internal Anatomy (Plate 112, fig. 2)

There are no specially thickened septa.

Alimentary Canal. A globular pharynx with slender extrinsic muscles occupies i–iv. The pharynx opens into a short proventriculus in v and the proventriculus opens into a long thick-walled muscular gizzard in vi. The oesophagus extends from vii to xv and there are no oesophageal glands. The intestine commences in xvi.

Vascular System. The dorsal blood vessel is unpaired throughout its length. There are three pairs of dilated hearts in segments x, xi and xii.

Reproductive System. The testes are very small paired organs, a pair in × and a pair in xi. There is a pair of minute ovaries in xiii. There are four pairs of spermathecae, a pair in each of the segments vi, vii, viii and ix. Each spermatheca is in the form of an antero-posteriorly flattened irregular sac, opening by a narrow duct to the exterior, with a small lateral digitate diverticulum opening into the lateral aspect of the spermathecal duct. (Plate 112, fig. 3.) The prostates are long, coiled, tubular organs, lying against the dorso-lateral aspects of the peritoneum. Each prostate arises from a shining muscular duct in xvii and extends through the segments xviii, xix, xx, and xxi into xxii. There is a small sac containing penial chaetae beside the prostatic duct in xvii. Each penial chaeta is a slender, pointed spine with its shaft curved in an arc of a circle for most of its length, sharply

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curved distally and terminating in a straight pointed portion (Plate 112, fig. 4). Two pairs of botryoidal vesiculae seminales occur, a pair in xi and a pair in xii, surrounding the lateral aspects of the oesophagus.

There is a pair of slender, coiled meganephridial tubules in each segment except the first.

Rhododrilus aduncocystis n.sp. (Plate 113, figs. 1–4)

This species is common in remnants of native forests on the hills west of the Hauraki Plains. It is dark red-brown in colour, pale ventrally posterior to the clitellum, and has a buff clitellum covering the dorsal and lateral aspects of xiv–xvii and half of xiii and xviii.

The specimen on which this description is based is 114 mm. in length and 5 mm. in diameter and has 127 segments. All the segments except i are biannulate. The prostomium is epilobous. There are eight chaetae per segment, arranged in four pairs on the posterior annulus of each segment. On xxiv their arrangement is as follows:

ab = 0·75 mm.; cd = 1·5 mm.; aa = 2·5 mm.; bc = 2 mm.; dd = 5·5 mm.

Four pairs of spermathecal pores are visible, one pore on each side, in line with chaeta b, in each of the intersegmental furrows 5/6, 6/7, 7/8 and 8/9. There is a single pair of female pores on xiv, one on each side, anterior and slightly lateral to chaeta a. The prostatic pores open to the exterior on xvii, one on each side, in line with chaeta b. There is no well-developed prostatic papilla, but each pore is situated in the centre of a small brown pigmented area. Penial chaetae can be seen projecting from the prostatic pores. The tubercula pubertatis are small white oval pads, one on each side posterior to the pair of chaetae ab, on x, xi, xix and xx.

The first pair of nephridiopores is on ii, anterior to chaeta d and there is a pair on each subsequent segment in a single series on each side anterior to chaeta c. Dorsal pores are visible in each intersegmental furrow posterior to the clitellum, but none could be seen on the clitellum or anterior to it.

Internal Anatomy (Plate 113, fig. 2)

The septa viii/ix, ix/x, x/xi, xi/xii and xii/xiii are thickened and muscular.

Alimentary Canal. The pharynx occupies the first four segments and has numerous strong extrinsic muscles. There is a short, thin-walled proventriculus in v which opens into a large, thick-walled, muscular gizzard in vi and vii. The oesophagus extends from viii to xv and there are no oesophageal glands. The intestine commences in xvi. It is thin walled and lacks a typhlosole.

Vascular System. The dorsal blood vessel is unpaired. A short, slender supra-intestinal vessel lies beneath the dorsal blood vessel in segments × to xii and give rise to three pairs of dilated hearts, a pair in each of x, xi and xii.

Reproductive System. There are two pairs of testes, a pair in x and a pair in xi, and a pair of ovaries in xiii. The testes and ovaries are similar in form, each organ consisting of a group of threadlike structures arising from a point close to the ventral mid-line on the

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anterior septum of its segment. There are four pairs of spermathecae, a pair in each of vi, vii, viii and ix. A typical spermatheca consists of an irregularly oval antero-posteriorly flattened sac and a stout, curved, hook-like diverticulum, projecting forward, both sac and diverticulum opening into a common duct which opens to the exterior in the region of the anterior septum of the segment (Plate 113, fig. 3). The spermathecae of vi are much smaller than those of the subsequent segments and are not typical in form. The spermathecal sac in vi is a slender, tubular, semi-transparent structure, while the diverticulum, though curved into a hook-like form, is not as well developed as are those of the other spermathecae. The prostates are elongate tubular organs, each arising from a slender muscular duct in xvii and extending along the lateral and dorso-lateral aspects of the peritoneum on each side through xviii, xix, and xx into xxi, where each terminates in a coiled portion. A sac containing penial chaetae lies across the medial aspect of the prostatic duct and has strong retractor muscles attaching it firmly to the dorso-lateral aspect of the peritoneum close to the posterior septum of xvii. The penial chaetae have very slender, gently curved shafts, 0·8 mm. in length, and the tips are very slightly recurved and spatulate. (Plate 113, fig. 4, a, b.) There are four pairs of vesiculae seminales, a pair in each of ix, x, xi and xii. Those of xi and xii have the racemose form frequently found in the Megascolecidae and are attached to the anterior septa of their segments, while those of ix and x have the compact sac-like form usually associated with the vesiculae seminales of Lumbricids and are attached to the posterior septa of their segments.

A pair of meganephridial tubules occurs in each segment except the first. The nephridia are slender and extremely convoluted.

Remarks. This species resembles R. similis Benh. in many respects, but may be distinguished by its possession of four pairs of spermathecae (R. similis has only one pair) and four pairs of vesiculae seminales (R. similis has two pairs).

Rhododrilus robustus n.sp. (Plate 114, figs. 1–3)

A number of specimens of this light pink earthworm were collected from Ball's Clearing Forest Reserve, Puketitiri, near Hastings. Some of the specimens were collected from the forest floor under a cover of matai, rimu and kahikitea. Others were collected from a clearing in the forest. This clearing has remained undisturbed by agricultural work and is covered by silver tussock, some manuka, lichens and mosses. Other specimens were collected from the forest floor in the fringe of the forest adjoining the clearing, where beech (Nothofagus sp.) forms the dominant element of the forest.

The specimen on which this description is based is 55 mm. in length, with 105 segments, and 3·5 mm. in diameter.

The prostomium is tanylobous. The clitellum is buff in colour and surrounds segments xiii to xvii. There are eight chaetae per segment, arranged in pairs. On xxiv:

ab = 0·5 mm.; cd = 1 mm.; aa = 1·5 mm.; bc = 1·5 mm.; dd = 4 mm.

There are five pairs of spermathecal pores at 4/5, 5/6, 6/7, 7/8 and 8/9 in line with ab. There is a pair of female pores on xiv, each

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pore slightly anterior to a. A pair of male pores is situated on the extreme anterior margin of xviii in line with a. No prostatic pores are visible externally. Nephridiopores commence on ii and are present in a single series on each side.

Internal Anatomy (Plate 114, fig. 2)

There are no specially thickened septa.

Alimentary Canal. A rounded muscular pharynx occupies the first four segments. A strong walled muscular gizzard lies in vi. The pharynx and the gizzard are joined by a wide, thin-walled pro-ventriculus in v. The oesophagus extends from vii to xv and lacks oesophageal glands. The intestine commences in xvi. It is wide and very thin-walled and has a typhlosole.

Vascular System. The dorsal blood vessel is unpaired throughout its length. There are four pairs of hearts in segments x, xi, xii and xiii.

Reproductive System. There are two pairs of free polylobate testes in × and xi, and a single pair of polylobate ovaries in xiii. There are five pairs of spermathecae, in segments v, vi, vii, viii and ix. The spermathecae are bilobed in form (Plate 114, fig. 3), and it is difficult to decide whether either lobe may be regarded as a diverticulum of the other. The inner (medial) lobe is a thin-walled sac lying almost on the ventral aspect of the peritoneum and is joined to the outer (lateral) lobe close to the body-wall by a very thin-walled duct. The outer lobe, however, consists of a thick-walled sac which opens to the exterior via a distinct muscular atrium. It seems very likely that this outer thick-walled sac with its muscular atrium constitutes the sperma-theeal sac and that the inner thin-walled sac is the diverticulum. There is a single pair of prostates. Each prostate opens by a narrow duct in xvii and follows a convoluted course from xvii back to xxiii, where it terminates. There is a small sac containing penial chaetae beside the prostate in xvii. There are three pairs of diffuse vesiculae seminales in x. xi and xii. Those of x are much smaller than those of xi and xii.

Small coiled nephridia commence in ii and there is a pair in every segment posterior to ii.

In its general external features this species mostly closely resembles R. besti and R. edulis, described by Benham in 1904. The possession of five pairs of spermathecae, however, serves to distinguish this species from any other.

References

Beddard, F. E., 1889. Proc. Zool. Soc., London. 1889: 380.

—— 1892. Some Further Notes on New Zealand Earthworms, with Observations on the Known Aquatic Species. Quart. Journ. Micr. Sci., 30.

Benham, W. B., 1900. On Some Earthworms from the Islands Around New Zealand. Trans. N.Z. Inst., 33, 122.

—— 1904. Earthworms from the Kermadecs. Trans. N.Z. Inst., 37, 289.

—— 1904a. On Some Edible and Other New Species of Earthworms from the North Island of New Zealand. Proc. Zool. Soc., London, 1904 (2), 220.

—— 1905. An Account of Some Earthworms from Little Barrier Island. Trans. N.Z. Inst., 38, 248.

—— 1905a. Some Additional Notes on the Earthworms of the North Island of New Zealand. Trans. N.Z. Inst., 38, 239.

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Benham, W. B., 1909. Report on the Oligochaeta of the Subantarctic Islands of New Zealand, in Subantarctic Islands of New Zealand. Wellington.

—— and Cameron, Gladys, 1913. The Nephridia of Plagiochaeta (Perieodrilus) ricardi and of P. montanus. Trans. N.Z. Inst., 45, 191.

Michaelsen, W., 1900. Das Tierreich—10, Oligochaeta. Berlin.

—— 1905. Die Oligochaeten der deutschen Sudpolar-expedition 1901–3. ix, Zoologie, 1.

—— 1907. Oligochaeta, in Die Fauna Sudwest-Australiens, 1. Jena, 1907.

—— 1923. Oligochaten von Neuseeland und den Auckland-Campbell Inseln, nebst einigen anderen Pacifischen Formen. Dr. Th. Mortensen's Pacific Expedition, 1914–16, no. 17.

Pickford, Miss G. E., 1937. A Monograph of the Acanthodriline Earthworms of South Africa. W. Heffer & Sons Ltd., Cambridge, England, 1937.

Stephenson, J., 1930. The Oligochaeta. Oxford, Clarendon Press, 1930.