The Octopodous Mollusca of New Zealand.
I.—The Midget Octopus of the Coastal Waters.
[Read before the Otago Branch, June 9, 1942; received by the Editor, June 24, 1942; issued separately, December, 1942.]
The following species of Octopus have been recorded from the coastal waters around New Zealand:—
O. maorum Hutton, 1880.
O. communis Park, 1883.
O. australis Hoyle, 1886.
Pinnoctopus cordiformis Quoy and Gaimard, 1833.
The diagnoses of these species, with the exception of O. australis, are given in Suter's Manual of Mollusca, 1913, and are copied from the original accounts. Suter added nothing to our knowledge of this group from his own observations, and these earlier diagnoses are very superficial and insufficient to enable one to be certain of the animals to which they respectively refer.
The more recent method of distinguishing species of this enormous genus, so widely distributed in all oceans, is that of Robson (1929), in his Monograph, published by the British Museum and covering about 100 species.
In the determination and description of species at the present time it is no longer sufficient to give in general terms the shape and size of the body, its colour and ornamentation and the relative length of the arms, etc., as was done by the earlier zoologists. It is now necessary, if we are to follow Robson, as we must, to make about a dozen accurate measurements of each individual and reduce these to a percentage of the length of some standard, such as the length of the mantle—quite a laborious and tedious proceeding involving some twenty mathematical calculations for each individual: multiply this by 23, and it is seen that one is justified by using the word “laborious.” Then with about two dozen individuals one has to obtain the range and the average of each of these measured items, or “indices” (as Robson terms them) in order that one may compare them with those for allied species as detailed in his Monograph. I give later in this article the facts in tabular form.
With regard to New Zealand species enumerated above, Robson (1928) gives a detailed account of the external and some internal features of two male individuals of O. maorum in that collection, and in his Monograph suggests that O. communis is probably a synonym of that species which is the type of a new sub-genus Macroctopus. Unfortunately, the type of Park's species was lost when the Nelson Museum, in which it was housed, was destroyed by fire.
As to “Pinnoctopus,” Robson (1929, p. 185) suggests, since no one has described it since Quoy and Gaimard, that it was probably a specimen of O. maorum “having adventitious lateral folds of the skin.”
These New Zealand species vary in size from the “Giant” (O. maorum) whose total length may be as much as 5 feet 8 inches and its body alone about 10 inches (Robson) down to the “Midget” (O. australis) whose body does not exceed an inch and a half in length, and its total length a mere three to four inches.
In this present article I concern myself with this well defined, small littoral octopod originally described by Hoyle in the Challenger Reports from Port Jackson, N.S.W., namely, Octopus australis.
In his Monograph, Robson, in a footnote on p. 145, transfers this species to a new genus Joubinia, which he characterises (p. 187) in the following terms:—
“Octopods with the web equally developed in all its sectors and but little continued up the arms. The adlateral tooth of the radula is bicuspid (?). The penis has a second diverticle and a long primary diverticle (like Enteroctopus). The ligule of the hectocotylus resembles that of Bathypolypus, having markedly inrolled sides and wide cheeks.”
He emphasises the last two points as being different from those in the genus Octopus, sensu latu. But in 1938 Adam points out that this title Joubinia has been used by Bürger for another animal and suggests in its place the name Robsonella for the octopod.
Hence the synonymy of this small creature is:—
Genus Robsonella Adam, 1938.
Joubinia Robson, 1929.
Robsonella australis (Hoyle, 1885).
Octopus australis Hoyle.
Polypus campbelli Smith, 1902.
Polypus australis Massy, 1916, and Berry, 1918.
Of this small species I have examined 23 individuals, of which 5 are males and 16 females, some of which I have dissected, so that I am able to add something to the facts recorded by previous zoologists, none of whom appear to have studied the internal anatomy.*
I am able thus to extend our knowledge, for during my curator-ship of the Otago University Museum I preserved all animals that were brought in to me, whether common or rare, known or unknown specifically, in the hope and expectation that at some future time zoologists may wish to study the groups to which they belong.
In my ignorance I supposed that these little octopods, as well as some other rather larger ones, were the young of the large O. maorum and they were registered under that name, for I had not time always to examine the animals as they came in (for I was also Professor of Biology), and all one could do was to record locality and donor.
But one day a small specimen about two inches in length was received accompanied by the eggs laid by her. This opened my eyes to the fact that these small littoral octopods might be mature and consequently belonged to a species distinct from O. maorum.
Distribution of the species as recorded by Robson:—Port Jackson, 5–15 fathoms; Hoyle. Spirits Bay, North Island, New Zealand,
[Footnote] * After completing the manuscript of this account seven more specimens of the species were obtained in or near the entrance to the Otago Harbour.
11–20 fathoms; Massy. Gray's Beach, New South Wales; Brazier. Off Gabo Island, Victoria; Berry.
My own collection includes additional localities off the coasts of New Zealand:—Hawke's Bay.* Portland Island, off the Mahia Peninsula, East Coast, North Island. Tasman Bay, 10–30 fathoms, Nelson. Foveaux Strait, 17 fathoms. Otago Harbour. Stewart Island; shore.
It is thus distributed along the whole of our coasts from the extreme north, Spirits Bay, to the extreme south, Stewart Island; on both the East and West Coasts.
The number of individuals and the sex:—
|Reference Letter.||Museum Register or ad hoc number.||Number of Individuals.||Sex.||Locality.|
|A||A.′28.24||6||3 m. 3 f.||Portobello, Otago H.|
|B||1931||3||3 f.†||Otago Harbour.|
|C||22||2||1 m. 1 f.†||Stewart Island.|
|D||A.′15.34||1||1 f. with eggs.||Oyster beds, Foveaux Strait.|
|E||A.′29.111||4||1 m. 3 f.||Oyster Beds, Foveaux Strait.|
|F||(—–)||3||3 f.†||Portland Island.|
|G||Coll. G. M. Thomson||2||2 f.||Tasman Bay, between Nelson and Stephen Is, 10–20 fathoms.|
|H||(—–)||2||2 f.||Hawkes Bay.|
General Account of External Features. (Fig. 1.)
Robsonella australis is a littoral or shallow-water species of small size, measuring usually about one inch in length and three-quarters of an inch in breadth. Details of actual measurements are given later. (See p. 235.). The nearly spherical body is on its dorsal surface beset with closely-arranged, small, rounded papillae, which may be continued over the head on to the dorsal arms and web (or “umbrella” of some authors). The colour is a pale to darker brown, uniform in tone and is usually paler ventrally, where the skin is smooth. There are no special markings, though in some of the individuals there are a few darker spots along the dorsal arms.
The eyes are somewhat prominent, but this seems to vary according to the condition of preservation. In most cases a small and inconspicuous supra-ocular cirrus is evident, though it is absent in others. The arms are approximately of equal length, though the two dorsals are slightly shorter and the dorso-laterals slightly longer, when measured in millimeters. They are 2 ½ to 3 times as long as the body.
In none of the 23 specimens are any of the suckers suddenly enlarged as Smith describes and figures for O. campbelli (p. 202,
[Footnote] * I owe thanks to Dr Oliver, Director of the Dominion Museum, for allowing me to examine these.
[Footnote] † Some of the above are very small, viz. those of B; one f. of C; two of E. These are about ½ inch or less in diameter.
[Footnote] As these are at the time of writing still stored in the Museum, these reference letters and registration numbers will allow any further zoologist to compare them and to recognize the individuals referred to in this account. I have also deposited with the Director the results of the measurements of the specimens.
pl. XXIV, figs. 9, 11). As no later author has referred to these enlarged suckers, one must regard them as being an abnormality, and not, as Smith suggested, an indication of the male sex. This they certainly are not. There is no difference in size of body, nor in other external features between male and female: other than the presence of the “hectocotylus” in the male.
The extent of the “web” or “umbrella” between the arms is approximately equal in all the inter-brachial spaces, being about one quarter to one fifth the length of the arm, though in most instances that between the pair of ventral arms is shorter than the rest.
The mantle aperture is wide, extending from the level of the eye on each side.*
The funnel or “siphon” extends usually about halfway along the ventral side of this sector of the web, though its length is somewhat variable, according to state of contraction.
An important organ amongst the external features is the Hectocotylus in the male. This spoon-shaped structure is a modification of the extremity of the third arm of the right side. In this genus this has a very characteristic form (fig. 5). The short, oval, spoon-shaped “ligula” with well-rounded, inturned and thick lateral lips overhanging the groove, which is deep and broad; there are no transverse laminae or ridges across the floor, such as occur in some species of Octopus. Projecting into this space is the “calamus,” short and pointed, indeed tongue-shaped and traversed by a groove in continuation with the seminal groove along the side of the arm, formed by the narrow extension of the web of the arm.
The hectocotylus in the present series agrees more closely with that figured for campbelli (Robson, p. 190) than with his figure for australis on p. 145, in which the lips of the ligule are relatively much thicker and apparently overlapping the groove more than in those examined by me. But this seems to be a result of greater contraction.
The above is a general account which will enable anyone to recognise this little octopod, but some remarks must be made as to any variation from these statements.
Shape of Body.
Although many of our specimens are globular, others tend to be oval; in some, the greatest diameter of the body is near the anterior end, in others near the hinder end. In some the hinder end is more or less pointed. (Fig. 3.) For example, in the two specimens from Tasman Bay (G) one is “bursiform” or globular, the other a narrower oval and somewhat pointed posteriorly.†
In two individuals from Stewart Island a similar variation occurs; and I have found like differences in shape in several other localities. So that Robson is justified in his remark (p. 25): “It is evident that the shape of the mantle (i.e. “body”) can only be used
[Footnote] * By what is evidently a slip of the pen, Robson in his description of this species, on p. 144, writes that “the mantle aperture is narrow (C),” but on p. 26 he defines (C) as “wide,” and Hoyle (p. 88) says it extends “nearly halfway round the body”: and so it is shown in Smith's figure 8, pl. XXIV.
[Footnote] † The outlines were taken by running a scalpel round the body, incising the underlying card, and then pencilling this mark.
Outlines of five individuals to show variations of form of body (n.s.). The letters refer to the list of specimens on p. 228.
A—The more usual or typical form.
D—The female which laid the eggs.
for the discrimination of species with very great caution.” The colour likewise is somewhat variable, depending to some degree on the liquid used for preservation; thus in those preserved in formaline the brown has a pinkish tint, which is quite absent from those in alcohol; formaline is preferable to alcohol as a preservative for these octopods, especially for the study of the internal anatomy. I note that in those from Portland Island the basic colour is “marbled purplish and pale brown.”
In some individuals there are in addition to the uniform round papillae of the dorsum a few somewhat longer conical tubercles scattered amongst them: as in those from Portland Island and some of those from Portobello (Otago Harbour).
In Hoyle's type there is figured a pair of ventro-lateral ridges on the ventral side of the mantle (1856, Fig. 5). No other author has
Fig. 4—Outline of an egg with embryo (camera lucida × 15). b. body; h. head; m. mantle flap with funnel; st. stalk by which the egg shell is attached to others; y. yolk sac. Fig. 5—Hectocotylus (× 4) s.g. seminal groove along the arm. Fig. 6—A spermatophore from Needham's sac (× 5). a.b. aboral pole; gr. granular mass at ruptured region; or. oral pole; pr. projectile tube; sp. sperm tube. Fig. 7—Oral end of spermatophore with part of the projectile apparatus (pr) consisting of a closely coiled spiral thread or cap which will be forced off to release the spermatozoa when the affair reaches the female apparatus. Fig. 8—The “Packet” partially dissected out showing chamber-like dilatations of the distal regions of the ducts (k, m, n, p). Fig. 9—The interior of the mantle chamber seen by removal of the mantle flap; f. funnel; fl. funnel lock, the index line should reach the trans. ridge; fp. adsiphonal pouch; fp.1. thickened region of its wall; g. gill; m. cut edge of mantle flap; o.p. oviducal pore; ov. ovarian sac; r. renal sac; rp. renal pore; s. septum; tr. thickened ridge on mantle edge. Fig 10—Female reproductive apparatus (× 4). a.b. the two chambers of the spermoviducal gland; c. enlarged commencement of the vagina; od. oviduct; op. external pore; ov. ovarian sac; v. vagina. Fig. 11—Male apparatus of a mature individual, unravelled and displayed (enlarged); acc. accessory gland; app. appendix; d.1. chief diverticulum; d.2. the characteristic second diverticle; N. Needham's sac; k. anterior chamber of Needham's sac; m.m. parts of the appendix; n. enlargement of sph.; p. distal enlargement of accessory gland; pe. penis; p.d. penial duct (or distal vas deferens); spg. spermatophoral gland; T. testicular sac; vdp. proximal vas deferens (or vas efferens). Fig. 12—The male apparatus of an immature individual (× 6). The appendix is much simpler. Fig. 13—The aboral end of a spermatophore (much enlarged). sp. masses of spermatozoa arranged in a spiral. Fig. 14—The penis and chief diverticulum opened to show the contained spermatophore of a mature individual (much enlarged).
observed these, and even Hoyle suggests “possibly it is due to differing modes of preservation or to varying conditions of contraction.” In none of the 23 individuals in my collection is there any trace of a ridge. But in some there is a shallow, more or less evident furrow in the median line of the ventral surface, which is due to the degree of contraction of the septal muscle which is attached to the inner surface of the mantle forming the septum between the right and left pallial chambers.
Mantle Chamber. (Fig. 9.)
The funnel of most species of Octopus presents on its dorsal lining a W-shaped glandular ridge, known as the “funnel organ.” I have seen no clear evidence of its form in this species. The adjacent adsiphonal pouches,” one on each side of the base of the funnel, open posteriorly into the pallial chamber behind the “funnel lock.”
I have not been able to find a clear statement as to the function of these pouches; Naef is not very expressive in the matter. Do they not assist the flaps of the “lock” in closing the mantle aperture during respiration or locomotion? The compression of the wall of the pallial chamber forces the water forwards during locomotion; it will therefore enter the pouches and distend them, and the flaps of the “lock,” which are actually the produced walls of the pouches, will be forced against the thickened edge of the mantle, and thus close the exit, allowing the water to escape only through the funnel.
The “funnel lock” consists of a pair of semicircular flaps separated by a slight notch in the middle line, but the thickened edge of these flaps is continuous over this notch.
The gill contains 6 or 7 or 8 lamellae.
The pallial septum, which separates the mantle cavity into right and left chambers, is perforated by an interpallial aperture, which in most instances is extensive, that is, it is as long as that part of the septum in front of it, or even longer. But in one of the individuals from Portobello (B) it is very small, quite far back near the posterior end of the septum.
Into the mantle chamber the genital and excretory ducts open. In the female the genital pore is paired as in all Octopods; so is the excretory pore. In this species the female pore is deep down in the chamber at the base of the gill, outside of and dorsal to the renal aperture. Whereas in the Octopus vulgaris and some other species this genital pore lies far forwards, alongside the anus.
Little appears to be known of the internal organs such as the alimentary tract and the reproductive apparatus, either for this species or for the genus itself. I have dissected three or four specimens in spite of the small size.
The alimentary system does not present any particularly diagnostic modifications on that of the well-known O. vulgaris. But the reproductive system both of the male and the female differs more or less extensively from those that are figured in such literature as I have been able to consult, viz., Marchand and Robson and Naef. However, I have been able to study Marchand's classic article on the male system (1907) and will follow his nomenclature.
The Female Apparatus, (Fig. 10.)
From the ovary or, more correctly, the “ovarian sac” at the posterior end of the body, the two slender oviducts arise from a short, wide, thin-walled, common “antrum” lying near the anterior limit of this ovarian sac. In one individual the ovarian sac occupies the greater part of the visceral cavity, extending from the posterior wall forwards nearly to the oviducal pore, from which it is separated by a portion of the renal sac; further, it extends from the mid-line to the lateral wall of the body. The oviduct passes obliquely forwards and outwards to a subspherical swelling, the “oviducal gland,” or as Robson terms it (1929), the “spermoviducal gland,” for he quotes (p. 138) an observation made by Racovitza in 1894 that separmatozoa were found therein. The “spermoviducal” gland consists in this species of two chambers in sequence, (a) a thick-walled, pale-coloured hemispherical chamber receiving the oviduct, and (b) a thin, translucent-walled chamber appearing dark owing to the character of its contents. This opens by a communication near the posterior end of the junction into a hemispherical, thick-walled, pale-coloured sac, (c) which leads into the long tubular vagina; this turns abruptly forwards to reach the oviducal pore lying close to the base of the gill, immediately anterior to the renal papilla.
So far as literature enables me to form a judgment, the vagina is a good deal more massive than in most species.
By a fortunate chance the female from Foveaux Strait (specimen D) was accompanied by her eggs, captured in the same haul; they were deposited on the inner surface of the flat shell of an oyster. (Fig. 2.) The eggs are laid in groups of bunches, each bunch being independently attached to the shell by an axial thread to which the individual eggs are in their turn connected. About two dozen such bunches lie in this shell; each of which measures about 15 mm. in length, though larger bunches are also present; such a bunch contains about 60–70 eggs.
Each egg measures 2·5 mm. in length by 1 mm. in width; it is a much elongated oval, attached to the axial thread by a short stalk. Mounted in glycerine and studied after the temporary shrinking of the envelope has resumed its normal condition, it was drawn under camera lucida with a Zeiss number 2 objective and ocular 1. The figure therefore was 30 times natural size, but it is here reduced to half this. (Fig. 4.) The embryo had developed till the body, head and arms are differentiated. I was unable to make out the eye with certainty, as the rounded bulge seems almost equally prominent on each side, or rather on the dorsal and the ventral aspect as the body lies.
I have the eggs of another species which attain a greater size than this.
The Male Apparatus. (Fig. 11.)
The dissection of a mature individual from Stewart Island (C) exhibited the apparatus in its usual complexity, though in some respects it is more complicated than that normally described. The penis, which is 10 mm. in length, has the characters which Robson
found to be diagnostic of his genus Joubinia, that is Robsonella of Adam; it has in addition to the “chief” diverticulum, which is the upturned portion of the J-shaped structure, a small globular accessory diverticulum.* From the bottom of the loop formed between the penis and its diverticulum the “penial duct” or extreme anterior or “distal” portion of the “vas deferens” arises; this after a short course plunges into the anterior of a conspicuous oviform mass, about 7 mm. in height, which lies to the left of the penis. This is the “packet” of Marchand and contains or is formed by a series of chambers and tubes closely wrapped together; each is surrounded by its layer of connective tissue, and the whole bound by connective tissue. (Fig. 8). It will be appreciated by fellow anatomists that the unravelling of this small complex was a tedious and time-taking job. Oh! happy naturalists! whose concern is with such animals as Lepidoptera, or fishes or gastropod shells, where it is sufficient to study externals, either the colour pattern of the moth, or the number of scales and fin rays of the fish in order to ascertain the species.
This is not meant as a disparagement of such naturalists. Far from it; we recognise that their work has in the past as in the present been of immense service to the anatomist. The work of those enthusiasts laid the foundation for much of our knowledge to-day and is still necessary.
We anatomists have to take cognisance of the internal structure, which involves time and labour; but it is likewise an exciting business, tracing out these hidden organs, not knowing what the successive results may show. It is like exploring in some unknown country. And this particular job, requiring even more patience than the study of the anatomy of an earthworm, in that the connective tissue had to be carefully picked away, bit by bit so as to avoid injury to any one of the concealed organs; I made sketches of the outcome of each successive exposure of unravelling and displacement of the parts so as to find the relation of each to the other. The result is shown in the figure 11, which is somewhat simplified and rearranged.
It will be convenient to follow Marchand's plan of tracing the “vas deferens” from the testis. This organ lies as usual in the Octopods at the posterior apex of the body, enclosed, of course, in the “testicular sac.” From this arises the “proximal vas deferens” (or “vas efferens” of earlier writers). This passes forwards as a delicate, much undulating canal amongst the coils of a wider tube, the “spermatophoral gland” (or as it was formerly called, the “seminal vesicle”). Into this long, coiling, glandular tube the “proximal vas deferens” enters.
This “spermatophoral gland” makes a long, double U-shaped course extending from the testis forwards. Its anterior, ultimate limb bends abruptly towards the animal's right side (it is displaced in the figure for convenience), and here the character of its wall changes, becoming a thin-walled, transversely disposed enlargement or “saccule” as I term it (n). From the wall of this “saccule”
[Footnote] * In a mature individual dissected later this secondary diverticulum is lacking, and the primary is very long, almost the length of the penis. Its rounded tip occupies the position of this secondary diverticulum, but there is no internal subdivision.
a short, slender duct opens into the first of a series of chambers (p), which is merely a swelling at the anterior end of the “accessory gland” (or “prostate” of authors).
The accessory gland, as Marchand terms it, is a long tubular sac of irregular diameter, of a pale orange colour with a thick glandular wall; internally the lining is smooth, and I found no contents; it reaches back to the apex of the body, not straight, but more or less undulating; its posterior end is very abruptly recurved and slightly enlarged. The length of this gland where extended is 30 mm.
Returning to the complex of chambers that constitutes the “packet”, from the enlargement of the accessory gland (marked p) there passes forwards a chamber with indented wall, thick and glandular in appearance (m) which curves round to the right side, bends abruptly on itself, loses its glandular character and, coursing close to and parallel with a chamber (k), enters an enlargement at the anterior end of “Needham's sac.”
This complex of chambers m and n corresponds to the structure which Marchand terms the “appendix” of the accessory gland or “rangier druse.”
Needham's sac has the usual form and disposition in the body; a long, cylindrical tube, about 15 mm. in length in this specimen: of a pale orange colour. It contained spermatophores. At the anterior end it widens out to form an enlargement into which the end of the “appendix” opens, and from which its continuation forms a somewhat oviform chamber (k) in which were two complete spermatophores, each lying in its own groove along the lining of this chamber, which is thrown into numerous folds.
This chamber (k) suddenly decreases in size and gives outlet to the “penial duct” or “distal vas deferens,” and so we reach the penis.
The penis also contained a spermatophore (fig. 14), the “projectile tube” being coiled up in the diverticulum (as described by Marchand, p. 327, and figured).
A comparison of this system with the figures given by Marchand and by Robson show certain very evident differences from all other species.
The “appendix” or blind sac through which the accessory gland communicates with “Needham's sac” is enormously developed, and, in place of its simplicity in other forms, is here subdivided into two distinct regions or differentiations, namely (m) a thin-walled, sacculated chamber and (m′) a thick-walled, glandular, more or less cylindrical chamber which opens by a narrow duct into the upper part of Needham's sac.
And it is not only in this individual that this complexity occurs. I find it also in an immature male from Portobello, though the appendix is there less complex. (Fig. 12.)
Spermatophore. It may be desirable to give a brief account of this so remarkable structure, though this account is but imperfect in details. (Figs. 6, 7, 13.) One that was removed from Needham's sac has a length of 40 mm. The enclosed chamber within the thinnish cuticle is divisible into two regions. A broader chamber or “tube”
(sp) containing a loose, spirally-coiled mass of spermatozoa, enclosed in the thin horny-brown envelope; and (pr) a longer, narrower tube with thicker and double envelope in which is the “projectile apparatus,” of a closely-coiled spring. In the figures of this astonishingly complex apparatus I use the terms employed by Racovitza, to whom Marchand refers in the work on the male organs.
To what degree there may be specific differences is not known. However, I give a figure of what I find in R. australis.
Explanatory Note of the “Indices” as used by Robson in diagnosing the species of Octopus, and as defined on p. 38 of his Monograph.
The length of the “mantle” (or body) is taken from the apex to the middle of the line joining the eyes.
The width of the mantle as a percentage of its length.
Interocular breadth, i.e., “the distance between the outer-most point of the eyes” as a percentage of the mantle length.*
Length of the longest arm as a percentage of the total length, i.e., length of the body plus that of longest arm.
Diameter of largest sucker as a percentage of the mantle length.
The web depth; that is the depth of the deepest sector as a percentage of the longest arm (apparently the longest arm of the whole series of specimens, as he only gives one figure).
The length of the ligula of the hectocotylus as a percentage of this arm.
It will be seen, therefore, that the determination of species depends on mathematics—a tedious procedure. He also includes the “arm formula” and “web formula,” of which he remarks on their comparative unimportance.
Range and Average of the Indices for sixteen specimens of Robsonella australis:—
For comparison with these I quote the corresponding numbers given by Robson for the six specimens studied by him:—
The indices for “campelli” fall within the range except that for G, that is the diameter of the sucker, which is 21, for this individual had abnormally large suckers on one arm.
[Footnote] * If a tyro may criticise these terms, one would prefer “supra ocular” width as being more accurate; and “body” rather than mantle, since the latter word is usually used for the “mantle flap” which encloses the mantle or pallial chamber.
[Footnote] † This high figure of 100 is found only in three very small individuals; and excluding these the average is 74.
Adam, 1938. Zoolog. Anzieger, p. 223.
Berry, Stillman, 1918. Cephalopoda. Biological Results of Fishing Experiments of F.I.S. Endeavour, 1909–14. Sydney.
Hoyle, W. E., 1886. Cephalopoda. Report of the Scientific Results of the Voyage of the H.M.S. Challenger during the years 1872–76. Zoology, vol. XVI, p. 88, pl. iii, figs. 4, 5.
Hutton, F. W., 1880. Manual of New Zealand Mollusca. Wellington.
Marchand, W., 1907. Studien ub. Cephalopoden. I.” Zeit. f. Wiss. Zool., vol. 86, p. 311.
Massy, Anne L., 1916. Cephalopoda. British Antarctic (Terra Nova) Expedition, 1910. Zoology, vol. ii, pp. 141–176.
Naef, A., 1923. Die Cephalopoden., Monogr. 35, in Fauna u. Flora d. Golfo di Napoli.
Park, James, 1885. Description of a New Octopus. Trans. N.Z. Inst., vol. XVII, p. 198.
Parker, T. Jeffery, 1885. The Size and External Sexual Characters of O. maorum. Nature, vol. XXXI, p. 586.
Robson, G. C., 1928. The Giant Octopus of New Zealand. Proc. Zool. Soc., p. 257, figs. 1–6.
—– 1929. Monograph of Recent Cephalopoda. British Museum, Natural History, vol. I.
—– 1932. Ditto, vol. II.
Smith, E. A., 1902. Mollusca. Southern Cross Expedition (British Museum), p. 201.
Suter, H., 1913. Manual of New Zealand Mollusca. Wellington.