Further Notes on New Zealand Chitons (Polyplacophora).
[Communicated by Albert E. Brookes; received by Editor, December, 1929; issued separately, 29th August, 1929.]
This paper describes, in the first place, a very fine addition to the Chiton fauna of the Dominion sent to me by Mr. A. E. Brookes. It is a new and large Notoplax, in which the girdle is densely clothed with long, slender, white adpressed spicules; in the second place a valuable collection of New Zealand Chitons made by Dr. H. J. Finlay is described and two important additions to the fauna of the Dominion are made, both belonging to the primitive genus Lepidopleurus and one of them an entirely new and distinctive species which I have pleasure in naming after Dr. Finlay.
Notoplax (Amblyplax) brookesi n. sp. (Figs. 1, 2, 3, 4).
General appearance.—Valves reduced, girdle very broad, encroaching slightly at the sutures, anterior valve ray-ribbed, lateral area defined by a diagonal fold, dorsal area strongly raised and longitudinally lined, pleural and lateral areas equally sculptured with flat, elongate, spaced granules, coloured with mottlings varying from darkgrey to greenish-grey, thereby giving to the whole shell a greenishgrey tone. The girdle is almost unique, being densely clothed with very long, slender, adpressed white spicules, almost resembling long white hairs.
Anterior valve.—Five ray-ribs which are barely raised, but defined by large, flat, elongate, ovate granules, the whole valve is decorated with large, flat, ovate to subacute granules, commencing minute at the apex and increasing in size towards the girdle.
Median valve.—Dorsal area beaked, raised, whitish with longitudinal lining but only longitudinally grooved near the beak; this area is closely transversely grooved and in addition is irregularly crossed by several broad growth-grooves; pleural area is evenly decorated with large, elongate, subacute flat grains; these increase in size anteriorly, and towards the girdle; the lateral area is indicated by a diagonal fold, the posterior margin is recurved slightly at the girdle, sculpture is similar to that of the plcural area except that the granules are larger.
Tail valve.—Mucro posterior of central, slope immediately behind mucro very steep, from there to the posterior margin concave, the broadly wedge-shaped portion immediately behind mucro is white, and the grains are large, circular and convex; the rest of this valve decorated with flat, elongate, ovate, subacute granules similar to the median valves except that the granules are here less pointed.
Articularmentum.—Inside white merging into pale bluish-green towards dorsal ridge and posterior margin, slits, anterior valve 5, median 1/1, tail 11, teeth very thick in tail valve, edge blunt, sometimes notched in the middle, shallowly grooved on the outside, the insertion-plate rather broader than is usual in this subgenus; sutural laminae in median and tail valves produced forward and broad, sinus between, medium, insertion-plate of anterior valve broad, finely grooved on outside, teeth sharp.
Girdle.—Broad, densely clothed with adpressed, long, slender, white spicules measuring, in complete example, 812 mmm. long by 37 mmm. at base tapering to 25 mmm. towards the point; hair tufts composed of white, glassy, straight spicules measuring 1320 mmm. in length by 37 mmm. to 50 mmm. at base tapering to 13 mmm. at point.
Habitat.—Tauranga Harbour, dredged 3 fms.
Comparisons.—As compared with oliveri, the insertion-plate of the anterior valve is double the width, the insertion-plate of the tail valve is broader and more dentate. It is easily distinguished from oliveri, mariae, and the two subspecies of this latter, stewartiana and haurakiensis, by the absence of the “comma-like” grooving of the dorsal area, and the spiculose girdle-clothing, from rubiginosus and foveauxensis by the sculpture consisting of flat instead of convex grains and the long, slender spicules of the girdle-clothing. This form is nearer Notoplax s.s. than any other known member of this subgenus.
Notoplax (Amblyplax) rubiginosus Hutton, 1872.
(Tonicea rubiginosus Hut. Trans. N.Z. Inst. 4, 1872, p. 180; Notoplax (Amblyplax) rubiginosus of Ashby, Proc. Mal. Soc. (Lond.), vol. 17, pt. 1, pp. 22-3, 1926).
In the Finlay collection was one complete shell, and one median valve, both dredged in 60 fms. off Otago Heads. In identifying these examples with N. (A.) rubiginosus Hutton, it has not been possible to compare them with the holotype, but only with a very juvenile example that was associated with this species; the identification is based on the elongate convex granules of the sculpture, in some respects they do not quite accord with the holotype. Up to the present this species has been extremely rare, N. (A.) foveauxensis Ashby has by all writers been mistaken for rubiginosus Hutton.
Lepidopleurus inquinatus Reeve, 1847.
(Chiton inquinatus Reeve, Conch. Icon. t. 23, f. 154, 1847).
In the collection are seven small specimens and separate valves dredged in 3 fms., Dunedin Harbour, and a series of small examples and separate valves dredged in 60 fms., Otago Heads; all seem typical except one small example that shows carination.
Lepidopleurus columnarius Hedley and May, 1908. (Fig. 9).
(L. columnarius H. and May, Rec. Aust. Mus., vol. 7, No. 2, 1908, p. 123, Pl. 24, Figs. 27-8).
This is a very interesting addition to the New Zealand fauna, it being a rare northern Tasmanian species only known from dredged specimens.
In the collection is one rather worn median valve, but the sculpture is sufficient, coupled with the peculiar shape of the valve, to make identification assured. The angle of divergence is about 45°, exactly the same as is a median valve in my own collection which was dredged off the Schouten Islands, Tasmania, in 80 fms. The example in the Finlay collection was dredged in 95 fms. off the Auckland Islands.
Lepidopleurus finlayi n. sp. (Figs. 5, 6, 7).
General appearance.—Elliptical, carinated, anterior valve decorated with numerous radial rows of closely-packed granules, median valves with longitudinal rows of rather coarse granules, the rows becoming widely spaced towards the girdle, the lateral areas raised, granules coarse, circular, convex, and spaced, some valves showing radial arrangement; colour pale brown, strong bunches of spicules protrude between the valves at the sutures, girdle scaly but shows a few scattered long spicules and possesses a distinct girdle-fringe.
Anterior valve.—Broad, elevated, decorated with closely-packed rows of circular, convex narrowly spaced granules; I count 45 of these rows, but as some are bifurcate, and there is irregularity in direction, this number is only approximate; this valve possesses three broad, deep, concentric growth-grooves; it also has on the posterior margin on either side three large pustules, more particularly described in the median valve.
Median valve.—Carinated, dorsal area inseparable from the pleural; these areas are decorated with longitudinal rows of circular, convex granules, which commence small and crowded at the jugum, where they are often touching, sometimes imbricating, increasing in size but mostly imbricating in the pleural area; the longitudinal rows are close together near the dorsal ridge, the trough between barely the width of the grains, but the spacing between these rows increases most abruptly to about three times the diameter of the larger grains. At the posterior margin of the valves are three to four equi-spaced protuberances standing up four times the height of the larger grains, a method of ornamentation that is almost unique in members of this genus. The lateral area is strongly raised, decorated with large, convex, spaced grains, considerably more raised and spaced than those of the pleural area, without arrangement near the dorsal ridge, but becoming radial towards the girdle; there are four broad concentric growth-grooves.
Tail valve.—Dorsal area undefined; this and pleural area are sculptured similarly to these areas in the median valves, mucro defined, slope immediately behind, very steep, gradually becoming less
until slightly concave near margin; the whole of this posterior portion of valve decorated with circular, convex grains, two or three times the size of those in the anterior portion of this valve; sutural laminae shallow, straight edged, but produced laterally.
Measurements.—The holotype when dry and curled measured 4 × 2.75 mm, and the median valve photographed measures 2.5 × .50 mm. The granules in the pleural area are 62 mmm. in diameter, the coarse pustules on the posterior margin of median valves protrude upwards of 88 mmm., the girdle scales measure 62 mmm. × 31 mmm., the short stout spicules of the girdle fringe are deeply longitudinally grooved, the few smooth long spicules that also are found scattered in the girdle fringe are 287 mmm. × 25 mmm., a broken spicule from the peculiar sutural tufts is 188 mmm. in length.
Girdle.—Before disarticulation the girdle was clothed with irregular spade-shaped scales, many of which were not imbricating but more or less erect; the normal girdle fringe consists of short stout spicules, but in places are long, slender, glassy spicules sometimes arising from the fringe, at others from the centre of the girdle; these apparently are quite smooth, whereas the fringe spicules proper are longitudinally scratched or grooved. Under 65 mag. these longer spicules appear to become easily detached and may be deciduous, leaving the animal entirely free of girdle spicules at certain seasons or under certain conditions. As I have before pointed out, girdle spicules in the Lepidopleuridae seem to have little taxonomic value. But this species possesses an almost unique feature in having bunches of spicules which spread out fan-shape between the valves at each of the sutures, not as in the genus Acanthochiton being extruded from pores from the girdle opposite the sutures. These bunches were not detached by long boiling and may be of true taxonomic value.
Habitat.—Dredged in 60 fms., Otago Heads.
In conclusion, this species is without insertion - plates in any of the valves; the foregoing description has been written under 65 mag., but with only a pocket - lens of 20 mag. the coarse, spaced, convex granules of the lateral areas, the very widely-spaced, longitudinal, granulose ribs of the pleural areas, the distinct carination of the shell, the three thumb-shaped protuberances on the posterior margin of anterior and median valves, and the remarkable tufts of long spicules at the junctions of the valves, easily separate this form from any known member of the genus Lepidopleurus. I have much pleasure in naming it after the discoverer, Dr. Finlay. A second example, without the tail valve, shows a more distinct radial arrangement of the granules in the lateral area and the longer spicules scattered throughout the girdle in the type are absent.
Callochiton platessa Gould, 1846.
(Chiton platessa Gld., Proc. Bost. Soc. N.H. 2, 1846, p. 143).
In the collection are two examples from Taieri Beach, the dorsal and pleural areas show sub-cutaneous granula marking, there being
very little surface-granulation, but in the lateral areas there is some evidence of surface-granulation under 65 mag.; the interspaces are covered with parallel scratches. Specimens from Breaker Bay, Cook Strait, in my own collection, are a little more granulose; shells from Tasmania are in extent of granulation intermediate between those from N.S.W. and those from New Zealand; examples from South Australia and Western Australia show a little divergence. Dr. Nils Hj. Odhner (in Dr. T. Mortensen's Pacific Expd., 1914–16, 19, N.Z. Moll., pp. 6, 7, 1924), described a Callochiton from Campbell Is. under the name C. mortenseni Odhner, possessing 4–5 slits in median valves, and granulation almost if not entirely absent on the surface of shell. It is not at all unlikely that the two examples under review may be referable to Odhner's shell, but without more evidence I am not prepared to consider these as deserving specific separation from C. platessa.
Callochiton empleurus Hutton, 1872. (Fig. 11).
In the collection are two median valves from the Auckland Islands measuring 6·2 mm. and 4.25 × 1.5 mm. respectively, angle of divergence of the larger example 100°.
Description.—Surface smooth with minute decussate pattern; lateral areas strongly and abruptly raised; a series of deep pits broadly ovate anteriorly and square-ended, adjoining the lateral areas, commence near the beak as mere pits, and following down the line of junction of the pleural with the lateral areas rapidly increase in size and length until they extend right across the pleural area, the ridges between these pits forming narrow, longitudinal ribs; in the smaller example there are 7 pits, in the larger 10, as compared with C. klemi; the ridges separating the pits are one-third the width of those in this latter species, and the pits themselves are much longer.
Callochiton klemi Ashby, 1926. (Fig. 12).
(C. klemi Ashby, Trans. Roy. Soc. S. Aust., vol. 1, 1926, p. 243, f. 4a, 4b).
There is no example of this species in the collection, but some years ago the Dominion Museum was good enough to send me a damaged example labelled C. empleurus Hutton from Foveaux Strait. Later, when in 1926 I was describing a new Callochiton, from a single valve from Daly Head in South Australia, I overlooked the existence of this New Zealand specimen, and omitted to compare them until after publication, or I should most certainly have made the example from the Foveaux Strait my type. The following is the description of one of the median valves of this specimen, which I am depositing with the Dominion Museum.
Description.—Median valve measures 6.5 × 3 mm., angle of divergence 90°, colour flesh-pink with lighter mottlings, surface smooth except for growth-lines and minute decussate pattern; ornamented with seven almost circular pits of which the two outer are imperfectly formed; the pits themselves are very much smaller and
the ridges between are much larger, three times the width of those in C. empleurus.
The structure of the pits is very distinct from that of C. empleurus, but whether this species is truly conspecific with the unique example from South Australia cannot be stated with certainty until further examples are forthcoming from South Australia, showing the end valves. The short circular character of the pits and the broad interspaces are common to both, but I note that the South Australian shell is more beaked, and the pits are not quite identical, so the receipt of more material may, after all, make separation possible. It must be remembered that the type of klemi is about one-fourth the actual size of the valve of the Foveaux Strait shell herein figured; the angle of divergence is the same.
Note.—Dr. Finlay has called my attention to Cattochiton sulculatus Suter (Proc. Mal. Soc., 7, 294, f. 5 in text, 1907).
I have compared Suter's description with the example under review, to which it seems nearly allied but differs in the following particulars: Suter states that the whole surface of the end valves is “dotted with small black eyes,” whereas no true eyes are present in the example under review, but in the end valves are minute, scattered pits measuring under 25 mmm., the black central dot measuring about 5 mmm.; these I take to be enlarged megalopores, sense organs common to most chitons. Suter states “central areas laterally grooved,” the pleural areas are longitudinally grooved, he may have referred to the few transverse-growth grooves in the dorsal area. Suter states “the lateral areas flatly and broadly nodulose by a few concentric furrows, more pronounced near the margins; sutures crenate.” In the example described herein as C. klemi this description does not fit, although a few concentric-growth furrows exist. Suter states of the “4 or 5 deep grooves” in the pleural area “the innermost extending only half the length” of area. In C. klemi, the groove is more truly a pit, and does not extend anything like half across the pleural area. Without comparing with Suter's type, which is not for the present available, it is impossible to reconcile the discrepancies noted above, but the example from Foveaux Strait could be listed as? C. sulculatus Suter, if so desired.
Callochiton kapitiensis Mestayer, 1926. (Fig. 10).
(C. kapitiensis Mest., Trans. N.Z. Inst., vol. 56, p. 583–587, Pl. 100, figs. 2–4, 1926).
In Dr. Finlay's collection are three small examples (one broken) of the whole shell, and a number of minute separate valves, all dredged in 60 fms. off Otago Heads. Dr. Finlay labelled these Icoplax puniceus (Couthouy M.S.) Gould, 1846. I believe this is the shell that has been known under that name from New Zealand, but it still is an open question as to whether it is conspecific with the true C. puniceus from Tierra del Fuego. Thiele made C. puniceus the type of his subgenus Icoplax, but Iredale and Hull treat Icoplax as a full genus, placing in it all the pitted or ribbed forms of Australian Callochitons, and placing C. platessa, which sometimes has pitted valves (var. fossa
Ashby), in a new genus of their making. In my opinion these gentlemen have advanced no data of sufficient taxonomic value to justify their action in either case, and therefore I prefer to continue for the present to place all these under the genus Callochiton. I had hoped before now to have had the opportunity of examining an example of the American shell C. puniceus; I think it more than likely that the two shells are not conspecific, in which case Miss Mestayer's name will probably stand.
Description in brief.—C. kapitiensis has very widely-spaced, narrow, longitudinal ribs in the pleural areas, the posterior margin of median valves dentate with coarse, widely-spaced nodules, and is without pitting. The example figured herein was given to me by Miss Mestayer and is the paratype, mentioned in her type description as a “perfect specimen,” p. 584, dredged 8–10 fms., Kapiti Island, 5th February, 1925, and measures 8·25 × 5 mm. I have selected this example for figuring because of its larger size.
Eudoxochiton nobilis Gray, 1843.
In the Finlay collection is one example from Oamaru, taken on the Cape a little past the Breakwater. The specimen is preserved by the gelatine process; shell rich reddish horn-colour, smooth, girdle leathery, with isolated, spaced, horn-coloured spicules rising out of tubercles scattered over the girdle. Near the outer margin of the girdle are clumps of short, curved spicules, but only in places do these seem to approach any system of arrangement.
Ischnochiton campbelli Filhol, 1880.
(Lepidopleurus campbelli Filhol, Comp. Rend. 91, p. 1095, 1880).
In the collection are a number of excellent specimens, taken under stones at low tide at the Bluff.
Onithochiton neglectus Rochebrune, 1880–1.
(O. neglectus Roch., Bull. Soc. Philom. Paris, 1880–1, p. 120).
In the collection was a smooth variety without granulation and in which the “eyes” are difficult to discern; it was taken under kelp roots and recorded by Finlay (Trans. N.Z. Inst. 55, p. 521, 1924).