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Volume 56, 1926
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New Zealand Mollusca: No. 3.

[Read before the Wellington Philosophical Society, 22nd October, 1924; received by Editor, 31st December, 1924, issued separately, 5th May, 1926.]

Plates 100,101.

The specimens dealt with are in the Dominion Museum collection. Two of them, Plaxiphora zigzag (Hutton) and Plaxiphora ovata (Hutton), though described in 1872, had never been adequately figured. Another old specimen is Callochiton kapitiensis n. sp., which had been identified by Hutton as Chiton sulcatus Quoy, and by Suter as Chiton limans Sykes; but Mr. Edwin Ashby, to whom the broken paratype was sent, said it was an undescribed Callochiton. I gratefully acknowledge Mr. Ashby's kindness and help in identifying this and other species. Thanks are also due to Mr. W. R. B. Oliver for generous help and for his notes on the radulae of Callochiton empleurus (Hutton), Macandrellus oliveri n. sp., and Lorica haurakiensis Mestayer. Though I include figures of the radulae of these and of Acanthochiton foveauxensis and the var. kirki, I have not attempted to describe them; the slides, however, are in the Dominion Museum. I am much indebted to Miss J. K. Allan for the care she has bestowed on the drawings.

Callochiton empleurus (Hutton). (Plate 100, fig. 1.)

The radula of this species has, I believe, never been figured. I am indebted to Mr. W. R. B. Oliver for this note: “Median tooth narrowing distally, outer centrals with broad cusps. Laterals with a large black cusp ending in three strong points, the central one rounded, the outer ones sharp, pointed. Nine marginals with long cusps pointing inwards, outer pavement-like, the outer row the largest.”

Callochiton kapitiensis n. sp. (Plate 100, figs. 2–4.)

Chiton sulcatus Quoy, Trans. N.Z. Inst., vol. 4, p. 178, 1872. Chiton limans Sykes: Suter, Proc. Malac. Soc., vol. 2, p. 197.

Shell small, narrow-oval, side slopes very slightly convex, jugum acute, mucro median,

Colour.—Shell whitish-brown, mantle reddish-brown.

Sculpture.—The head-valve, lateral areas, jugal area, and posterior two-thirds of tail-valve closely covered with very minute granules, clearly defined only under a strong hand-lens. Two concentric growth-lines clearly marked on all valves. Posterior margins of valves 1–7 finely denticulate. Under lens two other growth-lines can be seen on head-valve. Median valves—lateral areas strongly marked, pleural areas with 8 very narrow raised longitudinal ridges, interstices about three or four times width of ridges. Posterior margins straight. Valves 6 and 7 of holotype badly broken on right side. Tail-valve—pleural areas ridged, mucro small, nearly central, posterior portion slightly concave. Girdle narrow, densely covered with small pillar-like scales (Plate 100, fig. 4), in mottlings of reddish-brown and white.

Length, 9 mm.; breadth, 5 mm.

Locality.—Kapiti Island, Cook Strait.

Holotype and one perfect and one imperfect paratype in Dominion Museum.

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Remarks.—The disarticulate remains of a paratype show that the insertion plates are narrow, head-valve with 15 or 16 very shallow slits, median valves 1 slit, and the interior bluish-white. A single imperfect valve in my collection, from Lyall Bay, is pink and white exteriorly, with the interior jugal area rosy pink

Suter's (5) inclusion of Chiton limans Sykes in the New Zealand fauna appears to have been based on the specimens in the Dominion Museum; but his description does not at all fit these specimens from Kapiti Island, it being apparently Carpenter's MS. description—Pilsbry (7). In the Proc. Malac. Soc. (6), Chiton limans is used by Sykes for a Port Phillip shell so named in MS. by Carpenter. This being so, and the New Zealand shell being radically different from C. limans Sykes, an Australian shell, I would suggest that C. limans Sykes should be struck out of the New Zealand fauna.

The following note by Mr. Edwin Ashby is on the paratype, since disarticulated:—

“The specimen is in a much-damaged condition, half of the first four valves being missing. An examination under a hand-lens at once showed that it was a member of the genus Callochiton, for the girdle is clothed with the needle-like or rod-like scales so characteristic of that genus. The strong longitudinal ribbing of the pleural areas of the median valves places it as a near relative to the rare Australian Callochiton mayi Torr. Girdle—The girdle needles are much coarser than those of mayi, although very similar in character. The shell is slightly more carinated than mayi, though the side slope is slightly rounded in both. The longitudinal ribbing in mayi is flatter on the upper side, reminding one of weatherboarding, whereas in the specimen under examination the longitudinal ribs are true ribs, equally raised on either side, and are also subgranulose, very similar to the ribbing of Lorica cimolea. The lateral areas in this specimen from Kapiti are strongly raised and strongly toothed on the posterior margin, the area is convex, finely granulose with strong concentric growth-ridges; whereas in mayi the lateral area is almost smooth, both the anterior and posterior margins raised, not toothed, slightly granulose only, making this area longitudinally concave, some growth-sulci are present. The anterior valve in mayi is minutely subgranulose, whereas in the species under review it is markedly granulose with toothed margin.”

Since writing the above a living specimen of Callochiton kapitiensis was obtained (in February, 1925), adhering to the under-surface of an Astraea heliotropium (Martyn), which had got caught on a fishing-line near Kapiti Island. It is slightly smaller than the holotype, which is an old specimen; the present specimen was measured before being dried.

Colour.—Shell light brown, the lower two-thirds of lateral areas of valves 3–5 dark brown; tail-valve dark brown with a white stripe from mucro to margin. Girdle same colout as shell, faintly mottled with dark brown, with fine hair-like spicules scattered about it, and a very delicate fringe at the edge.

Plaxiphora zigzag (Hutton). (Plate 100, figs. 5–6.)

Tonicia zig-zag Hutton, 1872.

As this and the following species have not hitherto been adequately figured, I give drawings of the holotype. Hutton's description appears in Trans. N.Z. Inst., vol. 4, p. 180, 1872.

For many years this species was merged with Plaxiphora caelata (Reeve), but Iredale (2) has recognized it as a distinct species.

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Fig. 1.—Callochiton empleurus (Hutton): radula.
Fig. 2.—Callochiton kapitiensis n. sp.: holotype.
Fig. 3.—Callochiton kapitiensis n. sp.: lateral view.
Fig. 4.—Callochiton kapitiensis n. sp.: girdle-scales.
Fig. 5.—Plaxiphora zigzag (Hutton): holotype.
Fig. 6.—Plaxiphora zigzag (Hutton): lateral view.
Fig. 7.—Plaxiphora ovata (Hutton): holotype.
Fig. 8.—Plaxiphora ovata (Hutton): lateral view.
Fig. 9.—Acanthochiton foveauxensis n. sp.: holotype.
Fig. 10.—Acanthochiton foveauxensis n. sp.: lateral view.
Figs. 11, 12.—Acanthochiton foveauxensis n. sp.: radula.

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Fig. 1.—Acanthochiton foveauxensis kirki n. var. : holotype.
Fig. 2.—Acanthochiton foveauxensis kirki n. var. : lateral view.
Fig. 3.—Acanthochiton foveauxensis kirki n. var. : radula.
Fig. 4.—Acanthochiton foveauxensis kirki n. var. : radula.
Fig. 5.—Macandrellus oliveri n. sp. : holotype.
Fig. 6.—Macandrellus oliveri n. sp. : holotype, lateral view.
Fig. 7.—Macandrellus oliveri n. sp. : paratype, lateral view.
Fig. 8.—Macandrellus oliveri n. sp. : holotype, radula.
Fig. 9.—Macandrellus oliveri n. sp. : holotype, radula.
Fig. 10.—Lorica haurakiensis Mestayer : radula.
Fig. 11.—Dentalium marwicki n. sp. : holotype.
Fig. 12.—Dentalium marwicki n. sp. : holotype, transverse section.

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Plaxiphora ovata (Hutton). (Plate 100, figs. 7, 8.)

Acanthochaetes oratus Hutton, 1872.

Hutton's description appears in Trans. N.Z. Inst., vol. 4, p. 182, 1872.

Suter, in Man. N.Z. Moll., 1913, pp. 1079–80, places it as a synonym of P. egregia A. Adams, 1866, on Iredale's authority (4); but in 1917 I sent several specimens to Mr. Suter, and he confirmed my doubts as to its specific identity, as his note following clearly states:—

“Before opening your box I looked over my spirit specimens, and there I found one specimen of P. egregia I once, long ago, collected at New Brighton. Most certainly it is distinct from P. ovata. My specimen is larger than yours. The sculpture of the valves is almost exactly alike, but the lateral-pleural areas I found to have 25–26 longitudinal riblets on each area, against about 20 in P. ovata. The chief differences are in the outline of the shell, ratio of width to length, also that of the fourth or fifth intermediate should be stated. If you disarticulate a specimen of each you may find differences in the sinus, the sutural laminae, position of slits, &c. The radulae also may show differences.”

Moreover, A. Adams notes “unknown habitat,” though there are other specimens conspecific with it in the British Museum.

I believe that P. egregia A. Adams is the commoner species in New Zealand, but at present am decidedly of opinion that P. ovata (Hutton) should be recognized as at least a readily separable variety, if not as a distinct species.

Acanthochiton foveauxensis n. sp. (Plate 100, figs. 9–12.)

A. rubiginosus (Hutton), 1872; Man. N.Z. Moll., 1913, p. 29.

Shell oblong, small, surface granular, side slopes straight.

Anterior valve—5 indistinct radiate ribs, the granules on central rib larger than the others. Median valves—the centre of jugum smooth, with a narrow, triangular, longitudinally striate portion on either side. Lateral areas slightly raised, pleural and lateral areas closely covered with variable-sized granules. Valves subcarinate, beaked. Posterior valve small, mucro central, posterior slope lightly concave; granules mostly smaller than on median valves. Mantle fleshy, 4 mm. in width before drying, with a dense covering of very fine spicules giving a silvery or golden sheen in some lights. On either side are 7 sutural tufts of slightly larger bristles, and 4 in front of the head-valve. These bristles are very friable and it is rare to find a perfect tuft; there is also a fringe of very fine spicules round the edge of the mantle, but the slightest friction destroys it.

Colour very variable; in holotype, jugum reddish with triangular white stripe on either side, shading to deep purple at edges. While wet the mantle was yellowish, rather darker round head-valve, irregularly blotched with purplish-brown, sutural tufts nearly surrounded by whitish patch.

Variations.—There is considerable variation in coloration in both shells and girdles, before drying. The girdles mostly yellowish-brown with white spots round sutural tufts, and purplish blotches. On the valves the colour is extremely variable. While a purplish-pink is the predominant tone, the edges of some specimens are dark purple, with many of the granules green, and in a number of specimens the jugum of the second valve is bright orange. Occasionally a bright blue-green one is found.

The jugal area of many specimens differs from the typical form in being finely granular rather than striate, the granules more crowded, and lateral areas less clearly defined.

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Interior white, with a large rose-pink patch in centre of valves 1–7, tail-valve only showing a slight trace of colour.

Insertion plates well developed, lateral valves with 1 slit, head-valve 4 slits; in tail-valve the number of slits very variable, mostly 4–7; but of a considerable number of specimens examined one had only 3, and another 13; the teeth nearly vertical. Insertion plate narrow and marked between the slits by shallow grooves; the teeth on the head-valve are also grooved. Valve-callus well developed. Sinus well marked, lightly convéx.

Length, 15 mm.; width, 13 mm.; but the holotype is much contracted, and by no means the largest specimen.

Locality.—Foveaux Strait, on the oyster-beds.

Holotype in Dominion Museum.

Acanthochiton foveauxensis var, kirki n. var. (Plate 101, figs. 1–4.)

In most particulars the foregoing description of the species applies equally to this variety, which seems to be sufficiently separable as a variety, and it gives me much pleasure to associate Professor H. B. Kirk's name with this particularly pretty form, in grateful recognition of his unfailing kindness.

Differences.—The most easily seen difference is the more regular diagonal arrangement of the granules, clearly shown in Plate 101, fig. 1; also, these granules are rather square and flatter than in the species, less crowded, especially on the pleural areas, and slightly smaller. Another frequent difference is coloration; but this is not a constant feature, many having the colour of A. foveauxensis; a considerable number have some or all the valves a deep old rose, and some show traces of light brown. The orange patch on the jugum also occurs.

This variety is separated on the sculptural difference, which is found in very young as well as adult specimens.

Length (holotype in Dominion Museum), 12 mm.; width, 11 mm. A contracted specimen, of average size.

Macandrellus oliveri n. sp. (Plate 101, figs. 5–9.)

Shell narrow-oval, high-arched, suface dull, closely covered with small scale-like granules.

Anterior valve with 5 low very indistinct radiating ribs, slightly beaked, granules on ribs very slightly larger than elsewhere. Median valves—jugum smooth between the numerous minute pits. Lateral areas raised. Valves beaked. Posterior valve small, mucro median, rather prominent, posterior portion sharply concave. Mantle broad, probably fleshy, 7 sutural pores on each side, 4 in front of head-valve, which in life evidently had tufts of rather long bristles, also probably fine spicules all over the mantle. Interior insertion plates (from a paratype) broad, rounded, but dropping steeply down to the nearly straight sinus. Head-valve with 5 slits, teeth about one-third total height of valve. Median valves 1 slit. Tail-valve 9 slits, of which the first and ninth are the most decided.

Colour inside of valves a dirty greenish-white, but another specimen pinkish-white. Externally the shell is a dull brown, slightly darker along the ridge.

Length of holotype, 27 mm.; width, 14 mm. (a dried specimen).

Localities.—Coromandel Peninsula, Hauraki Gulf, 20 fathoms (type); Cape Kidnappers, Hawke's Bay, 15–25 fathoms.

Named in honour of Mr. W. R. B. Oliver, who presented the holotype-and some paratypes to the Dominion Museum.

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As shown in Plate 101, figs. 6, 7, there is some variation in the size of the granules.

The size of the teeth on the head-valve and the character of the insertion plates of the median valve, with the overhanging mucro on the tail-valve, have led me to place this species in Macandrellus, rather than in Acanthochiton, where it was first placed.

Its nearest ally is Macandrellus mariae (Webster), which it closely resembles in sculpture and in the very peculiar tail-valve.

For the accompanying note on the radula (Plate 101, figs. 8, 9) I am indebted to Mr. Oliver: “Median tooth narrow, outer centrals with a broad cutting-edge. Laterals large, with long bases and a broad black cusp with two long sharp pointed cutting-points. Inner marginals with dark-brown pointed cusps, the third much longer than the others; outer marginals trapezoid.”

Radula of Lorica haurakiensis Mestayer. (Plate 101, fig. 10.)

Centrals expanded distally into wide curved cusps. Lateral with a large black cusp terminated by a single strong sharp point. Third marginal with a long pointed cusp; outer marginals oblong, increasing in size outwards.

Dentalium marwicki n. sp. (Plate 101, figs. 11, 12.)

Shell small, lightly curved, tapering.

Sculpture.—9 strong rounded ribs, which tend to become obsolete in old specimens. Anterior aperture thin, slightly oblique, the ribs only faintly marked internally. Posterior orifice small, with a very thick wall.

Length, 20 mm.; breadth, 2.5 mm.

Localities.—Castlecliff (lower bed), Pliocene (type). Recent specimens are found in dredgings from Manukau Harbour; off Oamaru, 50 fathoms; Otago Heads, 60 fathoms (H. J. Finlay); Hen and Chickens Islands, 25–33 fathoms; Great Barrier Island, 110 fathoms (9). In this last record Dentalium nanum Hutton is recorded by Murdoch and Suter, but I have broken fragments of both species taken from a little sample of that particular dredging.

Holotype in Dominion Museum.

Remarks.—In old specimens the aperture becomes almost circular. The number of ribs varies from 8 to 10 in individual specimens, the last number being apparently exceptional.

This species is nearly allied to D. nanum Hutton, from which it is distinguished by its fewer and more rounded ribs.

Named in honour of Dr. J. Marwick, of the Geological Survey, who was the first to recognize it as a new species, and in grateful acknowledgment of his unfailing kindness and help.

References.

1. Trans. N.Z. Inst., vol. 4, p. 180.

2. Trans. N.Z. Inst., vol. 47, p. 421.

3. Trans. N.Z. Inst., vol. 4, p. 182.

4. Proc. Malac. Soc., vol. 9, 1910, p. 93.

5. N.Z. Moll., 1913, p. 39.

6. Proc. Malac. Soc., vol. 2, 1903, p. 93.

7. Man. Conch., vol. 14 (ser. 1), p. 176.

8. Proc. Malac. Soc., vol. 2, 1903, p. 93.

9. Trans. N.Z. Inst., vol. 38, p. 303.