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Volume 4, 1871
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Art. XXIII.—On the New Zealand Chitonidæ.

(With Illustrations.)

[Read before the Wellington Philosophical Society, 25th November, 1871].

The Chitons form a very distinct family of the Mollusca, easily recognised by their oval or oblong form, covered by several shelly plates or valves, which give them something the appearance of those Isopod crustaceans commonly known as Wood-lice (Oniscus). The shell is composed of eight transverse moveable valves, the anterior edge of each being covered by the posterior edge of the

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one next in front; these valves are inserted into a tough ligament called the mantle, which holds them all together, and which expands into a broad margin round the animal. (Pl. IX.) The margin of the mantle presents many differences, which are used to divide the family into various genera. Sometimes it is covered with small imbricated scales, sometimes with spines, while in many species it is nearly smooth, or tomentose with short hairs. The anterior and posterior valves are smaller than the others, and generally rounded on the outside margins; the intermediate ones are broader than long, and elevated in the centre, either by being uniformly arched, or by each side being more or less flattened so as to form two sides of a triangle. These intermediate valves are usually divided into a dorsal, or median, area, and a triangular lateral area on each side, which are called respectively the median and lateral areas. The sculpturing on the lateral areas is generally different from that on the median areas, while it is almost always the same as that on the anterior and posterior valves, or terminal areas.

The animal is of an oval or oblong shape, with a long and broad foot rounded at each end. The head is not furnished with eyes nor with tentacles, but has a waved membranous hood surrounding the mouth. The tongue is long, spirally rolled, and armed with hooked horny teeth. The branchiæ, or breathing organs, are in the form of a series of small triangular leaves, and are situated in a row on each side of the body, between the mantle and the foot. The sexes are distinct. They adhere to rocks, or shells, sometimes even to fish, and when detached roll themselves up; a few are found creeping on sand. They generally live between high and low water marks, but some small species inhabit the sea to a depth of twenty-five fathoms. Some fix themselves on the upper surfaces of rocks, and, when the tide is out, bear the full heat of a tropical sun on their backs, while others are only to be found during very low tides, and are seldom exposed to the air. The greater number, however, inhabit the bottoms of rock-pools, or the under surfaces of stones, and so always keep moist even when the tide is out.

Very little is known about their habits further than that when covered with water they move slowly from place to place in quest of food, which is supposed to be entirely vegetable.

They adhere to the rocks with great tenacity, and in order to collect them without breaking the shell they must be taken by surprise, the blade of a knife being slipped suddenly under them and one side lifted up. If the animal is at once removed from the shell the mantle contracts, and cannot be straightened out again without great risk of breaking or displacing the valves. The best method of proceeding is to place the animals, immediately after they have been collected, on small flat stones, or pieces of slate, under the water, when they will soon attach themselves, and may then be removed, and the stones, with

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the Chitons on them, wrapped up in separate pieces of paper. On arrival at home they should be placed in a basin of fresh water for a short time, then removed, and either tied down to the stones with string, or a light weight put on each, and put into a dry place. After two or three days, when the margin has got quite hard, they can be easily removed from the stones, and the animal taken out, and after another day or two for the interior to dry, they will be ready for gumming down on to cards, on which the name, locality, date of collecting, and the position in which they were found, should be written.

The genera are founded upon the shape and covering of the mantle; the species chiefly on the shape and sculpturing of the valves, which latter is easily made out with the aid of a pocket lens. The colour varies very much, and can never be taken as a specific distinction, although in many cases it may assist the beginner in naming his collection; those of the margin of the mantle, and of the spines upon it, are, however, much more constant than those of the valves. The shape, or the proportion of breadth to length, is generally pretty constant, but the size of individuals, especially the larger kinds, varies considerably, and too much weight must not, therefore, be attached to it. The shape of the posterior margin of the valves will also be often found very useful when the specimen is rubbed or eroded. The teeth on the tongue, and the branchial laminæ are also of great importance in determining the species, but as these parts are not easily examined and preserved, they will not be found to be so useful as the other characters.

Chitons are found in all countries, but they are not so abundant in the northern hemisphere as in the southern, nor on the shores of the Atlantic as on those of the Pacific, neither are they so common nor so large in cold latitudes as in warm, the sub-tropical portion of the South Pacific appearing to be their head-quarters. In England only about a dozen species have been found, while twenty-one are here described as already known to inhabit New Zealand, and undoubtedly many more have yet to be discovered, for, with the exception of M. Quoy in the ‘Astrolabe,’ and the late Dr. Sinclair, few people have collected them. Altogether nearly 300 species are now known to science.

In a fossil state about twenty-four species have been found, some of them dating so far back as the Upper Silurian period.

I have not thought it necessary to give figures of the different species, for, with a moderate amount of attention, they will be readily made out from the descriptions, and I quite agree with Messrs. Kirby and Spence that they who begin their zoological studies by turning over figures usually end them there, and never attain to that nameless tact in making out species that can only be the result of patient study.*

*

[Footnote] “Introduction to Entomology,” Vol. IV., p. 569.

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Genus Chiton. Lin.

Mantle covered with scales; exposed portion of the valves broader than long. All parts of the world.

A. Scales distinct (Lophyrus).
Chiton concentricus.

Chiton concentricus, Reeve, “Conch. Icon.,” pl. 16, f. 95. Lophyrus concentricus, Angas, “Pro. Zool. Soc.,” 1867, p. 221.

Oval; mantle with rather large scales; valves compressed on each side, keeled; posterior margins pointed; terminal and lateral areas closely concentrically ribbed; median areas distinctly longitudinally ribbed; dorsal line smooth.

Length, 1 inch; breadth, .5 inch.

Colour.—Mantle white or pinkish, irregularly banded with yellowish brown; terminal and lateral areas yellowish brown, median areas white with yellowish brown ribs.

This species is also found in Australia.

There are several specimens in the Colonial Museum, locality not stated, probably dredged.

Under stones at very low tide (Angas).

Chiton canaliculatus.

Chiton canaliculatus, Quoy and Gaim., “Voy. Astrol.,” Vol. III., p. 394. Chiton canaliculatus, Desh., “Anim. sans Vert,” Vol. VII., p. 502.

Oblong; mantle with moderate sized scales; valves compressed on each side and keeled; posterior margins straight, crenulated on their sides; terminal and lateral areas with radiating moniliform ridges; median areas with longitudinal ridges; dorsal line smooth.

Length, 1 inch; breadth, .5 inch.

Colour.—Mantle pink, with about twenty transverse yellowish pink bands; terminal and lateral areas deep pink; median areas yellowish pink, sometimes longitudinally varied with black.

Several specimens are in the Colonial Museum, which were dredged off the island of Kapiti, in Cook Straits.

Chiton pellis-serpentis.

Chiton pellis-serpentis, Quoy and Gain, “Voy. Astrol,” Vol. III., p. 381. Chiton pellis-serpentis, Desh., “Anim. sans Vert.,” Vol. VII., p. 508.

Oval; mantle with moderate sized scales; valves elevated, rounded, solid, opaque; posterior margins curved, meeting in an obtuse point on the back;

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terminal areas with radiating moniliform lines; lateral areas of intermediate valves with curved radiating ribs, concave behind, and crossed by curved longitudinal furrows, which are concave upwards; median areas slightly longitudinally striated; dorsal line smooth and polished on the anterior parts of the valves, but striated on the posterior parts.

Length, 1.5 inch; breadth, .75 inch.

Colour.—Mantle yellowish or greenish white, with about twenty transverse black bands; valves generally greenish black, passing into yellowish on the back, and with a triangular black spot, with its apex pointing backwards, along the dorsal line of all the intermediate valves. It is generally much eroded, but the size and colour of the scales on the mantle are always sufficient to distinguish it from other New Zealand species.

Abundant on rocks between high and low water marks.

Chiton Sinclairi.

Chiton Sinclairi, Gray. “Dieff. New Zealand,” “Vol. II., p. 263.

Oval; mantle with moderate sized scales; valves elevated and flattened on the sides; posterior margins straight, with a slight central point, and crenulated on the sides; terminal areas with radiating moniliform ribs; lateral areas with flat, sub-moniliform, radiating ribs, crossed by a few irregular transverse furrows; median areas finely longitudinally striated on the sides, but smooth and polished on the back.

Length, 1.35 inch; breadth, .7 inch.

Colour.—Mantle brown, transversely banded with black; valves pale brown, longitudinally varied with paler brown and black. The scales on the mantle are smaller and flatter than those of pellis-serpentis.

I have only seen one specimen which was in the collection of the late Mr. W. Swainson; locality not stated.

Chiton Quoyi.

Ch. viridis, Quoy (nec Chemn.), “Voy. Astrol.,” Vol. III., p. 383. Ch. Quoyi, Desh., “Anim. sans Vert.,” Vol. VII., p. 509. Ch. glaucus., Gray. nec Quoy. et Gaim. Lophyrus glaucus, Angas, “Pro. Zool. Soc.” 1867, p. 222.

Oval; mantle with moderate sized scales; valves elevated, flattened on each side; posterior margins slightly concave, with a small central point; the anterior valve, the greater part of the posterior valve, and the lateral areas of the intermediate valves with fine radiating striæ; median areas very finely longitudinally striated.

Length, 1.5 inch; breadth, .75 inch.

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Colour.—Generally dark olive green, or blackish green when dry, but sometimes brown, or green rayed with brown, and the mantle is sometimes varied with white.

Common under stones in pools left by the retreating tide.

Found also in Australia.

B. Scales minute (Lepidopleurus).
Chiton sulcatus.

Ch. sulcatus, Quoy and Gaim., “Voy. Astrol.” Ch. sulcatus, Desh., “Anim. sans Vert.,” Vol. VII., p. 512.

Oval; mantle with small scales; valves depressed, slightly flattened on each side; posterior margins straight, crenulated on the sides; terminal and lateral areas finely granulate; median areas with fine distant longitudinal ribs.

Length, .4 inch; breadth, .25 inch.

Colour.—Mantle reddish brown; valves whitish brown, dull.

Specimens from Kapiti are in the Colonial Museum; it is also found in Australia. I do not feel quite sure as to the identification of this species, for I have no Australian specimens for comparison, and the description in Lamark is not very definite, but I think that the difference between the two, if any, must be very slight.

Chiton longicymbus.

Ch. longicymba, De Blain., “Sow. Conch. Mus,” f. 67. Lepidopleurus longicymba, Angas, “Pro. Zool. Soc.,” 1867, p. 222.

Oblong; mantle with very minute scales; valves rounded; posterior margins straight, or slightly concave; terminal areas with fine radiating moniliform lines; lateral areas with radiating ribs crossed by rather deep, curved transverse furrows; median areas of both terminal and intermediate valves finely punctate.

Length, 1.4 inch; breadth, .65 inch.

Colour.—Brown, variously tinted with green, yellow, or whitish, sometimes pink on the back when rubbed; often entirely greenish brown, minutely freckled with yellow; often brown with a broad white stripe down the back.

Very variable both in shape and colour.

Common under stones.

Found also in Australia.

Chiton empleurus. sp. nov.

Oblong; margin with very minute scales; valves rather elevated and flattened on each side, sub-carinate; posterior margins slightly concave, with

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a small central point; terminal and lateral areas raised above the rest minutely punctate; median areas minutely punctate, sometimes with a row of deep longitudinal pits along the anterior edges of the raised lateral areas.

Length, .75 inch; breadth, .3 inch.

Colour,—Uniform yellowish pink.

Founded on two specimens in the Colonial Museum, locality not stated.

Chiton rudis. sp. nov.

Oblong; margin with minute scales; valves elevated, flattened on the sides, not keeled; apex of anterior valve recurved, with its posterior margin slightly convex at the sides, and deeply concave in the centre; posterior margins of intermediate valves straight; posterior valve rather small; apex posterior pointing and emarginate; anterior valve, and lateral areas, with radiating moniliform ribs; posterior and median areas widely, but rather irregularly, deeply longitudinally furrowed, with narrow ridges between.

Length, 1.75 inch; breadth, .75 inch.

Colour.—Margin grey, with broad irregular reddish brown transverse bands; valves greyish brown; interior greyish white.

Founded on a specimen in the Colonial Museum, locality not stated.

Genus Tonicia. Gray.

Margin of the mantle simple, naked, nearly smooth, or velvety; last valve entire.

South America, Australia, Greenland.

Tonicia undulata.

Ch. undulatus, Quoy and Gaim., “Voy. Astrol.” Acanthopleura undulata, Gray, “Dieff.” Vol. II., p. 245.

Oval; valves rounded, polished, sub-carinate; posterior margins straight, produced into a rather acute central point; terminal area of anterior valve, and lateral areas of intermediate valves, with indistinct radiating moniliform ridges; posterior valve, and median areas of anterior and intermediate valves with waved transverse striæ.

Length, 1.15 inch; breadth, .55 inch.

Colour.—Mantle reddish brown; valves generally green, inclining, more or less, to yellowish on the back, with the waved striæ brown; sometimes the valves are greyish green, with many of the undulating striæ white.

Not uncommon under stones at low water.

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Tonicia rubiginosa.

Chiton rubiginosus. Swains. Ms.

Oblong; margin slightly tomentose; valves rather elevated, sub-carinate, flattened on each side; posterior margins straight, produced into an acute central point; lateral areas indistinct, the whole surface rather coarsely granular, the granules smaller on the back.

Length, .45 inch; breadth, .2 inch.

Colour.—Pink, getting yellowish on the back.

This species is named from a specimen from the late Mr. W. Swainson's cabinet, and now in the Colonial Museum, which is labelled as coming from the island of Kapiti. I do not know whether Mr. Swainson ever published a description of it, but have retained the name written on it to prevent confusion, if such should have been the case. It is also in the Colonial Museum collection from Kapiti.

Tonicia Zig-Zag, sp. nov.

Oblong; mantle slightly tomentose; valves slightly flattened on each side, but not keeled; posterior margins sloping backwards into a point, crenulated on the sides; anterior valve with 9 radiating ridges, crossed by fine concentric zig-zag striæ; lateral areas with two, on each side, radiating ridges crossed by fine zig-zag striæ; posterior and median areas with very fine oblique striæ diverging from the dorsal line outwards and forwards, crossed by others diverging outwards and backwards, forming an “engine-turned” pattern.

Length, .88 inch; breadth, .31 inch.

Colour.—Mantle white; valves greyish black, with a white stripe on each side of the dorsal line; interior greenish blue.

A single specimen is in the Colonial Museum, locality not stated.

Tonicia corticata. sp. nov.

Oval; margin naked; valves much depressed; posterior margins slightly concave; lateral areas bounded on either side by a flatly nodulose ridge, the space between being obliquely striated, the striæ running outward and backward; median areas rugose, without either distinct lines or granules.

Length, 1.25 inch; breadth, 1.13 inch.

Colour.—Margin black when dry; valves grey; inside white, covered over with white coralline growth, and small marine algæ.

Founded on a specimen in the Colonial Museum, locality not stated.

Genus Acanthopleura.

Mantle covered with long spines.

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Acanthopleura complexa. sp. nov.

Chiton aculeatus, Quoy and Gaim., nec Lin. nec Barnes. Acanthopleura aculeatus, Gray, “Dieff. N.Z.,” Vol. II., p. 245.

Oval; margin broad, velvety, with long spines scattered over it; valves depressed, flattened on each side, sub-carinate; posterior margins not covering the next at the corners, rather convex, and pointed in the centre; anterior valve with radiating moniliform ridges; lateral areas of intermediate plates granulose with two prominent, radiating, slightly curved ridges on each side; median areas with finely granular transverse waved lines, which pass imperceptibly into the larger lateral granulations; posterior valve small, like the intermediate ones; centres of valves punctate internally.

Length, 1 inch; breadth, .5 inch.

Colour.—Margin reddish brown, varied with darker; valves greyish, more or less varied with yellowish white, yellow, or brown.

From the collection of the late Mr. W. Swainson, locality not stated.

Acanthopleura nobilis.

Acanthopleura nobilis, Gray, “Dieff. N.Z.,” Vol. II., p. 245.

Mantle rugose, rough, with scattered long tapering brown bristles; valves brown, convex, evenly rounded, with very minute dots like shagreen, the lateral area slightly marked with three or four indistinct rays; inside white; length three inches (Gray).

I have only seen a single valve.

Genus Acanthochætes. Leach.

Margin of the mantle spinulose, with nine bundles of spines along each side.

Australia, Europe.

Acanthochætes biramosus.

Chiton biramosus, Quoy and Gaim.; “Voy. Astrol.,” Vol. III., p. 378. Chiton biramosus, Desh., “Anim. sans Vert.,” Vol. VII., p. 516. Acanthochætes biramosus, Gray, “Dieff. N.Z.,” Vol. II., p. 246.

Oval, reddish, surrounded with twice branched hairs, margin rough; valves nearly flat, greenish red or white, transversely striated in front. Remarkable for having its mantle covered with very short hairs of an intense brownish red. Upon the mantle are placed rough and bifurcating hairs, forming a double rank; the valves are nearly straight, and have no keel on the back; they are greenish white and surrounded by a circle of reddish brown (Deshayes).

I have seen no specimens.

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Acanthochætes ovatus. sp. nov.

Ovate, attenuated in front; margin spiny, with nine small bundles along each side; valves flatly triangular, sub-carinate, posterior valve very narrow, apex re-curved; posterior margins of the anterior plate sloping backwards into a point, those of the posterior plates nearly straight; anterior valve with ten, and lateral areas with two on each side, radiating nodulose ridges; median areas with slightly waved longitudinal ridges; dorsal line smooth.

Length, .6 inch; breadth, .5 inch.

Colour.—Mantle pale reddish brown; spines white; valves greenish white; yellowish on the dorsal line.

Several specimens in the Colonial Museum, locality not stated.

Acanthochætes hookeri.

Acanthochætes Hookeri, Gray, “Dieff. N.Z.,” Vol. II., p. 262.

Oblong; mantle spiny with nine large radiating tufts of spines on each side; valves flatly triangular, sub-carinate; posterior margins slightly convex, with an obtuse central point; terminal and lateral areas granulose; median areas smooth; lateral areas very large.

Length, 1 inch; breadth, .4 inch.

Colour.—Mantle brown; spines pale green; valves generally greyish black, more or less varied with yellowish; often yellowish or reddish on the dorsal line; occasionally greenish.

Several specimens in the Colonial Museum, Wellington Harbour; it is not uncommon on stones below low water mark.

Genus Katharina. Gray.

Valves partly hidden on each side by an expansion of the mantle, sides smooth; uncovered portions of the valves as broad as long.

West Coast of South America.

Katharina violacea.

Chiton violaceus, Quoy and Gaim., “Voy. Astrol.,” Vol. III., p. 403. Chiton violaceus, Desh., “Anim. sans Vert.,” Vol. VII., p. 519. Acanthochætes violaceus, Gray, “Dieff. N.Z.,” Vol. II., p. 246.

Elongated oval; margin smooth; valves rounded, depressed; posterior margins waved; anterior valve granulose, six-sided, separated by flat nodulose lines; posterior valve small, rounded, granulose; lateral areas small granulose; dorsal line smooth, with several irregular rows of longitudinal punetures on each side; sides granulose; nine bundles of spines on each side.

Length, 1.5 inch; breadth, .65 inch.

Colour.—Mantle brown, valves violet.

In rock basins near low water mark, Cook Straits.

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Genus Cryptoconchus. Guilding.

Mantle large, enveloping the greater part of the valves; exposed portions of valves longer than broad.

California.

Cryptoconchus zelandicus.

Chiton Zelandicus, Quoy and Gaim., “Voy. Astrol.,” Vol. III., p. 400. Chiton Zelandicus, Desh., “Anim. sans Vert.,” Vol. VII., p. 518. Chitonellus Zelandicus, Gray, “Dieff. N.Z.,” Vol II., p. 246.

Elongated oblong; margin scaly, with a row of short spines round the edge; mantle large, continuous under the apex of each valve; valves depressed, rounded, sub-carinate; posterior margin concave with an acute point; exposed portions of valves small, smooth on the dorsal line, granulose on each side; nine tufts of spines on each side, situated over the valves.

Length, .45 inch; breadth, .15 inch.

Colour.—Blackish brown; exposed portion of the valves yellowish; spines yellowish brown.

Two specimens are in the Colonial Museum, locality not stated; obtained by dredging.

Cryptoconchus monticularis.

Chiton monticularis, Quoy and Gaim., “Voy. Astrol.,” Vol. III., p. 406. Chiton monticularis, Desh., “Anim. sans Vert.,” Vol. VII., p. 519. Amicula monticularis, Gray, “Dieff. N.Z.,” Vol. II., p. 246.

Oblong; mantle smooth, covering the whole body except a small linear opening at the apex of each valve; valves depressed, rounded; posterior margins convex and emarginated; exposed portions of valves smooth; nine bundles of spines on each side, situated over the valves.

Length, 1 inch; breadth, .45 inch.

Colour.—Dark reddish brown when dry; inside greenish grey.

Two specimens are in the Colonial Museum, locality not stated; obtained by dredging.