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Chiton huttoni, n. sp. Plate XVIII, figs. 1–6.
General Appearance..—Shell oblong-ovate, angularly raised, valves striated throughout, jugum smooth, girdle with rounded scales; colour yellowish-olive, dull to dark green or brick-red; interior whitish.
The flatly convex anterior valve has seventeen to twentyfour subequal riblets reaching to the apex, and broken up by concentric rugæ of growth; sometimes a few riblets are interspersed which do not extend to the apex; the latter is smooth, and mostly a little excavated posteriorly.
The intermediate valves have the jugum smooth, projecting a little behind; the pleural tracts have about twenty to twentyfive furrows on each side, which near the central area are narrow and not deep, but usually widening and deepening on approaching the margin. Sometimes they are in breadth equal to the riblets, but in some specimens they are narrower. They extend the whole length of the pleural areas. The lateral areas are strongly ribbed, the ribs broken up by the continuance of the grooves on the pleural tracts. Their number is very variable—the usual number is three to four, but sometimes as many as five are found—and some of them may be divaricating, which, however, is not the rule.
The posterior valve has the mucro very little behind the middle; the central area is flatly convex, with the same furrows as the pleural tracts of the intermediate valves; the posterior slope is concave, and the posterior area has eighteen to twenty strongly granose riblets reaching up to the apex.
The girdle bears roundish medium-sized and compactly imbricating polished scales, which under a powerful lens show faint striation.
The colour is very variable; the most common is yellowish-olive, then dull-green is met with, and one of these specimens has the end valves blackish-green; one specimen is brownish-black, and one brick-red. The girdle has the same colour as
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the valves; sometimes dark bands of variable width and irregular in distribution may be seen.
The interior is mostly bluish-white, pinkish-white in the red specimen. The sinus is deep and narrow, pectinate. The slits on a specimen I disarticulated are: head-valve 9, intermediate válves 1–1, posterior valve 15. All teeth are blunt and pectinate; those of the tail-valve are very unequal in breadth. The valve-callus is rather prominent.
Divergence, 115°. Length, 34 mm.; breadth, 20 mm.
Hab.—Near Dunedin; collected by Mr. A. Hamilton, now Director of the Colonial Museum, who kindly gave me a few specimens many years back.
Type in my collection.
Remarks.—It is at the special request of Miss M. K. Mestayer, of Wellington, that this mollusc is named in honour of Captain Hutton, F.R.S.,&c., in acknowledgment of his continuous very kind help she had the honour to enjoy in her conchological studies. Miss Mestayer found a number of years back a Chiton at Lyall Bay, which Captain Hutton and myself then thought to be a new species, and lately Miss Mestayer kindly lent me the specimen for description, under condition that it should bear Captain Hutton's name, to which I, of course, with greatest pleasure agreed. However, on closely examining the specimen I found it to be a red-coloured mutatio of Chiton æreus, Reeve, one of our rare species. I am very glad indeed to have, nevertheless, an opportunity to comply with Miss Mestayer's wish and unite the name of our honoured leader in natural history with the species.
I once sent a specimen to Mr. E. R. Sykes in London, asking him to be good enough and compare it with the type of Reeve's æreus in the British Museum. He, with his usual kindness, however, informed me that it was not the supposed species, but seemed to agree with a specimen in the British Museum from New Caledonia which bears the manuscript name perpunctatus, Cpr. I do not doubt for a moment the well-known great ability of Mr. Sykes, but, considering that the affinities of the marine Mollusca of New Caledonia and New Zealand are very slender, and having no material from the former country for comparison, I thought it advisable not to take up that manuscript name There may be differences between the two species which a short examination would not reveal.
Chiton huttoni is in its sculpture nearest allied to C. canaliculatus,Q. and G., C. æreus, Reeve, C. limans, Sykes, and C. stangeri, Reeve; but the diagnosis and figures now given will easily help to separate it from the other species. I have not seen it yet from any other locality.
11—Trans.
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Helcioniscus mestayeræ, n. sp. Plate XVIII, figs. 7–9.
Shell solid, oval, slightly narrower in front, depressed-conical; apex at about the front fourth, sharply pointed. Surface sculptured with numerous (about fifty) broad depressed radiating ribs which are crossed by fine concentric striæ. Colour dark-olive with rather distant indistinct bluish-grey radiating bands.
Interior bluish-grey, with a silvery lustre. There are at irregular intervals about eleven broad radiating areas with chestnut-coloured spots and patches, sometimes arranged in a divaricating pattern; between these areas are several radiating bands of an alternately darker and lighter grey colour. These characters are very distinctly visible when the shell is held up against the light, and give it a very beautiful appearance. The central callus is well defined; its colour is reddish-orange, lighter near the margin, finely and minutely dotted with yellow. The muscle-scar is about 3 mm. broad, but slightly impressed.
Length, 49 mm.; breadth, 39 mm.; altitude, 14 mm.
Hab.—Stewart Island.
Type in Miss Marjorie K. Mestayer's cabinet.
I have great pleasure in naming this beautiful species in honour of our most enthusiastic conchologist, Miss M. K. Mestayer.
The animal is unknown. It is quite distinct from any New Zealand species of Helcioniscus I have seen, but the general characters approach those of H. radians, Gm., more than of any other species.