Two New Molluscs of the Pectinidæ from 600 to 700 Fathoms, Four Hundred Miles West of New Plymouth.
[Received by Editor, 19th October, 1932; issued separately, June, 1933.]
The two important additions to our fauna which are described below were collected recently from deep-sea cable by Mr. W. Foster, of the cable steamer “Recorder.” The locality was about 400 miles west of New Plymouth, and the depth between 600 and 700 fathoms.
Both species belong to the Pectinidae, and one of them, the Palliolum, represents a genus new to our Recent fauna, although species of the closely allied Mesozoic genus Camptonectes are recorded from the Cretaceous of New Zealand. It is, in fact, doubtful if there is any real distinction between the genera Camptonectes and Palliolum.
The only other molluscs present were a number of juveniles of a thin, fragile, and very variable Anomia, which at that stage could not be separated with certainty from the common inshore species trigonopsis and walteri.*
The Anomias occurred on the valves of the Palliolum.
Genus Palliolum Monterosato, 1884.
Type (by subsequent designation, Cossmann and Peyrot, 1912): Pecten testae Bivona, Recent, Mediterranean.
Palliolum fosterianum n. sp. (Plate 40, Figs. 6 and 7).
Shell of moderate size for the genus, subcircular, convex, very thin, translucent white, having faint “Camptonectes” divaricating striations, and minute rather distant hollow granule-like scales, which occur on the concentric lines of growth. These scales are usually worn off in the middle of the valves, but remain intact at the sides, where they appear as several radial series. In the holotype, which is 20 mm. in height, the striations are about 8 per mm., and the concentric growth-lines 3 per 2 mm., at the middle of the shell. Hinge-line straight, ears unequal, produced a little longer anteriorly. Sculpture of anterior ear in right valve consists of six rows of imbricating radial ribs which are crossed by the concentric growth-lines. The posterior ear of the right valve and both ears of the left valve are without radial sculpture except for the growth-lines and “Camptonectes” striations. Byssal notch deep and wide, with a broad fasciole, and a ctenolium with four free teeth. Apart from the byssal notch the margins are entire, close fitting, thin, and not bevelled. The beaks are small, sharply pointed, and approximate.
[Footnote] * Finlay (1926, Trans. N.Z. Inst., vol. 57, p. 447) considers that trigonopsis and walteri are probably identical.
Interior glassy, polished, muscle-scar indistinct. Ligamentary pit very small and shallow.
Height 20 mm.; width of valves 19.75 mm.; width of hinge-plate 12 mm.; thickness (two valves) 6 mm. (holotype, fig. 6).
Holotype and several paratypes in Auckland Museum.
This new species appears very like the deep-water Atlantic Chlamys (Palliolum) chaperi Dautzenberg & Fischer.* The New Zealand species differs from the Atlantic one in being more circular, in having a proportionately longer hinge-plate, and in being without a constriction between the hinge-line and the disc; that is apart from the byssal sinus in the right valve.
Unlike the colourless, translucent fosterianum the Mediterranean genotype is brightly coloured, but on shell characters it is very similar to the New Zealand species.
The species is named after Mr. W. Foster, of the cable steamer “Recorder,” who, by collecting material from cables at every opportunity, has done much to further our knowledge of deep-sea life in Australasian waters.
Another related species is the deep-water Pecten kermadecensis E. A. Smith, which was dredged by the “Challenger” at Station 171, north of the Kermadec Islands, in 600 fathoms.†
Genus Chlamys Bolten, 1798.
Type (by subsequent designation, Herrmannsen, 1846–47): Pecten islandicus (Linnaeus) = Ostrea islandica Gmelin in Linnaeus, 1791 = Pecten islandicus Muller, 1776.
Chlamys kiwaensis n. sp. (Plate 40, Figs. 1–5).
Shell of medium size, thin, suborbicular, compressed, equivalve, but with ears very unequal. Sculptured with rather distant, rounded, partly scabrous, strong radial ribs with fine radially striated interspaces. Colour of both valves dull-white, but with the radials of the left valve only marked out in brownish-pink. Beaks small, sharply pointed, approximate. Anterior ears large, twice the length of the posterior ones. Right valve with a broad fasciole; ctenolium broad and rather shallow, with four free teeth. Anterior ear of right valve with four scabrous radial ribs, that bordering the hinge-line being widest. Posterior ear of right valve with four evenly spaced and equally developed scabrous radial ribs. In the left valve there are eight anterior and three posterior scabrous radials. The disc is sculptured with 31 simple narrow radials which bear towards the margin sharp imbricating spines. Interspaces from three to five times width of radials, smooth to the eye, but really delicately sculptured with
[Footnote] * Chlamys (Palliolum) chaperi Dautz. & Fischer. Station 584, 38° 31′ N., 26° 49′ 15″ W. in 845 metres. Dautzenbergh, Ph. 1927. Resultats des Campagnes Scientifiques du Prince de Monaco. Mollusques. Provenant des Campagnes Scientifiques du Prince Albert ler de Monaco dans I'ocean Atlantique et dans Le Golfe de Gascogne.
[Footnote] † Challenger Reports, Zoology, vol. 13, 1885, p. 302, Pl. 21, figs. 7 and 7a.
microscopic radial striae crossed by “Camptonectes”-like divarications. Ligamental pit small and shallow. Interior of shell dull white, with brownish-pink ribs showing through in right valve.
Height 33 mm.; width of valves 29.5 mm.; width of hinge-plate 16 mm.; thickness (two valves) 9 mm. (holotype).
Holotype and three paratypes in Auckland Museum (Figs. 3, 4, and 5).
The Tertiary Chlamys compitum (Marwick) from Chatton and Wharekuri is very similar to this new species, both having distant rounded scabrous simple radials without intermediate radials.
The name of the species is based upon the Maori for the ocean—Te moana nui a kiwa—the great ocean of Kiwa.
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Figs. 1. & 2.—Chlamys kiwaensis n. sp. (paratype). × ½
Figs 3. & 4.—Chlamys kiwaensis n. sp. (holotype). × ½.
Fig. 5.—Chlamys kiwaensis n. sp. (detail of sculpture, left valve of holotype) × 16.
Fig. 6.—Palliolum fosterianum n. sp. (holotype) × ½.
Fig 7.—Palliolum fosterianum n. sp. (paratype) × 3/2