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Volume 56, 1926
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New Species of Recent Mollusca.

[Read before the Auckland Institute, 25th November, 1924; received by Editor, 28th November, 1924; issued separately, 5th May, 1926.]

Plate 102.

Vexillum Bolten, 1798, Mus. Bolten., vol. 2, p. 138.

Vexillum antipodum n. sp. (Plate 102, fig. 1.)

Shell small, fusiform, rather solid and axially costate, ochreous, banded. with purple-black. Sculpture: all whoris except protoconch distinctly axially costate between sutures. Costae somewhat broadly rounded, beginning on the lower edge of whorl-shoulders and hardly reaching the sutures; there are also several moderately distant spiral lirae present on each whorl, in some cases extending over costae, stronger on lower half of body-whorl, where the ribs gradually become obsolete; shoulders below sutures with 2 or 3 fine spiral cords, the whole shell finely sculptured with axial growth-lines; neck of columella with 5–6 oblique fine ribs, the two upper separated from the others by a rather broad rounded groove. Protoconch smooth, of 1 ½ turns. Whorls 7, slightly angulated, with impressed sutures, outlines slightly convex, apex rounded, a little flattened above. Spire elevated, conical, very little higher than aperture. Aperture moderately narrow, oblique, nearly half height of shell, slightly angled above, with a short open almost straight canal somewhat crenulated on base owing to spiral ribs on neck of columella. Outer lip moderately rounded, solid, margin sharp. Columella subvertical, with 4 plaits, the two lower oblique, closer together than upper ones, which are more widely separated, and the top one nearly transverse; a narrow groove divides plaits from neck-spirals. Colour: ground-colour ochreous-buff, with a broad purple-black band on the lower half of body-whorl, also a very narrow band of same shade immediately above suture of penultimate whorl and two preceding it; the upper whorls of a lighter shade without sutural bands; protoconch flesh-coloured, base of columella orange.

Diameter. 4.2 mm.; height, 10 mm. Angle of spire, 70°.

Animal unknown.

Holotype and two paratypes in author's collection.

Habitat.—Cooper's Beach, Doubtless Bay (A. E. B.); type. Also obtained by Mr. W. La Roche, of Auckland, in the same locality.

Situation: Under loose boulders embedded in sand between tide-marks.

This species is the finest yet discovered in New Zealand, and is apparently restricted to very narrow limits, and not at all common. It appears to be more closely allied to V. planatum Hutton than to any other New Zealand, species, but is at once distinguished by the conspicuous colour-bands.

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Fig. 1.—Vexillum antipodum n. sp.; 4.2 × 10 mm.M
Fig. 2.—Ancilla crystallina n. sp.; 5.1 × 11.6 mm. 2a. Operculum, highly magnified.
Fig. 3.—Laevilitorina iredalei n. sp.; 1.5 × 2 mm.
Fig. 4.—Area sociella n. sp.; 5 × 2.2 mm. 4a. Interior.

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Ancilla Lamarck, 1799, Mem. Soc. Hist. Paris, p. 70.

Ancilla crystallina n. sp. (Plate 102, figs. 2, 2a.)

Shell small, ovate-elongate, semitransparent, white. Spire conical, short, less than height of aperture, apex mucronately rounded, outlines nearly straight. Whorls apparently 6, evenly covered with enamel except portion of protoconch which consists of 1 ½ turns, body-whorl gradually narrowly rounded towards base, of moderate size, outlines convex. Sculpture: spire very finely granulated, this feature extending to callus of upper portion of inner lip; lower half of body-whorl with very fine distinct growth-lines crossed by equally fine spiral lirae, giving this portion of shell a finely decussated appearance under an ordinary lens; on upper portion of base there are two narrow grooves not widely separated, and another lower down. Sutures superficial, covered with enamel. Aperture oblique, high, rounded, angled and canaliculate above and below, convex on lower, concave on upper inner side. Base truncate and deeply notched. Outer lip sub-vertical, only slightly curved, thin and sharp; base rounded, with two minute projections at junction of upper basal groove. Inner lip not broadly calloused below but widening out on upper portion and extending well on to spire. Base of columella a little recurved, with a broad open canal, neck obliquely plicated, with a solid callus pad at extremity. Fasciole broad and flat, separated from inner lip by a groove, shallow at the extremities but deepening in middle. Colour crystalline white with apex of spire light orange-chrome, sutures with narrow bands of almost pure white. In the type the dorsal portion of shell appears to be stained with iron oxide, but the paratypes do not show any trace of colour except at apex. Operculum thin, horny, transparent, tinged with yellow in centre, elongate, nucleus subapical, faintly sculptured with fine subcircular growth-lines, with a few prominent ones more distantly placed. There are also two distinct ridges beginning towards apex, inner one short, outer one a little lower, and continuing parallel with the outer margin round base; there is also a subcentral area somewhat thickened, with irregular markings.

Diameter, 5.1 mm.; height, 11.6 mm. (type—large specimen): 4.4 × 9.9 mm., 4 × 8.9 mm. (paratypes). Angle of spire, 64°.

Animal unknown.

Holotype and several paratypes in author's collection.

Habitat.—Russell, Bay of Islands (A. E. B.).

Situation: Dredged in 3–5 fathoms, bottom of fat mud.

Three specimens were obtained alive and three dead; the dead specimens are chalky, without the coloured apex. In general outline this species resembles A. mucronata Sow.

Laevilitorina Pfeffer, 1886, Jahr. Anst. Hamburg, vol. 3, p. 81.

Laevilitorina iredalei n. sp. (Plate 102, fig. 3.)

Shell small, elongate, obliquely conical, light-horn-coloured, shining beneath the coating of dirty brown. Epidermis thin, dull, easily removed. Sculpture consists of microscopic growth-lines only. Whorls 4 ½, rather rapidly increasing, the last larger than all the others taken together, outlines convex. Sutures impressed, margined. Protoconch of about 1 ¼ turns, roundly flattened. Spire a little higher than aperture. Base rounded. Aperture broadly obliquely ovate, subangled above. Peristome continuous,

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outer edge thin, inner margin thickened. Columella oblique, rounded, same colour as shell. Inner lip with thin callus. Umbilicus represented by a chink. Operculum horny, thin, transparent, with numerous transverse curved striae, crossed by longitidunal irregular curved fine ridges; nucleus submarginal, of about 2 turns, and nearer the base.

Diameter (major), 1.5 mm.; height, 2 mm. Angle of spire, about 70°.

Animal unknown.

Holotype and several paratypes in author's collection.

Habitat.—Near Russell, Bay of Islands (A. E. B.).

Situation: Under loose boulders, partly embedded in sand.

I have very much pleasure in naming this small shell in honour of Mr. T. Iredale, for kind assistance rendered at various times. This species is not common: only about a dozen specimens were obtained after several days' collecting on a stretch of coast half a mile long.

Arca Linné, 1758, Syst. Nat., vol. 10, p. 693.

Arca sociella n. sp. (Plate 102, figs. 4, 4a.)

Shell very small, subrhomboidal, equivalve, inequilateral, costate. Anterior and posterior slopes rounded. Ligament long, narrow, extending well behind beaks. Umbones prominent, beaks a little incurved, well separated and situated about anterior fourth. Anterior end short, obliquely rounded, posterior end larger; dorsal margin angled behind, winged; posterior margin obliquely descending, produced; anterior margin with a few crenulations, and posterior broadly crenulated within, extending a short distance along ventral margins; basal margins straight, ventral irregularly rounded. Sculpture consisting of radiating rounded costae, more distant anteriorly, crossed by close concentric narrow well-defined striae, which produce, especially on posterior portion, a bold nodulous sculpture. Colour light yellow-brown, interior pale cream, shining. Hinge-plate moderately wide, narrower in middle, and curved. Teeth small, oblique, situated on either side of beaks, slightly curved, not at all distinct. Adductor-scars unequal, anterior pyriform, posterior ovate and larger. Pallial line simple. Dorsal area from beaks towards the posterior margins rather deeply excavated on either side, being broadly rounded, leaving dorso-posterior margins of valves arcuate.

Length, 5 mm.; height, 2.2 mm.

Holotype and paratypes in author's collection.

Habitat.—Near Russell, Bay of Islands (A. E. B.); type: Doubtless Bay (A. E. B.): Great Barrier Island (A. B. W. Powell).

Situation: Living in small colonies attached to boulders partly embedded in sand.

In sculpture this shell resembles A. metella Hedley. from Tasmania, but the contour of the two species differs considerably.