On a New Species of Epitonium.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 55, 1924, Page 138

On a New Species of Epitonium. By A. W. B. Powell. [Read before the Auckland Institute, 14th December, 1922; received by Editor, 28th December, 1922; issued separately, 26th May. 1924.] Plate 5. While collecting specimens of Epitonium jukesianum, philippinarum, and zelebori at Mount Maunganui, Bay of Plenty, Dr. Bucknill noticed another species that was quite distinct. Suter mentions in the Manual of the New Zealand Mollusca that a white variety of Epitonium tenellum is sometimes found. No doubt this species is the one referred to, but a closer examination reveals the presence of microscopic spiral striations and various points of difference from the other species of the genus. Epitonium zelebori also possesses spiral sculpture, but belongs to the section “Cirsotrema Moerch,” characterized by the distinct spiral keel, prominent spiral ribs, and denticulate axial ribs, so cannot be confused with this new example, which is a true Epitonium. A few weeks after the discovery of the species at Mount Maunganui Mr. La Roche, of Auckland, found seven specimens of the shell at Whangaroa. That a shell of this size had escaped notice so long, and was then found in two widely separated localities almost simultaneously, is remarkable, and serves to show that there is still much to be accomplished before the knowledge of our molluscan fauna nears completion. The author has great pleasure in uniting with the species the name of its discoverer. Thanks are also due to Mr. La Roche for his invaluable assistance. Epitonium bucknilli n. sp. Shell of moderate size, semitransparent, imperforate, thin and fragile. Sculpture consists of arcuate lamellar axial ribs, discontinuous over the whorls, 16 to 20 on last whorl. The type has 20 ribs on last whorl; interstices with microscopic spiral striations. Colour pure white. Spire elevated, conic, about 2½ times the height of aperture; outlines straight. Protoconch small, of 2 smooth convex whorls. Whorls 7, convex, a little separated, not shouldered; base convex. Suture deep. Aperture oblique oval. Peristome continuous, thickened by an axial rib, very slightly expanded at base. Columella short, oblique, slightly arcuate. Inner lip slightly rounded with free and sharp margin. Operculum unknown. Diameter, 7 mm.; height, 16.5 mm.; angle of spire, 30° (type). Average specimen: Diameter, 5 mm.; height, 11.5 mm. Animal unknown. Habitat: Mount Maunganui, Bay of Plenty; Taupo Bay, Whangaroa; Kaitoke, Great Barrier Island. Material: The holotype in the author's collection, Auckland. Six para-types were obtained at Mount Maunganui, twenty specimens at Whangaroa, and one at Great Barrier Island.

Epitonium bucknilli n. sp. 7 mm. × 16.5 mm.