Eatoniella fossa

Eatoniella fossa is a species of marine gastropod mollusc in the family Eatoniellidae.^[1] First described by Winston Ponder in 1965, it is endemic to New Zealand, found in waters off the northeastern coast of the North Island, the Hen and Chicken Islands, Manawatāwhi / Three Kings Islands, and the sea banks that surround Manawatāwhi.

In the original description, Ponder described the species as follows:

Shell of medium size for [the subgenus Dardanula], solid, smooth, shining, ovate-conic, a groove between inner-lip and body whorl, Spire rather tall, very slightly convex; whorls 41⁄2, faintly convex, smooth and polished; protoconch smooth, small; sutures distinctly false margined; body whorl with a rounded periphery and base. Aperture small, rounded, slightly angled posteriorly, with a deep groove between inner lip and body whorl. Peristome continuous, thickened, especially in posterior corner; outer lip thickened) internally, with a sharp edge, hardly excavated. Colour of dead shells varies from brownish-yellow to white, a band below the sutures may be darker or lighter than rest of shell; aperture and umbilical region white. A few irregular zig-zag markings sometimes developed on last part of body whorl from a peripherial dark band or small dark blotches. The dark subsutural band, if present, may break up into irregular blotches on the body whorl. Holotype yellowish-white with a few faint brown blotches on last part of body whorl and a large reddish-brown blotch just behind aperture.^[2]

E. fossa measures 1.9 mm (0.075 in) by 1.2 mm (0.047 in).^[3] It can be distinguished from other members of Eatoniella due to the channel between the aperture and the body whorl.^[2] The species is superficially similar in appearance to Anabathron.^[4]

The species was first described by Winston Ponder in 1965, who used the name Eatoniella (Dardanula) fossa.^[2] The modern formatting of the name without a subgenus, Eatoniella fossa, was established by Hamish Spencer and Richard C. Willan in 1995.^[5][6] The holotype of the species was collected by K. Hipkins on 29 December 1953 at a depth of 40 m (130 ft) off the west coast of Stephenson Island in the Whangaroa Harbour, Northland. It is held by the Auckland War Memorial Museum.^[7][8]

The species is endemic to New Zealand, found off the northeastern coast of the North Island, as far east as Hicks Bay,^[9][10][3] as well as the Hen and Chicken Islands,^[11] Manawatāwhi / Three Kings Islands, and the Middlesex and King banks off the coast of Manawatāwhi / Three Kings Islands.^[3] The species lives between a depth of 0–622 m (0–2,041 ft) below sea level.^[3]