The placement of the species in either Anatoma or Thieleella, distinguished by protoconch sculpture, could not be resolved from Numanami & Okutani's (1990) original description, because no SEM images of the protoconch were provided. We examined the holotype by SEM, showing flocculant protoconch sculpture, which confirms its placement in Anatoma.
The body of the wet preserved holotype of Anatoma shiraseae was removed by DLG almost completely except for the very tip of the visceral mass.The uncoated shell was imaged by variable pressure SEM. The animal had distinctly recognizable eggs. The paratype shell had been coated for SEM by the original authors, but was partially broken prior to examination by SEM (K. Hasegawa, pers. comm.). The pieces show the diagnostic keel on the shoulder of the shell, but the protoconch is missing from the remains.

Diagnosis: Shell large, biconical, with a prominent spiral ridge on shoulder, and denselly cancellate sculpture.
Description:
Shell large (up to 4.2 mm in diameter), biconical . Protoconch of 1 1/8 whorls, 244 µm in diameter in the holotype, with flocculant sculpture, rounded margin, and no apertural varix. Teleoconch I of 3/4 whorls, sculptured with low axial ribs, two spiral cords in position of selenizone. Teleoconch II of up to 2 1/4 whorls. Shoulder with many fine axials, approximately 95 on last whorl, intersected by approximately 21 radials of same strength, producing cancellate pattern. Shoulder with distinct, broad spiral ridge. Base with similar spiral ridge below selenizone. Base with approximately 115 fine axials, 29 somewhat stronger spirals threads. Umbilicus wide, open, sloping continuously with base. Parietal portion of aperture slightly flared; no funiculus. Aperture subquadratic. Selenizone at periphery with fragile distended keels. Slit open, margins constricting anteriorly. Operculum corneous, multispiral, slightly smaller than aperture. Animal unknown.

Type Locality
Gunnerus Bank, Antarctica [68°23.5'S, 24°07.5'E], 281-282 m (OD).