As Turtonia occidentalis Dall, 1871
Shell subtrigonal, slightly inequilateral, small and smooth. Color purplish ; lighter, with a yellowish epidermis, toward the margin, especially anteriorly. Interior dark purple in the middle of the valves, margins lighter, dark brown above and behind. Hinge-line and ventral margin roundly arcuate, ends rounded, anterior a little shorter and smaller. Epidermis yellowish brown, polished, with rather strong lines of growth at intervals. Umbones rather prominent, usually eroded. Shell a little tumid. Teeth strong, apparently three cardinals in the left valve, with the posterior dorsal hinge margin folded in making a strong tooth-like lamella. Right valve with one long and one triangular cardinal tooth, and a posterior lamella as in the other. Pallia! line simple, lightly waved near the posterior muscular scar. Anterior scars two, perfectly separate and distinct, the upper triangular, slightly smaller.
Lon. 0,2. Alt. 0,16. Diam. 0,1 inch.
Habitat. Plover Ray, Eastern Siberia, abundant in the roots of fuci. Dall., 1865 and 1866.