Genus Myadora Gray, 1840.
Type: Pandora brevis Sowerby.

Myadora delta n. sp. (Figs. 19, 20.)

Shell rather small, subtriangular; beaks slightly behind middle; apical angle about 100°. Left valve concave, with relatively strong posterior twist. Anterior dorsal margin straight, descending at about 45° to narrowly rounded anterior margin. Posterior dorsal margin flatly sigmoid, merging into obliquely truncated posterior margin. Ventral margin widely arcuate. Lunule and escutcheon narrow, flat, extending full length of dorsal margins. Sculpture of low, broad, concentric ridges, obsolete over most of disc, but strong along anterior dorsal margin. Lithodesma narrowly triangular. Anterior and posterior margins of shell raised and grooved along whole length. Adductor-scars noticeably distant from umbo and near ventral