2-3 mm

Habitat: it seems it prefers detrital-muddy bottoms of the deep circalittoral zone. Distribution: it can be found in a large part of the Mediterranean, even in remarkable depths.
Notes: shell oblique in outline, pyriform, stretched and roundish anteriorly, inequilateral, a little bit inequivalve, wider in its left valve. All that can be noticed near umbo and lunule. Umbo small and protuberant. Posterior margin sharp-cornered at the crossing with the ventral margin. In the posterior area it is present one obsolete furrow originating one small auricle. Lunule well defined, a little bit embedded. There are some prominent ridges on the margins and this is a detail present in this species only. Surface crossed by light concentric striae. The ferrugineous deposit is confined to the anterior and posterior dorsal zones. T. obsoleta (Verril & Bush. 1898) is similar in outline to succisa but more roundish and it does not present the typical plicae near lunule. During the several growth stages there are not noticed strong variations in outline, also the premature individuals have the posterior margin truncated. Auricle protuberant.
As far as this species is concerned, Payne & Allen (1991) described a subspecies, atlantica, which is not quoted by CLEMAM. The adult specimens average measures are around 2 mm in length.