Thyasira oblonga: Habitat: it lives in the deep circalittoral zone, on slimy bottoms.
Distribution: it can be found in a large part of the Mediterranean but never common.
Notes: shell brittle, small in sizes, equivalve, inequilateral, oval in outline. Typical posterior margin: non grooved but dorsally inclined, making with ventral margin one subacute angle. Anterior and ventral margins are roundish in form, umbo rather prominent from dorsal margin, from which it protrudes anteriorly. Valves rather convex. During the different growth stages, this species does not change its outline very much. It can be mistaken with its similar one T subovata from which it is distinguishable, besides its different outline, also due to the presence of a fine denticulation on dorsal margins. Allen (in litt.) admits this species can be conspecific with T pygmaea (Verril & Bush, 1898). Thyasira carrozae Payne & Allen, 1991 is quoted by CLEMAM dubitatively as synonym of T. oblonga. The average measures are around 2 mm in width. (See confrontation table page 142).