BODY greyish-white, rather transparent: tube short, sub-conical, obliquely truncate at its orifice: foot broad at its base, abruptly pointed, and very extensible: mantle bordered with grey.
SHELL subtriangular, rather ventricose and solid, glossy, strongly grooved concentrically, horn-colour or yellowish-grey: epidermis rather thick : anterior side abruptly truncate : posterior side much produced, and sloping towards the lower margin, which is obliquely curved; leaks rather prominent, but obtuse : ligament short, conspicuous : inside bluish-white and nacreous : hinge strong and curved ; teeth arranged as in Sphaerium, but the lateral teeth in this and other species of Pisidium are exceedingly strong and developed in proportion to the size of their shells: muscular and pallial scars well marked. L. 0,3. B. 0,375. Varieties occur in which the striae are more numerous, fewer, stronger or fainter than usual.
HABITAT : Slow rivers, lakes, canals, and streams in all parts of the kingdom. It is also one of our commonest upper tertiary fossils. Its continental range ex¬tends from Siberia to Naples, and it is also found in Algeria. This is the largest kind of Pisidium.