Shell small, thin, of four whorls, of a dull amber yellow without a darker streak behind the outer lip; apex rounded, rather blunt, surface polished with occasional incremental irregularities and a microscopic spiral striation obsolete in places; spire shorter than the aperture, the last whorl much the largest, the suture not deep, the whorls moderately rounded; outer lip sharp, inner lip slightly erased and whitened; pillar straight, thickened where it meets the body, with a little depression behind it. Length 8; length of aperture 5; max. diameter 5 mm.

Alaska. Ponds near Bernard harbour, rare.

This is remarkable as the most northern species known of the genus. By some unexplained factor, perhaps connected with glaciation, the genus Physa is not represented in the boreal region of Asia or America between the western Siberian boundary and cape Bathurst. It occurs in southern Siberia among the headwaters of the Amur river. In America the most northerly localities reported are Moose Factory on Hudson bay, and Great Slave lake. The allied genus Aplexa seems to take the place of Physa in all the boreal region above referred to. When we consider that the large Lymnaeas of the type of L. stagnalis and Aplexa hypnorum, abound to the very verge of the Polar sea, it seems difficult to account for the absence of Physa, elsewhere associated with them.