Page:Journal of the Academy of Natural Sciences of Philadelphia (IA journalofacademy01acaduoft).pdf/24

14 rior base of the tentacula; base or foot of the animal dilated, oval, obtuse before and behind.

Found under stones, &c. in moist situations, on the margins of rivers. Like those of the genera Lymnæa and Planorbis this animal possesses the faculty of crawling on the surface of the water, in a reversed position, the shell downward.

Shells subovate, oblong or somewhat tapering. Aperture entire, longitudinally oblong, the right lip circularly joined to the left at the base and folded back on the pillar.

L. columella. Shell thin, fragile, horn-colour; whorls four, longitudinally wrinkled. Spire prominent, acute. Suture not much impressed. Aperture dilate, ovate. Columella much narrowed near the base, so that the view may be extended from the base almost to the interior apex of the shell. Length seven-tenths of an inch nearly; of the spire one-quarter of an inch.

Inhabits stagnant waters and miry places.

Collection of the Academy.

Animal aquatic, base not so long as the aperture; dusky, with small whitish spots, tentacula broad, pyramidal, compressed; eyes small, black, placed at the inner base of the tentacula.

This species is allied to L. Catascopium of the American edition of Nicholson's Encyclopedia, but the revolution of the whorls is more oblique, the shell thinner, the aperture much more dilated, and the columella differently