GASTEROPODA. 



191 



in some species reflected on the shell*; foot broadly lan- 

 ceolate, or subovate ; tongue armed with many transverse 

 rows of numerous stout uuciuated teeth, with furcated 

 hooks, flanking a minute, simple, hooked, central denticle, f 

 — 52 species: also fossil. 



This genus was united with Physa, as the shells are 

 similar in most respects, differing chiefly in the direction 

 of their spires,, and also in the oblique plait on the colu- 

 mella : but they are separated now. as the annuals are 

 found to differ. They are abundantly found in our rivers 

 and ponds (particularly the latter, as they appear to prefer 

 stagnant water), and in other parts of Europe. Africa, and 

 America : one or two species have been mentioned as 

 natives of India. They feed on aquatic plants, coming to 

 the surface of the water for air ; the eggs, which are in 

 great numbers, are deposited on stones, and the stems and 

 leaves of vegetables, in long masses enveloped in a glairy 

 substance. Darwin mentions finding LymnecE in great 

 numbers in a lake near Rio de Janeiro, into which the 

 inhabitants assured him the sea annually, and sometimes 

 oftener, entered, and made the water quite salt. 



There are nine British species. Beck arranges the 

 fifty-two species under four genera: — Oinphiseola Rqfin. : 

 Linmophysa Fitz. ; Limna?a and Gulnaria Leach. 



Amphipeplea. Nilson. — Shell thinner than 

 that of the last genus, more delicate, ahnost 

 globular, with very short spire, and very wide 

 aperture. Animal, differing from that of Lymn&a 



* Philippi places those that have the mantle retleeted over the 

 shell in the next genus, 

 t Forbes's British Moll. 



