LIMNJSAD^E. 243 



verse striae, and all of them obscurely striate lon- 

 gitudinally ; aperture narrow oval, not a third part 

 as long as the spire, with the pillar spread and white, 

 but not forming an umbilicus, 



It varies in the convexity of the volutions, and 

 their number, as we have them from different waters 

 with from six to nine. 



This animal, like the other species, but perhaps 

 more frequently, forms a thick white internal rib to 

 the outer lip, just within the edge. 



Mr. Jeffreys (Linn. Trans, xvi. 178.) placed in 

 this genus Assiminia Grayana, a Ptenobranchous Mol- 

 lusc, and Helix detrita> which is an exotic terrestrial 

 species. 



2. AMPHIPEPLEA Nilson. (Membrane Shell.) 



The animal very like LimnceuS) but the edge of the 

 mantle is lobed and produced, so as to cover 

 (when the animal is expanded) the oval, very thin, 

 nearly membranaceous, flexible shell, which, like 

 Limnaus, has a plait on the pillar lip ; its axis and 

 part of the body whorl is covered with an expan- 

 sion of the inner lip. 



Miiller, Montagu, and Nilson, give a good de- 

 scription of this animal. Draparnaud considered the 

 part of the mantle which is reflected over the shell 

 to be a viscid coat. 



Captain Brown, apparently not aware of the prior 

 name, has called this genus Lutea, a name that is 

 quite inadmissible. 



94. 1. AMPHIPEPLEA glutinosa. Glutinous Membrane 

 Shell, (t. 9. f. 103.) Shell semiglobular, ex- 

 M 2 



