AMPHIPEPLEA. 255 



Sub-gen. omphiscola, Rafinesque (Leptolimnea, Swains.). 



Shell nearly cylindrical ; spire thick, lengthened ; aperture 

 small. 



glabra, Milll. pugio, Beck. 



Sub-gen. acella, Haldeman. 



Shell very slender ; whorls 4-6, flattened, oblique, suture dis- 

 tinct; aperture entire, produced, expanded, without fold. 



gracilis, Jay. 



Genus AMPHIPEPLEA, Nilsson. 



Tentacles flattened and triangular. Mantle-margin form- 

 ing an extended lobe, reflexed and partially covering the 

 shell. 



Shell hyaline, thin, globosely ventricose ; spire short, 

 depressed ; aperture wide ; inner lip expanded over the last 

 whorl ; outer lip simple, acute. 



Si/n. Lutea, Brown. Myxus, Leach. Mixus, Say. 



Ex. A. Leuconensis, Eydoux and, Souleyet, pi. 83, fig. 

 8. Shell, A. glutinosa, Miiller, fig. 8, a. 



According to Mr. William Thompson, the tubercle of the 

 lateral teeth in Amphipeplea is very large in proportion to 

 its plate. The even-edged, lobate mantle enveloping the 

 shell is the obvious distinguishing characteristic of this 

 genus, which differs from Physa in the triangular form of 

 the tentacles, and in the dextral shell. The animals crawl 

 slowly, and appear to prefer tranquil waters and muddy 

 localities. Species have been found in the Islands of the 

 Philippine Archipelago, and the ponds of Europe also 



