CONCHOLOGIA CESTRICA. 83 



tubercles, at the outer bases of the tentacles; verge 

 small, simple, lunate. 



S. altilis, LEA. 



Melania altilis, Lea, Proc. Amer. Phila. Soct, s. niuus. 



TT [W. G.B.] 



" 



Fig, 176. 



Shell, smooth, sub-globose, thick, pale horn 

 color; spire short; whorls 4, obtusely angular 

 above; aperture large, nearly round, white. 

 H. 8, W. 6, mill. 



Lingual Dentition of S. altilis, witJi the rachidian tooth greatly 

 enlarged. [Stimp.] 



Fig, 177, 



Station, Delaware and Susquehanna Rivers; abundant. 



Family STREPOMATID^E. 



Shell, elongate-conical, or turbinate ; peristome not 

 entire. 



Animal, rostrum long; foot oval; tentacles subulate; 

 eyes at their external bases ; margin of the mantle not 

 digitate ; opercle corneous, semi-concentric, or pauci- 

 spiral ; oviparous. ' 



Genus GONIOBASIS, LEA, 1862. 



Shell, thick, elongate-conical ; aperture sub-rhomboid, 

 higher than wide ; columella not twisted ; base sub- 

 angular, without a channel. 



