264. APPENDIX. 



PHYSA. 



P. heterostropha, nob. North-west Territory. 



VALVATA. 



V. sincera. Shell subglobose-conic ; whorls nearly four, 

 accurately rounded, finely and regularly wrinkled across ; 

 aperture not interrupted by the penultimate whorl nor 

 appressed to it, but merely in contact with it, the labrum 

 not diminished in thickness at the point of contact; urn- 

 bilicus large, exhibiting the volutions. 



Breadth less than one-fifth of an inch. 



Inhabits North-west Territory. 



For this species I am indebted to Dr. Bigsby. It is very 

 similar to the tricarinata, nobis, but is destitute of cari- 

 nated lines, and the umbilicus is rather larger; it differs 

 from the obtusa of Europe, also, in the much greater mag- 

 nitude of the umbilicus. PL 15, fig. 11. 



PALUDINA. 



P. limosa^ nob. North-west Territory. 



AMPULARIA. 



A. depressa. Shell ventricose, subglobular, obsoletely 

 banded with obscure green ; whorls four, slightly wrinkled ; 

 body whorl more prominent above, somewhat flattened to- 

 wards the suture, of a pale olivaceous colour, which is al- 

 most concealed by numerous, unequal, longitudinal and 

 transverse greenish and brownish lines ; spire very much 

 depressed : aperture suboval, within somewhat glaucous, 



