ANCYLUS RIVULARIS. 



Variety. A. brunneus. Flatter, narrower 

 behind, posterior slope less concave. 



Hab. James river, Virginia, at Buchanan. 



OBSERVATIONS. 



Larger, and rather more elongate than A. 

 tardus and depressus, and having the apex 

 rather more posterior. Dr. Gould's figure 153 

 agrees very nearly with this species, but his 

 description (p. 224) appears to belong to A. 

 parallelus, as the elongate A. fluviatilis of 

 Europe is noted as an alhed species. 



