VALVATA. 41 



3. VALVATA HUMERALIS, Say. 

 Hald., p. 9. Plate 16, fig. 3. 



Shell subdiscoidal, spire convex, not much 

 elevated ; volutions three and a half, with 

 plane shoulders. Aperture rounded, umbilicus 

 moderate. Color light green. 



Diam. 4, alt. 2-75 mill. 



Mexico. 



I figure and describe this species from the 

 single type specimen in the museum of the 

 Academy of Natural Sciences. The plane 

 shoulder has the appearance of being a mon- 

 strosity. It has been surmised that this spe- 

 cies is identical with my Valvata virens, but 

 until more specimens are obtained no satisfac- 

 tory conclusion can be arrived at. It is cer- 

 tain that Mr. Say's description will not apply 

 to my species unless it is understood tliat the 

 plane upper surface of the whorls is only the 

 result of abnormal growth. The shell appears 

 to me to differ much more from virens than it 

 does from tricarinata. 



[14] 



