VALVATA. At 
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 that 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 tricariata. 
[14] 
