Occasional Papers of the Museum of Zoology ii 



Zonitoidcs numuius Van. 



Vitrea indentata (Say). 



Strobilops labyriiitJiica tcxasiana Pils. 



Bifidaria contracta (Say). 



Bifidaria cristata P. & V. 



Bifidaria hordeacella Pils. 



Bifidaria pcntodon (Say). 



Bifidaria tappaniana (C. B. Ads.). 



Vertigo decora (Gld.). 



Physa forsheyi Lea. 



Planorhis Icntns Say var.? Nearly all of the larger 

 Planorbcs collected by Dr. Case have the strongly 

 sculptured inner whorls with raised revolving lines, 

 giving a tresselated effect, which appears to be char- 

 acteristic of the southern form that has been received 

 both as lentns and tumid us. This sculpture is usually 

 very strongly developed for about the first three or 

 four whorls, after which the spiral lines become 

 obsolete. The longitudinal sculpture is more per- 

 sistent, but varies greatly at maturity. There is also 

 great variation in shape accordingly as the shell is 

 compactly or loosely coiled. This form, which is 

 widely distributed through the western states from 

 South Dakota to Texas, is quite different from typi- 

 cal tutnidus. It seldom attains the size of what 

 Crosse and Fischer regard as typical lentus from 

 New Orleans, but, as stated, agrees better with that 

 in its sculpture than with the typical northern triz'ol- 

 vis, to which it is often referred. 



25. Sand flats on the east bank of the Cimmaron River, west 

 in a straight line from Alva, Oklahoma. 

 Succinea grosvernori Lea. 



