204 Natural History Bulletin. 



Stenotrcma leaii, (Ward) Binn. Not common. Fossils from 

 Polk county, Iowa, and Saunders county, Nebraska, closely 

 resemble recent specimens from Iowa, Illinois and Nebraska. 



This form is at present found from Ohio to Nebraska, and 

 north to Michigan. 



Mesodon umltiliiicata, (Say) Try. Not uncommon. Fossils 

 from Johnson county, Iowa, and Cuming and Saunders 

 counties, Nebraska, are much smaller than the ordinary form 

 of this species which is commonly found on river bottoms, but 

 in size and in the heavier shell they very closely approach 

 specimens from Johnson, Hardin, and Pottawattamie counties, 

 Iowa, which were collected in the vicinity of prairie swamps. 



Vallonia pitlckclla, {IslneWcC) 'Q'lnn. Quite common. Fossils 

 from Johnson and Muscatine counties, Iowa, and Cuming, 

 Lancaster, and Saunders counties, Nebraska were compared 

 with recent specimens from Nevada, Montana, Dakota, Iowa, 

 Minnesota, Indiana, Ohio, New York, and Vermont. The 

 fossils are somewhat larger than than the majority of the 

 recent specimens which were examined, being equalled only 

 by those from Montana and Nevada (in both cases from high 

 altitudes). There is some variation in both the recent and 

 fossil shells, but the averages are as above stated. This form 

 is the typical V. pulchdla. The smaller var. costata was not 

 found in the Loess. 



Fernssacia subcylindrica, (L.) Binn. Not very common- 

 Fossils from Johnson county, Iowa, and Lancaster county, 

 Nebraska were compared with recent specimens from Mon- 

 tana, Nebraska, Iowa, Ohio, New York, and Canada. There 

 is but little variation in the size and form of both the recent 

 and fossil shells, and the latter are not distinguishable from 

 the former except by the bleached appearance peculiar to the 

 Loess fossils. This species is now found from Nebraska to 

 New York, and northward, and is common to Europe, Asia, 

 and North America. 



