198 NATURAL HISTORY BULLETIN. 



and northwestern Iowa, and thence westward, where it 

 lives in high, dry situations. Its easternmost known 

 station in Iowa is in Winnebago county. 



**SUCCINEA GROSVENORII Lea . (?) 



A form referable to this species is quite common in the 

 local loess. The species now lives abundantly in the South, 

 and in Nebraska and western Iowa, and is uniformly found 

 (so far as the writer's experience shows) in situations 

 which are exposed to severe drouth during at least a portion 

 of each year. 



The Succineas of this group, both recent and fossil, 

 require further elaboration. 



It is interesting to note that the foregoing species, now 

 extinct at Iowa City, all belong to the modern terrestrial 

 fauna of the dry west, from Montana to New Mexico, and 

 that only two species extend eastward as far as Iowa. 



2. Terrestrial species, now living at Iowa Citv. 



a. Species of higher, more or less exposed, and 

 often rocky slopes. 



*Vallonia parvula Sterki. 



Common on exposed rocky slopes, hence occuring in 

 scattered colonies. Rare in the loess of western Iowa. 



*Leucocheila fallax (Say) Try. 



Locally common on higher exposed slopes, chiefly under 

 fragments of limestone. Rare in the loess of western Iowa 

 and eastern Nebraska. 



**Bifidaria armifera (Say) Sterki. 



Very common. Most frequent on more or less exposed 

 slopes under limestone, among roots of grasses, etc. 

 Sometimes also in deeper shade, and occasionally on lower 



