172 THE ILLINOIS GLACIAL LOBE. 



5. Pyramidula perspective (Say) Pils. 

 G. Yallouia pulchella (Mull.) Biuu. 1 



7. Cocblicopa lubrica (Miill.) P. & J. 



8. Leucbochila fallax (Say) Try. 



9. Pupa muscorum L. 



10. Bifidaria corticaria (Say) St. 



11. Bifidaria armifera (Say) St. 



12. Bifidaria pentodon (Say) St. 



13. Sphyradium edentulum alticola (luger.) P. & J. 



14. Succinea avara Say. 



15. Succinea obliqua Say. 



16. Succinea luteola Old. 



17. Succinea grosveuorii Lea. 

 IS. Heliciua occulta Say. 



19. Limnaea humilis Say. 



Of these species all but the last one are strictly terrestrial in habit, 

 One species, No. 5, rare in northern loess, is very common in the loess of 

 Mississippi. The last species, No. 19, is an aquatic pulmonate, occurring- in 

 pockets or restricted parts of the loess as though deposited at the edge of 

 a pool or pond. 2 As for the last five species in List IV this may be said: 

 They are strictly fluviatile. There are reasons for believing, however, that 

 they did not come from unmodified loess, 3 and morever they and their 

 relatives have thus far not been found in any other locality except in what 

 is clearly modified loess. There still remain lists VI and VIII which will 

 be discussed separately. 



The fossils of List VI are in all probability from alluvium, and not 

 from the loess, for two reasons — one positive, the other negative: 



1. The list very closely resembles lists of species found in alluvium 

 along several streams, notably along Rock River near its mouth, along the 

 Cedar River at Cedar Rapids and near Mount Vernon, and along the Iowa 

 near Iowa City. 4 It will be observed that the species in this list are 

 grouped according to habit. The first section or group contains the terres- 

 trial forms, nearly all of which also occur in the loess. All row live on 

 alluvial bottom lands or the adjacent hills, and their shells are often washed 

 down for short distances. 



2. The list in its entirety is unlike any undoubted loess fauna which 

 has been reported by trustworthy observers. 



1 See footnote a on ]). 169. 



2 See discussion of Limna-a by Sliirnek, in Proc. Iowa Acad. Sci., Vol. V, 1898, pp. 3-1, 35. 



3 Professor Shimek reached this conclusion after a conversation with Professor Witter. 

 ■•The Rock River list was published in Iowa University Bulletiu, Vol. II, pp. 170 and 171. 



