THE IOWAN ICE INVASION 353 



Terrace deposits two miles from the mouth of Sinsinawa River and two 

 and a half miles west of Galena, Illinois, contain a fauna of molluscan land 

 shells. This may be the same deposit as that referred to by McGee, Chamber- 

 lin, and others. Trowbridge and Shaw 28a say of this deposit: "So far as our 

 region is concerned the deposition of the loess may have accompanied or fol- 

 lowed the Iowan, Illinoian, or even perhaps the Kansan ice epochs, or a part of 

 it may have been deposited during or after each one. " It is probable that loess 

 was deposited during each interglacial interval and that these deposits represent 

 an accumulation of all or most of the glacial stages and intervals. As a char- 

 acteristic Peorian mollusk {Pyramidula shimekii) occurs in the deposit the 

 shells recorded may perhaps be considered as having been buried during the 

 Peorian interval. 29 Ten species are recorded, two of which (starred) are 

 figured: 



Pyramidula shimekii* Sphyradium edentulum alticola 



Vallania costata Euconulus fulvus 



Pupilla muscorum Succinea campeslris \= grosvenori?) 



Pupilla decora Succinea avara* 



Bifidaria cf. corticaria Lymnaea parva 



b. Vertebrate fauna 



In the southern part of the Driftless Area a vertebrate fauna occurs in 

 the crevices of the limestone, and in the clay immediately overlying the lime- 

 stone, which seems referable to the Peorian interval, tho some of it may be 

 of later date. In Illinois the crevices are 40 feet beneath the surface. These 

 deposits are near Galena, Illinois, Dubuque, Iowa, and in Grant and Richland 

 counties, Wisconsin. The reason for including the lead region fauna in the 

 Peorian interglacial interval is its geological position, in crevices of the indigi- 

 nous bed rock covered by clay and loess. 



Hay 29a refers the vertebrates of the driftless area to post- Wisconsin time 

 but the inference is strongly in favor of their being post-Iowan or Peorian, 

 since the region is largely covered with Iowan loess, beneath which many of 

 the bones have been found. There seems no good reason for considering the 

 majority of the finds of later date. 



Jeffries Wyman, 30 Joseph Leidy, 31 and John LeConte 32 record the following 

 species, nearly all of which have been found near Galena, Illinois. 



*»• Bull. 26, EL GeoL Surv., p. 106. 



» Galena-Elizabeth Folio, U. S. G. S., No. 200, p. 7. 



»» GeoL Iowa, XXIII, pp. 38, 487. 



" GeoL Wis., I, pp. 421-423, 1863. 



■ Op. cii., p. 424. 



* Amer. Joum. Sci., (iii), V, pp. 103-106. 



