GEOLOGICAL PAPERS. 113 



gravels. The evidence offered by the study of the canal section 

 seems to point to the conclusion that the post-Glenwood and pre- 

 Calumet interpretation is correct, since the whole history of 

 Wilmette Bay corroborates it. The strata near Evanston which 

 underlie the Rose Hill Bar contain no evidences of life (excepting 

 the remains of wood) and probably represent a land surface 

 (Goldthwait, Bull. 7, 111. Geol. Surv., p. 65) bordering a swamp. 



It has been stated by several writers' that at the time of the 

 post-Glenwood deposits a climate and flora existed similar to that 

 of Alaska. The presence of the spruce (Picca cvanstoni or cana- 

 densis), which does not now grow within about one hundred 

 miles, seems to afford ample evidence of a colder climate. 



The presence of Unio crassidens in the Upper Tolleston deposits 

 is of great interest. This has been thought^ to indicate a warmer 

 climate than now prevails, especially in view of the fact that the 

 species has also been found in deposits near Green Bay.^ It may 

 be. however, that this is a case in which the mollusk was not able 

 to adapt itself to a new environment and so became extinct bO 

 far as these regions are concerned. The Green Bay fauna evi- 

 dently followed the Wisconsin River-Lake Xicolet route. The 

 northern limit of this species at present is as follows : 



South of 



Green Bay 



Record. 



Wisconsin, between Prairie du Chien and De Soto" 80 miles 



^linnesota, not recorded. 



Iowa, Lansingr" 80 miles 



Michigan, not recorded. 



Illinois. Utica, La Salle County^" 220 miles 



Ohio, Scioto River'^ .' 260 miles 



Indiana, Tippecanoe River" 230 miles 



Of the other species represented in this deposit, all are now 



living in the Chicago area excepting Amnicola Ictsoni,'^^ which 



was first discovered in the gravel deposits of Goat Island. Niagara 



Falls. ^"^ Onadnila coccinca is also quite different from the usual 



form as found in northern Illinois and appears to be the same as 



the variety paupcrcnla of Simpson. As the species enumerated as 



having been found in the Upper Tolleston deposit also live as 



^For example, Higley and Raddin, Bull. Chi. Acad. Sci., II, Xo. 1, p. XIV. 



^Science, n. s., XXXI, p. 716. 



BWagner, Xautilus, XVIII, pp. 97-100, 1905. 



loChadwick, Bull. Wis. Nat. Hist. Soc, IV, p. 95, 1906. 



"Museum record. 



I'Baker, Bull. 111. State Lab. N. H., VII, p. 77, 1906. 



i^Sterki, Proc. Ohio Acad. Sci., IV, p. 392, 1907. 



"Daniels, 27th An. Rep. Dept. Geol. Ind., p. 650, 1902. 



i^Bull. Buf. Soc. X. Sci., VII, Xo. 1, p. 241, fig. 165. 



^^This species has since been found living bj- Mr. Bryant Walker. 



