KEEWATIN AND LAURENTIDE ICE-SHEETS 537 



Lake and Lake Superior lobes of the Laurentide ice-sheet extended to western 

 Minnesota, and the latter lobe was deflected southward into Iowa. This ice does 

 not appear to have retreated beyond the limits of Minnesota., and was followed 

 by a comparatively short interglacial period. 



During the third invasion, the Wisconsin, the Minnesota lobe of the Keewatin 

 ice-sheet advanced from the northwest across central Minnesota into Iowa. At 

 the same time the lobes from the Laurentide ice-sheet advanced southwestward 

 until, in several localities, they reached the northeastern limit of the Minnesota 

 lobe. The final retreat of the three lobes was contemporaneous, forming glacial 

 lakes and numerous moraines. A new mapping of the moraines in Minnesota is 

 presented in support of the views advanced. The Rainy Lake lobe was divided 

 into the Red Lake and Leech Lake lobes; the Lake Superior lobe was divided 

 into the Mille Lacs and Saint Croix lobes, and the Minnesota lobe sent a promi- 

 nent lobe, the Chisago lobe, northeastward to the Saint Croix river. 



DE VON I A N INTER VA L IN MISSO URI 

 BY C. R. KEYES 



This paper is printed as pages 267-292 of this volume. 



DEVONIAN FISH FAUNA OF IOWA 

 BY C. R. EASTMAN 



[Abstract] 



During the last four decades important collections of fossil fish remains from 

 the Middle and Upper Devonian of Iowa have been brought together by Messrs 

 O. Saint John, C. A. White, Samuel Calvin and his assistants on the Iowa Geological 

 Survey, C. L. Webster, and others. The greater part of these collections being 

 now deposited in the Museum of Comparative Zoology at Cambridge, exceptional 

 facilities have been enjoyed for investigating the structure and variations of the 

 species represented and for studying the assemblage as a whole in its relations to 

 other faunas. In particular, the Upper Devonian "state quarry fish-bed" discov- 

 ered by Professor Calvin has yielded rich material for study, the results of which 

 are embodied in this paper. The most general conclusion that can be drawn is 

 that the Hamilton piscine fauna of Wisconsin, Iowa, and Illinois is so closely 

 related to the Corniferous of Ohio and New York as to stamp it as merely a later 

 and western phase of the former, the two together corresponding to the Middle 

 Devonian fish fauna of the Eifel, Bohemia, and Russia. Migrations from the 

 Canadian province on the east do not seem to have taken place until the Chemung 

 epoch, with which the peculiar faunas of the state quarry and Sweetland Creek 

 beds appear to be contemporaneous. 



FORMER EXTENT OF THE NEWARK SYSTEM 

 BY W. FT.. HOBBS 



This paper is printed as pages 139-148 of this volume. 



