202 LIFE OF THE PLEISTOCENE 



ben southwestward into the Mississippi River. A preglacial Rome River 

 is thot to have flowed thru Oneida Lake, and Black River flowed northward 

 into the St. Lawrence. Rivers in the Cayuga, Seneca, and Genesee valleys 

 are believed to have flowed northward into the St. Lawrence River. 



Investigations by Leverett 17 and other glaciologists indicate that some pre- 

 glacial streams, especially in southern Michigan and northeastern Illinois, 

 had a southerly direction and flowed into the Gulf of Mexico. Whatever the 

 direction of the drainage of this region may have been does not materially 

 affect the established fact that the Great Lakes were once river valleys and 

 that they, together with the buried river channels, formed avenues by which 

 the preglacial biota spread over the country. 



2. Preglacial Life of the Glaciated Area 



In the preceding pages it has been shown that previous to the advent of 

 the Glacial Period, the physiography of the country was quite mature and that 

 large river systems occupied extensive river valleys. If the physical features 

 were of such maturity, it follows, obviously, that the biota was equally mature. 

 Unfortunately the data bearing upon this point is of the most meagre character, 

 as only a very small portion of the surface was left intact by the first ice inva- 

 sion, and the diversity of the biota can be judged only by the life contained in 

 deposits laid down beyond the limits of glaciation or in the first interglacial 

 deposits of the Aftonian stage. 



Among the mammals the sloths, Megalonyx, Mylodon, and Megatherium, 

 several species of the horse, Equus, members of the cat and dog families, the 

 hornless rhinoceros, the tapir, the peccary, numerous species of deer, rodents, 

 some of gigantic size and the proboscidians, the mastodon and mammoths, 

 roamed over the country in great numbers. Of invertebrates, little is definitely 

 known, tho it is believed that the molluscan fauna differed but little from that 

 of today. The insect fauna is said by Scudder to be composed largely of 

 extinct species. 



According to Penhallow, 18 a forest of great denseness extended far into 

 the Arctic regions, consisting of such species as beech, sycamore, tulip tree, 

 oak, sweet gum, walnut, magnolia, and many others. A temperate climate, 

 very much warmer than now and somewhat subtropical, extended to the 

 northern boundary of the United States, as shown by fossil plants about the 

 Arctic regions. An Arctic bog flora^must have existed north of this great 

 forest, in polar lands. 



Data concerning the life immediately preceding the first glacial invasion 

 are rare and meagre. Some remains of life found in caves not far removed 

 from the border of the ice have been thot to be preglacial, but the exact age 



17 Mich. Acad. Sri., 12th An. Rep., p. 22, 1910. 

 " Trans. Roy. Soc. Can., X, pp. 56-74, 1904. 





