THE 0\^RLAND KOUTE — -COUNCIL BLUFFS TO OGDEN, 



9 



The Aftonian gravels separate two glacial deposits known as till, 

 consisting of sandy clay in which are fragments of rock ranging from 

 grains of sand to bowlders 2 feet or more in diameter. These frag- 

 ments are of limestone, sandstone, quartz, and other rocks, but the 

 largest and most conspicuous are of quartzite and granite, including 



arctic species foUoAved the retreating ice 

 front nortliward, and their place "u^as 

 taken "by animals adapted to life in a 

 temperate climate. 



One of the effects of the climatic 

 changes and the resulting migration of 

 animals was a radical change of fauna. 

 Could one of the Pleistocene men return 

 and view the present-day animals they 

 would seem as strange to him as those of 

 an African jungle are to an inhabitant of 

 the Great Plains. Prof. W. B. Scott, in 

 his history of land mammalsj says of 

 the Pleistocene fauna: 



*'It is probable that the Pleistocene fos- 

 sils already obtained give us a fairly ade- 

 quate conception of tlie larger and more 

 conspicuous mammals of the time but no 

 doubt represent very incompletely the 

 small and fragile forms. With all its gaps, 

 however, the record is A'ery impressive. 

 * * * The fossils have been gathered 

 over a very large area, extending from 

 ocean to ocean and from Alaska to Central 

 America. Thus their wide geographical 

 range represents nearly all parts of the 

 continent and gives us information con- 

 cerning the mammals of the forests a-s well 

 as of the plains. 



"Those divisions of the early and mid- 

 dle Pleistocene which enjoyed milder 

 climatic conditions had an assemblage of 

 mammals, which from one point of view 

 seems very modern, for most of the f^-enera 

 and even many of the species which now 

 inhabit North America date back to that 



;eogr: 



:his 



it contains so many animals now utterly 

 foreign to North America, to find near rela- 

 tives of which we should have to go to 

 Asia or South America. Some of these 

 animals which now seem so exotic, such 

 as the llamas, cameb, and horses, were yet 

 truly indigenous and were derived from a 

 long line of ancestors which dwelt in this 

 continent but are now scattprprl nl^ri,v»a 



was 



and are extinct in their original home, 

 while others were migrants that for some 

 unknown reason failed to maintain them- 

 selves. Others again are everjwhere ex- 

 tinct. 



''Most surprising, perhaps, in a North 

 American landscape is the presence of the 

 Proboscidea, of which two very distinct 

 kinds, the mastodons and the true ele- 

 phants, are found together. Over nearly 

 the whole of the United States and south- 

 ern Canada, and even with sporadic occur- 

 rence in Alaska, ranged the American 

 mastodon {Mastodon americanus), which 



in the plains but verj' abundant 

 in the forested regions, where it persisted 

 till a very late period and was probably 

 known to the early Indians. This ani- 

 mal, while nearly related to the true ele- 

 phants, was yet quite dilTerent from them 

 in appearance. * * * The tusks were 

 elephant-Uke, except that in the male 

 there was a single small tusk in the lower 

 jaw, which can not have been visible ex- 

 ternally; this is a remnant of an earlier 

 stage of development, when there were 

 two large tusks in the lower as well as the 

 upper jaw. The creature was covered 

 with long, coarse dun-colored hair; such 

 hair has been found with some of the 

 skeletons. 



*'0f true elephants, the North Ameri- 

 can Pleistocene had three species. Most 

 interesting of these is the northern or 

 Siberian mammoth {Ekphas primigenius), 

 a late immigrant from northern Asia, 

 which came -in by way of Alaska, where 

 Bering Land (as we may call the raised 

 bed of Bering Sea) connected it with Asia. 

 The mammoth was abundant in Alaska, 

 British Columbia, and all across the 

 northern United States to the Atlantic 

 coast. Hardly any fossil mammal is eo 

 well known as this, for the carcas^a en- 

 tombed in the frozen gravels of northern 

 Siberia have preser\'ed every detail of 

 structure. It is thus definitely known 



