River, and the forks of the Cheyenne River. From these beds over three hundred species of 

 vertebrates have been reported, and the most of these are mammals. The Tertiary has been 

 justly called the ' age of mammals,' for prior to this period the mammals were not larger than 

 a mouse. The mammals are found in a great variety those of elephantine size, and, with 

 them, those that were no larger than an ox, and on down to the size of a rabbit. These Ter- 

 tiary fields have, from a scientific standpoint, yielded fossils of greater importance to the 

 anatomist and paleontologist than the Jurassic. Here are found the first horses, and from the 

 Wyoming beds nearly a complete series has been obtained. Many of the fossils found in the 

 Green River and Big Horn basins are not known to any other locality. Some of these are so 

 rare that there has been only a single specimen found. Nearly all of these animals bear a 

 scientific name only, but there are representatives of such animals as rhinoceroses, camels, 

 deer, wolves, cats, beavers, and monkeys. Among the most remarkable might be mentioned 

 the following : 



" Anaptomorphus, Tomitherium, Mesonyx, Bathyopsis, Coryphodon, Phenacodus, Uin- 

 tatherium, Hyrachyus, Palaeosyops, Hyaenodon, Nimravus, Hyracodon, Titanotherium, 

 Elotherium, Oreodon, and Aceratherium. 



" The mammals were not the only life. Many of the fresh-water lakes during the period 

 were swarming with fishes, turtles, and crocodiles, all of which are found in great abundance. 

 The fossil fish found in the Green River shales are the most perfect specimens known. The 

 largest are so beautiful that a single fish has sold for $100, and choice specimens are held for 

 higher prices. Associated with the fishes are numerous fossil insects that are also rare 

 specimens and highly valued by scientific collectors. The turtles and crocodiles are in great 

 variety and are found in so many bands that they are the common fossils of the lower 



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