902 HISTORICAL GEOLOGY. 



American Turtles, from the Lower Miocene, or Wliite River beds, of Dakota, 

 Testudo hrontops of Marsh, wliich had a length of about two and two thirds 

 feet. The Puerco beds have afforded a species of Champsoscmrus (C. Sapo- 

 oiensis of Cope), a Laramie genus. A very small species of Crocodile has 

 been reported from the White River beds. 



3. Birds. — The Eocene and Miocene have afforded remains of species 

 related to Waders, an Owl, Bubo leptosteiis of Marsh, a bird near the 

 Woodpeckers, some web-footed species allied to the Gannet; and the Mio- 

 cene, remains of a large Eagle, a Cormorant, and other birds. The Diatryma 

 gigantea of Cope, from the early Eocene of Xew Mexico, was larger than the 

 Ostrich. The Barornis regens of Marsh, from the Upper marl beds of 

 Squankum, N". J., of the Eocene, had about the size and many of the charac- 

 ters of the Ostrich. From the Florissant beds have been obtained a Plover 

 and other species. 



4. Mammals. — The sea-border Tertiary of the continent has afforded 

 remains of but few Mammals ; for seashores are not their ordinary resort 

 except for aquatic kinds. The regions of the great lakes over the Rocky 

 Mountain area, on the contrary, have been found to be literally Tertiary 

 burial-grounds. They bear evidence that Mammals in great numbers, and 

 of several successions of faunas, lived and died about these lakes, and by 

 lacustrine agencies were buried. 



These ancient bone-beds remained almost unknown to science until the 

 year 1847 ; and now, through the labors of explorers, and the works of 

 Leidy, followed by the memoirs of Marsh, Cope, Scott, Osborn, and others, 

 the number of known species far exceeds that of existing North American 

 Mammals. These Mammals are, with rare exceptions, of the ordinary or 

 placental type. The Marsupials, as in earlier time, were small species, re- 

 lated to the Opossums ; and their remains are known from the Early Eocene 

 onward. 



Eocene. — The Eocene species comprise Herbivorous, or Ungulate, Car- 

 nivorous, Insectivorous, and Rodent species, and also Quadrumana; and 

 before the close of the period. Cetaceans, or Whales. The remains of Ungu- 

 lates are most abundant, because such species frequent lake borders. They 

 are related to the modern Tapir, Wild Boar, and Rhinoceros, yet only in 

 a very general way, as these special types belong to a later period. The 

 earliest of the Eocene species are remarkable for their prototype or primi- 

 tive characteristics : (a) the legs being approximately equal ; (6) the feet 

 five-toed and of typical form, the five toes similar, with the third or middle 

 toe a little the longest ; (c) the carpal bones and the tarsal in vertical series 

 with the following bones of the foot; {d) the teeth of the typical number, 

 44, — that is, 11 in either ramus of each jaw, — the 11 including 3 incisors, 

 1 canine, 4 premolars, and 3 molars ; (e) the molars of simple form, being 

 usually tritubercular at summit, or trigonodont; (/) the head without 

 armature of horns or tusks. 



