VERTEBRATA. 



253 



PERISSODACTYLA. Toes one or three, encased in hoofs, or, if 

 four-toed, then the toe smaller and not touching the ground. 

 Stomach simple ; caecum large and sacculated. 



The living species of this suborder " are widely removed from 

 one another in many important characters ; but the intervals 

 between them are largely filled up by an extensive series of fossil 

 forms, commencing in the Lower Tertiary strata." A large 

 number have been recently discovered in North America (in 

 Utah, Colorado, Kansas, Oregon, &c.), and have been worked out 

 principally by Marsh and Leidy. 



In regard to the extinct forms of Equidae, Eohippus and Oro- 

 hippus were Eocene, Miohippus and Anchitherium Miocene, and 

 Hipparion, Protohippus, and Pliohippus Pliocene. Dinocerata 

 ( = Uintatheriidae) and Pantodontia (Bathmodon, &c.) constitute 

 the Amblypoda of Cope. 



Of the Rhinoceroses one form (R. tichorhinus) was once common 

 in Europe. 



*Bathmodon. 



The systematic position of the following group is very doubtful. 

 It comprises certain very large extinct mammals from the 

 Pleistocene deposits of South America, having affinities with 

 the Rodentia, Bruta, and Ungulata. It forma the order Tozo- 

 dontia of Owen. 



TOXODONTIA. 



* Nesodon. 



* Toxodon. 



