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UNGULATA 



Suborder PERISSODACTYLA 



This is a perfectly well-defined group of Ungulate mammals, 

 represented in the actual fauna of the world by only three distinct 

 types or families the Tapirs, the Rhinoceroses, and the Horses 

 poor in genera and species, and (except in the case of the two 

 domesticated species of Equus, which have been largely multiplied 

 and diffused by man's agency) not generally numerous in individuals, 

 though widely scattered over the earth's surface. Palseontological 



ABC 



FIG. 151. Bones of right fore foot of existing Perissodactyles. A, Tapir (Tapirus indicus), 

 X I ; B, Rhinoceros (Rhinoceros sumatrensis), x t ; C, Horse (Equus caballus), x J. U, ulna ; 

 R, radius ; c, cuneiform ; I, lunar ; s, scaphoid ; u, unciform ; m, magnum ; td, trapezoid ; tm 

 trapezium. From Flower, Osteology of Mammalia. 



records, however, show very clearly that these are but the surviving 

 remnants of a very extensive and much -varied assemblage of 

 animals, which flourished upon the earth through the Tertiary 

 geological period, and which, if it could be reconstructed in its 

 entirety, would not only show members filling up structurally the 

 intervals between the existing apparently isolated forms, but would 

 also show several marked lines of specialisation which have become 

 extinct without leaving any direct successors. 



The following are the principal characters distinguishing them 

 from the Artiodactyla. Premolar and molar teeth in continuous 

 series, with massive, quadrate, transversely ridged or complex 

 crowns, the posterior premolars often resembling the true molars 



