VERTEBRATA: MAMMALIA. 695 



Artiodactyla, to which the name of Teleodactyla might be 

 applied. 



Fam. 2. Rhinocerotidce. This family comprises only a single 

 living genus, the genus Rhinoceros, unless, indeed, the little 

 Hyrax is to be retained in this order. The Rhinoceroses are 

 extremely large and bulky brutes, having a very thick skin, which 

 is usually thrown into deep folds. The muzzle is rounded 



and blunt, and there are ?-h? grinders, with tuberculate crowns. 

 7 7 



The typical dental formula is 



,=2 ; /*|4=4. 3n3 Ora8 . 



o o' 44 33 



There are no canines ; and the incisors are often wanting in 

 the adult (as in the living two-horned species), or may be in- 

 creased in number (as in the extinct Accrothcrium}. The 

 crowns of the praemolars and molars (fig. 390) exhibit two 

 principal tracts of dentine, not filled up by cement. 



Fig. 390. Teeth of the upper jaw of Rhinoceros Indiciis^ (after Cuvier). wz 1 , m z Molars ; 

 /;!, pnfi Prsemolars ; i Incisor. 



The skull (fig. 391, B) is pyramidal, and the nasal bones are 

 generally enormously developed. The nasal bones usually 

 support one or two horns, which are not paired in any living 

 form. The horn is composed of longitudinal fibres, which are 

 agglutinated together, and are of the nature of epidermic 

 growths, somewhat analogous to hairs. When two horns are 

 present, the hinder one is carried by the frontal bones, and is 

 placed in the middle line of the head behind the anterior horn. 

 The posterior horn is usually much shorter than the anterior 

 one; and if not, it differs in shape. In the extinct genus 

 Diceratherium of Marsh, from the Miocene of Oregon, there 

 are two horns placed transversely and symmetrically upon the 



