694 



MANUAL OF ZOOLOGY. 



Horse and its allies, and some extinct forms, all agreeing in 

 the following characters : 



The hind-feet are odd-toed in all (fig. 388, B), and the fore-feet 

 in all except the Tapirs and Brontotheridce. The dorso-lumbar 

 vertebra are never less than twenty-two in number. The femur 

 has a third trochanter. The horns, if present, are not paired 

 (except in the extinct genus Diceratherium, and in the family of 

 the Brontotheridce). Usually there is only one horn, but if there 

 are two, these are placed in the middle line of the head, one behind 

 the other (fig. 392). In neither case are the horns ever supported 

 by bony horn-cores. The stomach is simple, and is not divided 

 into several compartments ; and there is a large and capacious 

 ccecum. 



The three existing groups of Perissodactyle Ungulates 



namely, the Horses, Tapirs, 

 and Rhinoceroses 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. 



The section of the Perisso- 

 dactyle Ungulates includes the 

 following seven families : 



Fam. i. Coryphodontidce. 

 This family comprises only a 

 (Mter number of extinct Tapir-like 

 animals, belonging to the Eo- 

 cene period. The skull is of the Perissodactyle type, hornless, 

 with small nasal bones. The brain is remarkably small, and 

 the dentition is complete, the dental formula being 



33 i i 4-4 33 



The canines are not excessively developed, and the molars are 

 of the Tapiroid type, having two transverse crests or ridges. 

 The limbs are short, and both the fore-feet (fig. 389) and the 

 hind-feet are furnished with five complete toes, all of which 

 carried hoofs. The genus Coryphodon is the principal or only 

 one comprised in the family; and as it contains the only 

 Ungulates with the complete number of five digits on each 

 foot, it might with propriety be raised to the rank of a distinct 

 section, equal with the sections of the Perissodactyla and 



