UNGULATA. 553 



ber (one or three), and the Ariiodadyla, in which the toes are 

 even in number (two or four). 



Section A. Perissodactyla. — The section of the Perisso- 

 dactyle \3vi%\i\3X.t% includes the Rhinoceros, the Tapirs, the 

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

 the following characters : — 



The hind-feet are odd-toed in all (fig. 215, A, D), and the 

 fore-feet in all except the Tapirs. The dorso-lumbar vertebrae 

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

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

 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. 216). 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 

 caecum. 



The three existing genera of Perissodactyle Ungulates — 

 namely, the Horse, Tapir, and Rhinoceros — are widely re- 

 moved from one another in many important characters ; but 

 the intervals between them are filled up by an extensive series 

 of fossil forms, commencing in the Lower Tertiary Strata. 



Fain I. Rhinoceridce. — This family comprises only a single 

 genus, the genus Rhinoceros, unless, indeed, the little Hyrax 

 is to be retained in this order. The Rhinoceroses are ex- 

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

 is usually thrown into deep folds. The muzzle is rounded 



7" — 7 

 and blunt, and there are molars, with tuberculate crowns. 



7 — 7 

 There are no canines, but there are usually incisor teeth in 

 both jaws. The skull is pyramidal, and the nasal bones are 

 enormously developed. Thg feet are furnished with three toes 

 each, encased in hoofs. The nasal bones support one or two 

 horns, which are not paired. The horn is composed of longi- 

 tudinal 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. 

 The Rhinoceroses live in marshy places, and subsist chiefly on 

 the foliage of trees. They are exclusively confined at the pre- 

 sent day to the warmer parts of the Old World ; but an extinct 

 species (^Rhinoceros tichorhinus^ formerly inhabited England, 

 and ranged over the greater part of Europe. Of the one- 

 horned species, the best known is the Indian Rhinoceros (^R. 



