582 MANUAL OF ZOOLOGY. 



the Perissodactyla, in which the toes or hoofs are odd in num- 

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

 even in number (two or four). 



SECTION A. PERISSODACTYLA. The section of the Peris so- 

 dactyle Ungulates includes the Rhinoceros, the Tapirs, the 

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

 the following characters : 



The hind-feet are odd-toed in all (fig. 249, 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. 250). 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. 



Fam. i. Rhinoceridcz. 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 



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



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

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

 enormously developed. The feet are furnished with three toes 

 each, encased in hoofs. The nasal bones usually support one 

 or two horns, which are not paired. 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. 

 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- 



