424 ORDERS OF MAMMALIA. 



SECTION A. PERISSODACTYLA. The section of the Perisso- 

 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, 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. 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 removed 

 from one another in many important characters ; but the inter- 

 vals 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. 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 



H H 



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 enor- 

 mously 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 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. 



The fossil species of Rhinoceros are numerous, commencing 

 in the Miocene Tertiary, and ranging through the Pliocene 

 and Post-Pliocene deposits. The species of Rhinoceros may 

 be divided into groups, as follows : 



i. Those in which the nostrils are separated by a bony sep- 



