532 MANUAL OF ZOOLOGY SECT. 



In the Hippopotami the body is of great bulk, the limbs 

 very short and thick, the head enormous, with a transversely 

 expanded snout, prominent eyes, and small pinnae. The 

 tail is short and laterally compressed. The toes are four in 

 each manus and pes, all reaching the ground. The surface 

 is naked, with only a few hairs in certain positions ; the skin 

 is of great thickness. 



In the sub-order Perissodactyla (Horses, Tapirs, Rhino- 

 ceroses) the third digit is either the only complete one in both 

 fore- and hind-foot (Horses) or there are only three digits 

 (second, third, and fourth) in each (Rhinoceroses), or there 

 are four in the fore-foot and three in the hind (Tapirs). 

 The Horses, Zebras and Asses (Equidae) have the distal 

 divisions of the limbs slender, the metacarpals and meta- 

 tarsals nearly vertical to the surface of the ground, and 

 the single hoof massive and with a broad lower surface. 

 Though the head is elongated, the nasal region is not 

 produced into a proboscis. The tail is short or moderately 

 long, and is either beset throughout with a large number 

 of very long coarse hairs, or with a tuft of such specially 

 developed hairs at the extremity. A mane of similar large 

 hairs usually runs along the dorsal surface of the neck. 

 There is a wart- like callosity above the wrist, and in the true 

 Horses a second a little below the heel or " hock." 



The Tapirs have the body more massive than the Horses, 

 and the limbs, especially the distal segments, shorter and 

 stouter. The nasal region is produced into a short proboscis. 

 The surface is beset with a scanty covering of hairs. The tail 

 is vestigial. 



In the Rhinoceroses the body is extremely massive, the 

 limbs short and stout, and each digit is provided with a hoof- 

 like nail. There is a short soft muzzle. Either one or two 

 remarkable median horns are borne on the nasal region, not 



