538 MANUAL OF ZOOLOGY SECT. 



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, rhinoce- 

 roses) 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 (Equidce) have the distal divisions of the limbs slen- 

 der, the metacarpals and metatarsals nearly vertical to the 

 surface of the ground, 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, each digit 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 

 attached directly to the skull ; these are epidermal structures 

 which are formed of a dense aggregation of slender fibre- 



