474 ZOOLOGY SECT. 



In the Perissodactyles 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 (Equidse) have the distal divisions of the limbs slender, 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 aggre- 

 gation of slender fibre-like elements. The eyes are small, the 

 auditory pinnae well developed. The surface is devoid, or nearly 

 devoid, of hairs, and the skin is enormously thick, and in some 

 species thrown into deep folds. The tail is narrow and of moderate 

 length. 



The Hyraxes are small, somewhat Rabbit-like animals, with 

 slender limbs and vestigial tail. There are four functional digits 

 in the manus and three in the pes, all provided with short flat 

 nails, except the innermost of the pes, which has a curved claw. 

 The body is covered with soft fur. 



The Elephants, the largest of existing terrestrial Mammals, have 

 the limbs much more typically developed than in the true Ungu- 

 lates, there being five comparatively short digits, enclosed in a 

 common integument, in each foot, all of them in the fore- and 

 three or four in the hind-foot terminating in a broad flat nail. 

 The limbs are very stout and pillar-like, and the thigh and leg, 

 when at rest, are in a straight line instead of being, as in the 

 Ungulata vera, placed nearly at right angles to one another a 

 circumstance which gives a characteristic appearance to the 

 hind-quarters. The nasal region is produced into a proboscis or 

 ' trunk," a mobile cylindrical appendage, longer than the rest 

 of the head, at the extremity of which the nostrils are situated. 

 There is in the male a pair of immense tusks the incisors of 



