502 ZOOLOGY sect. 



subsequently becoming firmly fixed. Between them is a short, 

 rounded, median bony protuberance on the frontal region of the 

 skull. The antlers of the Deer, which, except in the case of the 

 Reindeer, are restricted to the male sex, are bony growths covered 

 only while immature by a layer of skin, the " velvet," provided with 

 very soft, short fur. Antlers are shed annually, and renewed by 

 the growth of fresh vascular bony tissue from the summit of 

 a pair of short processes of the frontal bones, the iJCcUdes. Even- 

 tually when the antlers are full grown, a ring-like thickening of 

 the bone — the "burr"' — appears round the base of the antler, and 

 constricts the blood-vessels, so *hat the substance of the antler 

 becomes converted into dry, dead bone; the skin shrivels and 

 is peeled off. The antler is shed by the absorption of the bone 

 immediately beneath the burr. The pinnae of the ear of tlie 

 Ruminants are well-developed. The tail is sometimes elongated, 

 and provided with a terminal leash of long coarse hairs; sometimes 

 short and bushy. The entire surface, with the exception of the 

 end of the muzzle, which is naked, is always covered with a close 

 coat of longer or shorter hairs. 



In the Pigs the legs are relatively short, and the two lateral 

 toes of both manus and pes are fully developed, though scarcely 

 reaching the ground. The surface is covered with a scanty coat 

 of coarse bristles. There is a truncate, mobile snout, the anterior 

 end of which is disc-shaped and free from hairs. The pinnte are 

 large; the tail is rather long, narrow and cylindrical, provided 

 with a terminal tuft of strong hairs. A remarkable feature of the 

 males is the development of the canine teeth of both jaws into 

 large, -upwardly-curved tusks. In the Peccaries, which resemble 

 the Pigs in most of the features mentioned, the points of the 

 upper tusks are directed downwards. 



In the Hippopotami (Fig. 1117, Im), the body is of great 

 bulk, the limbs very short and thick, the head enormous, with a 

 transversely expanded snout, prominent eyes, and small pinnaj. 

 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 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 " {Equidce, Fig. HIS) 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 Avith a large number of very 



