Chap. 37 MAMMALS AND MANKIND 763 



and walruses. When a sea lion is hungry it sinks to the sea bottom, usually in 

 the shallows, stands on its head and grubs up clams and sea snails with its 

 tusks. 



Perissodactyla (Fig. 37.14). Horse, ass, zebra, tapir, and rhinoceros are 

 all perissodactyls (odd-toed). Animals in this and the next two orders have 

 hoofs. Formerly, they were included in one order Ungulata (hoofed) but are 

 now believed to be less closely related than their feet would suggest. All hoofed 



Fig. 37.12. Mink {Putorius vison) . The mink, about the size of a slender cat, 

 is a crafty killer of muskrats, ducks, chickens and fishes, seldom hunting far from 

 a lake or stream. Its fur is soft and the glistening guard hairs have long captured 

 human eyes and pocketbooks. (Courtesy, Rand: The Chordates. Philadelphia, The 

 Blakiston Co., 1950.) 



animals are herbivores. In members of this group, the main weight falls upon 

 the tip of the third digit. In horses, it is the only one that touches the ground; 

 the second and fourth are splint bones attached to it (Fig. 38.6). Tapirs have 

 four digits (thumb lacking) on the front feet and three on the hind ones. The 

 snout of the tapir is an example of similar ones in the elephant, proboscis 

 monkey, and others, that show convergent evolution. Tapirs are natives of Cen- 

 tral and South America and Malaysia. 



Artiodactyla (Fig. 37.15). Pigs, peccaries, hippopotamuses, and cud- 

 chewers such as camels, deer, giraffes, cattle, sheep and goats, chamois, and 

 others are all even-toed. Their weight is carried by the third and fourth digits 

 which are equally developed. The teeth are usually of the plant-feeding type. 



Proboscidea. Elephants are the most highly specialized of living mammals 

 (Fig. 37.16). With its trunk, an elephant can lift logs, dehcately examine the 

 texture of a leaf, pick up a peanut, suck up a drink of water and pour it into 

 the mouth, or give itself a shower bath (Fig. 5.3). An elephant bears its weight 

 on all five toes of each foot. They are bound together with connective tissue 

 so that the sole is a large hooflike expanse. The teeth are exceptional in that 

 one pair of upper incisors becomes the tusks and there are no canines.. The 

 development of the cheek teeth is peculiar and slow; finally, they acquire great 



