366 BRANCH CHORDATA 



age of six. The females mature younger. The males ure six or eight times 

 as large as the females. The rivalry between the males is intense. In the 

 fighting, great strength of neck and jaw is used. The fur seal industry rep- 

 resents many millions of dollars.' 



The walrus family {Trichcr/i'idce) belongs to the aquatic carnivores. The 

 walrus is arctic and circumpolar. It is characterized by the enormous 

 canines of the upper jaw, which form tusks sometimes 30 inches long. The 

 walrus is from 10 to 12 feet long, and, though it can move about on land, it 

 is very ungainly. The hair is short and scanty. As in the true seals, there 

 are no external ears. The flesh, fat, and hide are much used in the North. 



The true seals {Pho'cidw) have the nostrils in a dorsal position and have 

 no external ears. The hind limbs are bound up with the tail and are useless 

 on land. The largest is the elephant seal, about 20 feet long. The male 

 has a proboscis of about 1.5 inches. This seal is mild and inoffensi\c except 

 when enraged, and, of course, during the breeding season. The whole 

 animal is invested in a mass of blubber which is as thick as that in a whale. 



Order IX. Insectiv'ora. — These are small, plantigrade, long- 

 snoutctl, chiefly nocturnal mammals, which feed on insects and 

 earthworms. The eyes are small or hidden by fur. The clav- 

 icle is usually present; the cecum, absent or minute. As a rule, 

 there are five digits. All of this order are provided -ndth sharp 

 teeth. The front teeth in both jaws are inclined outward, being 

 less adapted for seizing the prey. The brain is of simple struc- 

 ture, the hemispheres usually smooth. 



Hedgehogs are covered with spines, but they are not barbed as in the 

 porcupine, and they are firmly attached. Hedgehogs feed upon insects, 

 chickens, young game birds, and even vipers. They are less than a foot in 

 length, about the size of a big rat. They disap])car in hot weather, and come 

 out in rainy weather. They hibernate in winter. E. europtpiis defends it- 

 self by rolling up into a ball, with its head tucked between its fore feet and 

 the hind feet drawn up close together, thus presenting, on all sides, its sharp 

 spines to its enemies, few of which will attack the hedgehog. Hedgehogs 

 are not found in the \\'estcrn Hemisphere. Their voice is described as a 

 sound between a grunt and a squeak. 



The shrews (Horic'idoe) (Fig. 293) are small, nocturnal, fur-coveied in- 

 sectivores, which are often mistaken for mice, but the teeth show they are 

 not rodents. They are of wide distribution, but. are not found in .Australia 

 nor in South America. .Several species are found in the United States. 

 S. per^omilus is chestnut brown, with large ears and short tail. They are 

 thinly covered with hair. Their length is 2 J inches; the tail, 1 inch. They 

 are found from Massachusetts to Alaska. The water shrew (S. palus(ris) 

 is the largest of our shrews, measuring 6 inches, with the tail 2^ inches long. 

 The lesser shrews of Great Britain are burrowing, nocturnal animals, and 

 secrete a disagreeable odor for protection. They are among the smallest 

 of all mammals. 



' See Hornaday, or Jordan's "Report of the Fur Seal Investigation," 

 1896-97. 



