454 ZOOLOGY 



and a fifth, where now there is no trace of either. The horse 

 has been domesticated as long as we have records and there are 

 as many breeds of horses as we found of chickens, some half a 

 hundred. The ass and zebra belong to the same genus, Equus. 

 They both cross with the horse. Tapirs are included in this 

 suborder. 



Suborder (c) Proboscidea (with proboscis). Two living and 

 many extinct species of huge Placentalia with five digits, each 

 with a distinct hoof. The nose is much developed into a pre- 

 hensile organ, with corresponding changes in the skull for at- 

 tachment of muscles. The skin is thick and loose. The upper 

 incisors grow enormously, forming the tusks characteristic of 

 the group. There are no canines; molars are very complex. 

 The two teats are thoracic. The largest of the land mammals, 

 the elephants and the extinct mastodon and mammoth, belong 

 here. They are now confined to the tropical regions of Asia 

 and Africa, though in geological times they seem to have had a 

 world- wide range. The tusks of species of elephants, both living 

 and extinct, furnish the ivory of commerce. 



Order 6. Carnivora (flesh-eaters). The Garni vora are four- 

 or five-toed animals with the digits ending in claws. The 

 canines are well developed, strong and curved. The other teeth 

 are often pointed and adapted to holding or tearing. Muscles 

 of mastication are especially well developed. Mammas are 

 numerous, occurring along the entire abdomen. There are two 

 types of Carnivora terrestrial and marine. To the first belong 

 the bear family, which is perhaps the least specialized group; the 

 dog family, including dogs, wolves, foxes, jackals; the cat family, 

 including lions, tigers, leopards; hyenas; many fur-bearing ani- 

 mals as otters, weasels, minks, martens, badgers, wolverines, 

 and skunks. There are more than forty species of these fur- 

 bearing animals in North America. The seals and walruses 

 belong to the marine group. In these forms the appendages 

 have become adapted to the water habit, the digits bearing 

 intervening webs. 



The principal American cats are: the wild cat (also called 

 bob cat and catamount), Canada lynx, the cougar (also called 

 puma, panther and mountain lion), and the jaguar of Mexico 



