634 TEXTBOOK OF ZOOLOGY 



Order Prohoscidea. — This small order includes only two genera 

 of elephants with one species each of the largest terrestrial animals. 

 One species, Elephas indicus, is Asiatic, and the other, Loxodonta 

 africana, lives in the tropical forests of Africa. Both have the nose 

 extended several feet as a muscular trunk or proboscis which is a 

 very handy and useful appendage. The skull is very thick, with air 

 spaces, and the molar teeth are very large, with prominent ridges. 



Order Sirenia. — This is a very limited order of sea-cows. They are 

 aquatic mammals with a pair of flexible anterior flippers and a strong, 

 rounded tail. The dugongs of the Indian Ocean and Australia, and 

 the Manatees of the Atlantic Ocean represent the group. The Florida 

 manatee, Trichechus latirostris is only rarely found. 



Order Odontoceti (The Toothed Whales). — All of the whales are 

 mammals which have become adapted to a strictly aquatic life. The 

 body is modified for swimming by the reduction of appendages, the 

 horizontal flattening of the tail and its division into two lobes or 

 "flukes." The head of these animals is large with long jaw bones. 

 The nostrils open by a single aperture from which the breath is 

 spouted when the animal comes to the surface. A thick layer of fat 

 or "blubber' is deposited beneath the skin and this serves to conserve 

 heat in the body. The porpoise, Phocaena pJwcaena, is very common 

 in the Gulf of Mexico and elsewhere. It is about six feet long and 

 rolls around in the water. It catches such fish as mackerel and 

 squeteague for food. The sperm whale, Physeter catodon, is a large 

 whale of about seventy-five feet in length. Such other animals as 

 the beaked whale, dolphin, and narwhal belong in this order. The 

 killer whale, Orcinus orca, is generally distributed. It is about 

 twenty feet long, ferocious and predatory on fish, seals, and even 

 other whales. 



Order Mystacoceti. — This is the whalebone whale group. Their 

 teeth do not develop beyond the embryonic stage, but they are re- 

 placed by cordlike plates of baleen or whalebone. Whalebone was 

 once an important item of commerce, being used in making whips, 

 stays, and other flexible articles. The largest species in the order 

 and, in fact, the largest of all animals is the sulphur-bottom whale, 

 Sihhaldus musculus. It reaches a length of one hundred feet and 

 lives in the Atlantic and in the Pacific off the coasts of Central 

 America, Mexico, and California. The gray whale, Bhachianectes 

 glaucus, is another Pacific form. The Greenland right whale, 



