162 MANUAL OF ANIMAL BIOLOGY 



fur which is frequently of considerable commercial value. The 

 Carnivora are clearly divided into the terrestrial forms, a few 

 important examples of which may be noted in the Dog, Fox, 

 Wolf, Cat, Lion, Tiger, Bear, Raccoon, Mink, Skunk, and into 

 the aquatic types, such, for example, as the Seals, Sea-lion, and 

 Walrus. The aquatic forms exhibit considerable structural adap- 

 tation for their water life, including completely webbed digits. 



Order 6. Cetacea. This is a rather small order of exclusively 

 marine animals, and includes the Whale, Porpoise, and Dolphin. 

 They are tremendously modified for their mode of life, probably 

 more so than any other order of Mammals. The teeth are re- 

 stricted to one jaw or lacking entirely in the adult, as is also the 

 hairy covering. No hind limbs are present. The largest living 

 animal, the Sulfur-bottom Whale (Sibbaldus sulfurous), may 

 reach a length of nearly a hundred feet and a weight of close to 

 300,000 pounds. (W. fs. 90, 206.) 



Order 7. Sirenia. A small and relatively unimportant order 

 of aquatic Mammals, including the Manatee and Dugong. Only 

 seven species are known, three of which are found along the At- 

 lantic coast. The Florida Manatee (Manatus americanus) is the 

 best known. The order is characterized by the fin-like fore limbs, 

 the absence of hind limbs, and the peculiar horizontal tail fin. 

 (W. f. 91.) 



Order 8. Ungulata. Among the Ungulates, Man has for ages 

 found some of his most important animal allies, including such 

 almost indispensable species as Horses, Cattle, Sheep, Hogs, 

 and Camels. These species he has long since domesticated to 

 provide a constant supply of animal food, materials for clothing, 

 and transportation. We can characterize the Ungulata as the 

 hoofed mammals, and they may be divided into the even-toed 

 and odd-toed types. Thus the Cow, Pig, and Camel may be 

 given as examples of the even-toed Ungulates, while the Horse, 

 Rhinoceros, and Elephant are examples of the odd-toed. The 

 modification of the pentadactyl limb probably reaches a climax 

 in the monodactyl appendage of the Horse. Other noteworthy 

 structural features of certain Ungulates include the peculiar stom- 

 ach of the Ruminants which permits a regurgitation of food for 

 further mastication ; the very large antlers of the Moose and Deer, 

 which are shed annually ; the horns which develop on certain 

 head bones of the Rhinoceros ; and the tremendous trunk, or 



