350 ELEMENTARY ZOOLOGY. 



The three most important orders are the hoofed mammals (as the 

 cow, horse, etc.), the clawed or flesh-eating animals (as the cats, 

 dogs, etc.), and the primates (to which the monkeys and men 

 belong). Beside these there are four other North American orders 

 of less importance: the rodents (rats and mice, etc.), the insectivorous 

 mammals (moles), the bats, and the whales. The sloths and 

 armadillos are lowly types found in the southern part of North 

 America and in South America. They are known as edentates, or 

 toothless mammals. 



FIG. 148. Duck-bill (Orniihorhynchus anatinus). Photo by Folsom. 



Questions on the Figure. What are the peculiarities of the 

 species? What does the structure of its feet suggest as to its habits? 



346. Whales, Porpoises, and Dolphins (Cetacea). 



Because of their life in the water and their adaptations 

 to it these animals are often looked upon as fishes. While 

 whales include our largest animals, reaching 80 or even 

 100 feet in length, some of the species are not more than 

 four to eight feet in length. They have little hair and 

 their teeth may disappear or be replaced by " whale-bone, ' ' 

 which serves as a strainer to retain the small fish, and 

 Crustacea, etc, when the water is forced out of the mouth 

 after a "catch." The function which hair serves in 



