MAMMALS 



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Rodents. — The mammals are divided into a number of smaller 

 groups, called orders. The rabbit, because it has prominent 

 incisor teeth and no canine (dog) teeth, is placed in the order 

 of the rodents. Among the fourteen orders of mammals the 

 rodents are estimated to comprise fully one half of the total 

 number of species. 



Although most rodents may be considered as pests (as the rat 

 and mouse), others are of use to man. Some of this order furnish 

 food to man, as the rabbit, hares, and squirrels. The fur of the 

 beaver, one of the largest of this order, is of considerable value, 

 as are the coats of several other rodents. The fur of the rabbit 

 is used in the manufacture of felt hats. The quills of the por- 

 cupines (greatly developed and stiffened hairs) have a slight 

 commercial value. 



Other Orders of Mammals. — The lowest are the monotremes, ani- 

 mals which lay eggs hke the birds, although they are provided with hairy 

 covering like other mammals. 

 Such are the spiny ant-eater and 

 the duck mole. 



All other mammals bring 

 forth their young alive. The 

 kangaroos and opossum, how- 

 ever, are provided with a pouch 

 on the ventral side of the body in 

 which the very immature, blind, 

 and helpless young are nourished 

 until they are able to care for 

 themselves. These pouched ani- 

 mals are called marsupials. 



The other mammals, in which the young are born able to care for them- 

 selves, and have the form of the adult, may be briefly classified as follows : 



Virginia opossum. From photograph, one eighth 

 natural size, by N. F. Davis. 



Character 

 Edentates Toothless or with very simple 



teeth 



Rodents Incisor teeth, chisel-shaped, usu- 



ally two above and two be- 

 low 



Cetaceans Adapted to marine life, teeth 



sometimes platelike 



Examples 

 Ant-eater 

 Sloth 

 Armadillo 

 Beaver, Rat 

 Porcupine, Rabbit 

 Squirrels 

 Whales 

 Porpoise 



