CLASS MAMMALIA. 179 



CLASS MAMMALIA (mam ma'li a). 



General Characteristics. To the class of MAMMALS be- 

 long man and those animals which resemble him in the 

 most important parts of their organization. The distin- 

 guishing features of this class are, that they suckle their 

 young, and that their bodies have, in general, a full or 

 partial covering of hair. Some being designed for a life 

 purely terrestrial, others mainly aerial, and others aquatic, 

 they exhibit, as compared with the birds, great variety 

 of structure, as will appear in the following tabulation 

 for Orders : * 



ORDERS. EXAMPLES. 



OVIPAROUS FORMS, BIRD-LIKE Mon 5 trem' a td. ..Duckbill. 



YODNG CARRIED IN POUCH Mar su pi (l'H a Opossum, etc. 



TOOTHLESS FORMS Eden td'td Sloth., etc. 



FORMS WITH GNAWING TEETH Hoden'tld Eat, etc. 



SMALL BURROWING FORMS In sec fiv'o rd Mole, etc. 



FLYING FORMS Chei rbp'te rd Bat. 



WHALE-LIKE, CARNIVOROUS Ce ta'ce d Wliale, etc. 



WHALE-LIKE, HERBIVOROUS SI re'nl d Manatee, etc. 



FORMS WITH PROBOSCIS Pro bos cld'e d. . . .Elephant. 



FEET PARTLY HOOFED, GNAWING FORMS Hyracotd'id. Coney. 



FOUR FEET HOOFED, GRAZING FORMS Un ffu lit' td Horse, etc. 



TEETH COMPLETE, FLESH EATERS. . Car nlv'o rd Cat, etc. 



FORMS WITH PREHENSILE FEET, NON-ERECT Quadrumd'nd Monkey. 



ERECT, TWO-HANDED El ma' nit Man. 



valuable for destroying the larvae of almost every insect found upon or (within 

 the length of its bill) beneath the surface of the soil. Wherever the Robins and 

 birds of similar habits are destroyed, these insects and worms increase to an 

 alarming extent. A wise Creator has designed the birds not only for ornament 

 and pleasure, but to serve a definite purpose in protecting vegetation. Prudence 

 would teach us to protect them as our faithful servants. 



* Dental Formula. As the teeth present important characteristics for classi- 

 fying the Mammals, zoologists designate the number by a formula, which, as 

 applied to man, reads thus : 



.2 2 11 2 2 33 



* 2=2" P 1 = 1' ^ 2 = 2' m 3=3 = 32< 



This signifies that there are eight incisors, two on each side of each jaw ; four 

 canine teeth back of the incisors ; eight premolars (bicuspids) back of the canine ; 

 and twelve molars back of the premolars. 



