LESSONS IN ZOOLOGY. 311 



pointed horns, while the horns of the elk and reindeer are broad 

 and flat at the extremities. The horns are borne only by the 

 males, except in the case of the reindeer. The cervidse have eight 

 incisors in the lower jaw working against a callous pad in the 

 upper jaw; occasionally canines occur in the upper jaw. There 

 are twelve grinders in each jaw, which are separated on the lower 

 by a little space from the incisors. The young of nearly all spe- 

 cies are spotted. The spines of the dorsal vertebrae are long, bet- 

 ter fitting them for the origin of the strong ligaments which 

 support the head with its load of horns. 



The Cavicornia have hollow horns in both sexes, no canines, 

 but twelve grinders in each jaw with six incisors in the lower. 

 In this group belong the antelope, gnu, gazelle and chamois; 

 the sheep, goat, ibex, Rocky Mountain goat and others ; the 

 musk ox, the American bison, and the Indian buffalo and the do- 

 mestic ox the sheep and the ox, the horse and hog being the 

 most important and valuable domestic animals ol the temper- 

 ate and warm temperate zones. 



The Proboscidea include the elephants and several extinct 

 animals, all of great size. They are characterized by a long flexi- 

 ble proboscis, which is an organ of touch and of prehension as 

 well. The skin is very thick and sparsely covered with hair, 

 though some of the extinct forms had an abundant coat of hair. 

 They have several toes on each foot furnished with hoofs, but 

 walk on thick pads of integument. The tusks are two upper in- 

 cisors; some extinct forms had lower tusks as well. The grind- 

 ers are seven on each side in each jaw, but they grow forward 

 gradually so that never more than one or parts of two are in 

 service at one time, the earlier ones dropping out and new ones 

 coming in. The grinders of the elephant are considerably longer 

 than wide, and are made up of thin alternate layers of enamel, 

 dentine and cement, showing a flat surface, while the teeth of the 

 mastodon show a tuberculatecl surface. The mammoth and mas- 

 todon seem to have been vegetarians, living in damp shady places, 

 much like the elephants of Africa and Asia of to-day. One extinct 

 form had tusks curving downward from the lower jaw. 



