THE TEETH OF MAMMALS 173 



Each enamel plate is developed from a separate 

 tooth-pulp. 



The majority of the members of this order of 

 gigantic mammals are now extinct, though some 

 of them have survived to recent geological times. 

 The Mammoth of Siberia and glacial Europe was 

 a great hairy elephant, with enormous tusks 

 sweeping upward and backward in a circle. His 

 remains have been found in the flesh frozen in the 

 ice of Northern Siberia, and his image has been 

 discovered carved on his own ivory and upon rein- 

 deer horns by his contemporary, primeval man, in 

 the glacial caves of Europe. 



The bones of Mastodons are found all over the 

 United States in recent formations, and are some- 

 times associated with the bones and implements 

 of prehistoric man. The Mastodon had the 

 formula, — 



. 11 3-3 3-3 OQ 



i. :- — p.m. m. -- — = 28. 



1-1 P 3-3 3-3 



It had four incisor tusks, — two above and two be- 

 low in the center of the jaws. The upper tusks 

 were large, thick and strong, and sometimes at- 

 tained the length of twenty feet, describing a 

 sweeping curve outward. The two lower tusks 

 were small, straight, and projected horizontally 

 forward. The molars of the Mastodon differ 

 from those of the Elephant, but are plainly the 

 type of the forerunners of the latter. The latter 



