232 



THE MAMMALIA. 



are met with in a row at the same time (for 

 instance, in the widely distributed Mastodon angus- 

 tidens) ; and as, moreover, they follow upon one 

 another as milk teeth and permanent teeth ; and, 

 further, as several typical mastodons of this kind 



FIG. 40. The used Molar of Mastodon angustidens. 

 a a', b b 1 , cc', Transverse ridges ; one-half nat. size. 



have, besides the upper tusks, lower ones as well, 

 and between them other two smaller incisors, 

 this species of dentition moves wholly within 

 the limits and forms known to us. The mastodons 

 referred to are those of the Middle and Upper 



