﻿278 Allen's naturalist's library. 



Mammals that can by any possibility be included in the Mar- 

 supials, are two minute ones from the reputed Triassic rocks 

 of North Carolina, one of which has received the name of 

 Drj;iiatheriu7ft sylvestre. The total number of teeth in the 

 lower jaw is fourteen on each side, three of which are incisors, 

 one a canine, three premolars, and the remaining seven molars. 

 The latter differ from those of all Mammals in which the 

 teeth are differentiated into series, in having imperfectly 

 divided roots, thus approximating to those of reptiles. The 

 premolars are nearly simple cones ; while the molars, as shown 

 in Fig. 2 of the diagram on page 274, consist of one main 

 cone, with minute accessory cusps on the edges ; and it is 

 probable that the opposing teeth of the upper and lower jaws 

 mutually interlocked, thus displaying another reptilian fea- 

 ture. 



Whether this exceedingly primitive creature was really a 

 Marsupial may be open to doubt, even if it be a Mammal at 

 all. Assuming, however, that, as is probable, it is really 

 Mammalian, it may equally well indicate an Order more nearly 

 allied to the Monotremes than to the Marsupials, being, in 

 fact, an ancestral type of the former. Our information is, 

 however, at present far too meagre to admit of anything de- 

 finite being said on this point. 



