154 



length or anteroposterior diameter of the molar, are thicker in propor- 

 tion to the intervening spaces, and the quantity of cement is therefore 

 smaller, the enamel is also more strongly plicated. 



From the tertiary formations of Ohio, North America. 



Purchased. 



621. A portion of the upper jaw of a Mammoth, with the molar of the right 

 side in situ, and part of the sockets of the tusks : the antero-posterior 

 extent of the grinding surface of the molar is nine inches, and the com- 

 mon dentinal base of the transverse plates is exposed by attrition to an 

 extent of nearly two inches at the anterior part of the grinder ; in an ex- 

 tent of seven inches of the succeeding part of the grinding surface, the 

 summits of thirteen plates are exposed. If this specimen be compared 

 with the Mastodon elephantoides, the palate will be seen to be much 

 more deeply excavated, and the diastema between the molar and tusk of 

 much greater depth in the Mammoth. 



From the tertiary deposits of the Ohio, North America. 



Purchased. 



622. The symphysis and part of the right ramus of the lower jaw of a Mam- 

 moth, with one of the molars in situ. The summits of all the transverse 

 ridges are exposed by attrition, and of these the crown, in a length of 

 five inches, exhibits thirteen. The margin of the jaw anterior to this 

 tooth descends, as in the Elephant, obliquely downwards to a pointed and 

 narrow symphysis ; the anterior outlet of the dental canal is two inches 

 below the beginning of this declivity. This tooth, as compared with the 

 corresponding one in the Asiatic Elephant, is broader in proportion to 

 its antero-posterior extent, especially at the two extremities ; in the 

 Elephant's tooth compared with it, the abraded surface of the crown, 

 which is five inches in extent, shows the summits of eleven transverse 

 plates, and manifests the same differences in the less breadth of the tooth, 

 the narrower interspaces of the plates, and the more plicated disposition 

 of the enamel, which have been noticed in the description of the upper 

 molar, No. 567- 



From the tertiary formations of the Ohio, North America. 



Purchased. 



