161 



Genus Mastodon. 



Mastodon elephant oides. 



663. A mutilated and petrified cranium of the Mastodon elephantoides, Clift. 

 The posterior fractured surface displays the large cancelli which are there 

 developed, as in the Elephant. 



From the tertiary formations of the Sub-Himalayan district, India. 



Presented by JFalter Ewer, Esq., F.R.S. 



664. A portion of the upper jaw of the Mastodon elephantoides, Clift. It 



includes four molars and the intervening bony palate : the grinding sur- 

 face of the anterior molar on each side measures seven inches and a half, 

 and exhibits seven transverse ridges and a posterior talon ; this has not 

 yet been abraded ; the mammillary summits of the last ridge have just 

 begun to be worn ; the dentine is exposed in all the anterior ridges, and 

 to a greater depth as thev advance forwards, the common base of the two 

 anterior ridges being there exposed. The posterior grinder, three of the 

 ridges of which have emerged from the socket, is situated almost at right 

 angles with the antecedent tooth, the summits of the ridges being directed 

 backwards ; it must describe the same degree of revolution in attaining 

 the position requisite for the office of mastication, as the molars do in 

 the Elephant : the anterior interspace of the right and left molars is one 

 inch and a half across, the bony palate gradually widens, as it extends 

 backwards, to about four inches ; its posterior margin is excavated by a 

 rectangular notch rounded off at the apex. The palate presents a deep 

 transverse excavation, two inches in antero-posterior extent, between the 

 grinder and the socket of the tusk ; a portion of this socket, with a frag- 

 ment of the base of the tusk, is preserved on the left side. This part of 

 the tusk descends almost vertically at right angles with the plane of the 

 anterior molar, and with a very slight bend, which is convex towards that 

 molar. On the right side of this instructive fragment the anterior smaller 



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