199 



completely petrified and impregnated with iron, and was associated with 



rium. 

 Presented by Dr. Harlan. 



remains of Mastodon, Mammoth and Megatherium 



Subgenus Coryphodon*. 



826. The cast of the fragment of the right ramus of the lower jaw of a tapiroid 

 Pachyderm nearly allied to the genus Lophiodon, Cuv., with the last 

 molar and part of the penultimate molar in situ. These teeth indicate 

 an animal as large as the Lophiodon Isselanus (Grand Lophiodon dTssel), 

 Cuv., and as the Lophiodon medius, Cuv. ; but the jaw, though less deep 

 than in the Lophiodon bathygnathus, is deeper in proportion than in the 

 Lophiodon Isselanus, and, a fortiori, than in the Lopk. medius, which is 

 surpassed in this respect by the Lophiodon Isselanus. But the more im- 

 portant differences, which determine at least the subgeneric distinction of 

 the extinct Pachyderm indicated by the present fossil, are manifested by 

 the last molar tooth, which is fortunately entire. It has a smaller 

 antero-posterior diameter of the crown in proportion to its transverse 

 diameter, which chiefly depends on the much smaller size of the third or 

 posterior ridge or talon. From the outer extremity of each of the two 

 transverse eminences a ridge is continued obliquely forwards, inwards and 

 downwards : the anterior one extends to the inner and anterior angle of 

 the base of the crown, the posterior terminates at the middle of the inter- 

 space between the two ridges. The anterior principal transverse eminence, 

 although it has a trenchant summit, as in the known Lophiodons, yet the 

 edge is more concave, the outer and inner extremities rising each into a 

 conical point. The posterior transverse eminence is much lower than the 

 anterior one and is trituberculate ; the trenchant margin, connecting the 

 outer and inner points, does not extend across the crown parallel with the 

 anterior ridge, as in the Lophiodon, but forms an angle posteriorly where 

 it developes a third point, which is the highest : from this point the pos- 

 terior ridge or talon extends downwards and outwards upon the back part 

 of the crown. Thus the crown of the last molar in the present genus has 



* Kopv<pfi a point, liSovs a tooth. 



