MESODONTA. 219 



anterior tubercles, of which the inner is represented by two distinct cusps 

 in one or more of them, and the external is crescentoid in section. The 

 posterior part of the crown is wide and concave, and is bordered at its pos- 

 terior angles bv an obsolete tubercle on the inner and an elevated anffle on 

 the outer side. In the T. rostratmn, the type of the genus, the middle incisors 

 have transverse cutting-edges. 



This genus is allied to Adapis Cuvier, of the French Eocene, bvit differs 

 in the possession of but two incisors on each side; in Adapis, there are 

 three, according to Filhol. From that genus and Opisthotomus, it differs 

 also in the structure of the last inferior molar, as exhibited in the analytical 

 table. 



An account of the osteology of this genus, so far as indicated by my 

 material, was given in the papers above refen-ed to. It was shown that the 

 hind limbs, especially the femur, are quite elongate, more so than the fore 

 limbs, and that the proportions of both fore and hind limbs are slender. 

 The head of the radius is subround, and its distal extremity a subequilateral 

 triangle. The humerus is distally expanded, with large inner and outer 

 epicondyles and an arterial foramen. The tuberosities of its head are small. 

 The ilium is rather narrow and flat, except at the acetabulum, where it 

 supports a large anterior inferior spine. 



The first impression derived from the appearance of the lower jaw and 

 dentition, and from the humerus, is that of an ally of the coati {Nasua). 

 The humerus, indeed, is almost a fac-simile of that of Nasua, the only 

 difference being a slight outward direction of the axis of the head. The 

 same bone resembles also that of many marsupials, but the flat ilium, 

 elevated position of dental foramen, and absence of much inflection of the 

 angle of the lower jaw, etc., render affinity with that group highly improb- 

 able. The length of the femur indicates that the knee was entirely free 

 from the body as in the Quadrumana, constituting a marked distinction from 

 anything known in the Carnivora, including Nasua. The round head of 

 the radius indicates a complete power of supination of the fore foot, and is 

 different in form from that of Carnivora, including Nasua ; and, finally, the 

 distal end of the radius is still more different from that of Nasua, and 

 resembles closely that of Semnopithecus. 



