iro.2.] COPE ON MIOCENE KODENTIA. 367 



gives rise to a cross-ridge to the outer margin. In the mandibular 

 series the crests and crescents have a reversed relation. No cementum. 



To the above characters given by Dr. Leidy, I have added the absence 

 of postfrontal processes, and the superior position of the infraorbital 

 foramen. I now add that the pterygoid fossa is large, and that its inner 

 and outer plates are well developed, and subequal. The palate is ex- 

 cavated posteriorly. The acuminate anterior part of the malar bone ex- 

 tends as far forwards as the front of the orbit. There is no tuberosity 

 oil the side of the superior diastema near the premolar teeth. In the 

 mandible the posterior extremity of the incisive alveolus is not distinct 

 from the ascending ramus. 



Nothing has been heretofore published respecting the characters of 

 the remaining portions of the skeleton. Those which I possess are 

 the distal extremities of humeri, and a tibia, astragali, and portions of the 

 pelvis. The condyles of the humerus are narrow antero-posteriorly. The 

 internal flange descends at once to the fundus, leaving a long external 

 cylindrical portion without intertrochlear ridge. Anteriorly this portion 

 is cut into for half its length by the ligamentous fossse. There is a large 

 internal epicondyle, which is constricted by a neck at the base, and 

 j)resents a compressed edge inwards and upwards. The arterial canal 

 opens above on the interior side of the humerus. There is no external 

 epicondyle. 



The section of the ilium at its base and at its middle is triangular. 

 There is an angle along the middle of its external face which supports 

 a moderately prominent tuberosity, a little above the acetabulum. On 

 the anterior margin a little higher uj) is a short, comi)ressed, rather 

 prominent process, which probably represents the anterior inferior spine. 

 From this point posteriorly the internal face of the ilium is deeply con- 

 cave, producing an attenuation of the inner wall of the acetabulum. The 

 ischium is rather narrow at the base. 



The distal portion of the tibia is much like that of Arctomys, Gym- 

 noptychus^ and other Sciuridce. The posterior median process is very 

 large and is shallowly grooved ; the usual deep tendinous groove sepa- 

 rates it from the internal malleolus. The trochlear grooves are deep 

 and well seijarated ; the fibular surface is short. The head of the as- 

 tragalus is horizontally oval, and is separated from the trochlear i)or- 

 tion by a neck of moderate length. It extends obliquely inwards, so 

 that the internal margin of the head is interior to the line of the inner 

 margin of the trochlea. The sides of the latter are vertical. It is con- 

 siderably wider than long ; the trochlear carinse are marginal, and the 

 external is considerably more elevated than the inner. The separating 

 groove is profound but open. The posterior inferior fossa is small and 

 foramen-like. 



Besides the very different form and position of the infraorbital fora- 

 men, this genus differs from Gymnoptyclius in the excavation of the pos- 

 terior edge of the palate. 



