Douglass: Procamelus from Upper Miocene of Montana. 161 



portion is prismatic in form. The opening of the external auditory 

 meatus is a short sessile tube located at the upper extremity of the 

 tympanic, fusing behind with the mastoid process. The paroccipital 

 processes are flattened below and are oblicjue being directed antero- 

 internally and postero-externally. The outer portion terminates in a 

 small triangular process. The paroccipital processes extend forward 

 so that their anterior portions are partly internal to the tympanies. 



Top Vieiv. — The anterior portions of the nasals are gone. The 

 anterior processes of the frontal form a wedge between the posterior 

 rounded lobes of the nasals. The forehead between the orbits is 

 broad and is slightly convex transversely with a small median anterior 

 concave area. The supraorbital foramina are about two centimeters 

 external to the median line of the skull. The anterior margin of the 

 temporal foramen is nearly perpendicular to the longer axis of the 

 skull, but internally trends backward in a rapidly developing curve 

 continuous with that of the supratemporal ridges, which unite to form 

 the sagittal crest at a point a little less than one third of the distance 

 from the supraorbital foramina to the occiput. The .supratemporal 

 ridges are low and obscure. • The sagittal crest is long, thin, low in 

 front and quite high behind. The lateral wings of the occiput are 

 quite broad. 



The Mandible. — The horizontal portion of the mandible is quite 

 heavy, especially in front, but not deep, though it gradually increases 

 in depth from P2 to the ascending ramus. The angle of the mandi- 

 ble is broadly rounded, ending behind in a hook-like process. The 

 ascending ramus is narrow antero-posteriorly with heavy rounded 

 anterior and posterior ridges, which bound the masseteric fossa before 

 and behind. This fossa has the form of an inverted oval. The coro- 

 noid process is high and inclines backward. 



The Neck. — The atlas is broader than long. Beginning with the 

 axis, and including its process, each succeeding cervical is shorter than 

 the preceding or equals it in length. In Oxydactyliis the third cer- 

 vical is the longest and the cervicals posterior to it decrease in length 

 to the last. In Alticamelus altiis (Marsh), according to Matthew,^ 

 the cervicals vary in length from the longest to the shortest in the 

 following order: C. 3, C. 4, C. 5, axis, C. 6, C. 7, atlas. 



The spine on the axis is low, thin and rounded anteriorly, but is 



'"Fossil Mammals from Colorado," Mem. Amer. Miis. A'at. Hist., Vol. I, Part 

 VII, p. 431. See measurements. 



