Pkikrsox : OsTROi.onv of Ox^•|)A( tvlus. 439 



off to a thin point, which is received into the dee\) notch of the jugal. 

 The glenoid cavity is a l)road flat plate of bone with great antero-pos- 

 terior extension, as in the recent camel. In the latter the articulation 

 for the condyle of the mandible is continuous with the glenoid process 

 at its internal margin, while externally the surface is interrupted by a 

 broad shallow groove. This character is repeated in O. longipes, but 

 the glenoid process is very much less developed in the latter genus. 

 In the llama the glenoid cavity is much shorter antero-posteriorly and 

 is entirely separated from the glenoid process by the broad shallow 

 groove referred to above. The postorbital process of the jugal meets 

 the corresponding process of the frontal, completely enclosing the 

 orbit posteriorly. Anteriorly the jugal apj^ears to extend farther than 

 does that of the llama and the rugosity for the attachment of the mas- 

 seter muscle is more prominent than in the recent genera. 



The lachrymal sutures are discernible along the junction with the 

 maxillary and this bone extends proportionally as far down on the face 

 as in the llama. The large vacuity characteristic of the Tylopoda is 

 situated immediately above the lachrymal. 



The frontals resemble those of Pocbrotheriiim and are somewhat 

 shorter than they are in the llama. Their widest diameter is above 

 the orbits. Posteriorly, they are V-shaped and are received into a 

 corresponding deep notch of the parietals. The supra-orbital ridges 

 are well marked and terminate in the downward projecting supra-or- 

 bital processes. Anteriorly the frontals extend no farther down on 

 the face than they do in PorbrotJieriuin. The fronto-nasal sutures 

 present a W-sha])ed character, sharper than that which is found in the 

 llama. 



The nasals are long and narrow splints of bone overlapping the pre- 

 maxillaries. As is well shown in PI. IV, Fig. 2, the posterior process 

 of each nasal is lance-shaped with blunt processes laterally and joins 

 the maxillary close to the facial vacuity, from which point the suture 

 extends anteriorly in a gently curved line constantly decreasing the 

 width of the nasals which are only 15 mm. wide at the anterior end. 

 On the whole, the nasals are proportionally shorter in O. longipes than 

 they are in PocbrotJierium, but much longer than in the llama. 



The paroccipital processes are very close to the occipital condyles 

 and are long, broad, and placed oblifjuely to the long axis of the 

 skull. The auditory bullae are filled with cancellous tissue and are 

 relatively smaller than in Pochroiiierium. Their position is somewhat 



