302 F. JB. Loomis — Osteology and Affinities 



as it does rather a wide convex rectangular area which must 

 have allowed very free movement to the lower jaw, both later- 

 ally and vertically. The postglenoid facet is practically verti- 

 cal and closely appressed to the bulla, the two facets (glenoid 

 and postglenoid) being separated by a gap, as is the case in 

 modern camels. The tympanic bone is fused to the squamo- 

 sum, the external auditory meatus being a closed slightly pro- 



Fig. 3. 



Fig. 3. Stenomylus hitchcocki, side view of the skull, x 1/ 2. 



jecting ring ; while the greatly inflated bulla is filled with 

 cancellous bone, as is the case in Tylopoda generally. The 

 bulla is also fused to the paroccipital process for most of its 

 length. The occipital bones are all fused, and the occiput is 

 narrow and small. The two condyles are sessile, and do not 

 project behind the plane of the occiput. Below, their facets 

 do not quite meet, being separated by a narrow^ groove of about 

 a millimeter, the groove being, however, much wider in 

 youthful specimens. The pterygoids unite with the pala- 

 tines to make deep plates projecting below the base of the 

 skull. The posterior nares open between the palatines so far 

 forward as to make a very short hard palate. The front of 

 the naral opening is opposite the front of the second molar, 

 which in general is very far forward for this opening. How- 

 ever, in the Tylopoda generally it is characteristic to have the 

 posterior nares open well forward : so that this genus simply 

 shows a somewhat higher specialization in this feature. I feel 

 that the compression of the muzzle by the preorbital and sub- 

 nasal pits tends to cause the posterior opening of the respira- 

 tory passage to emerge into the mouth as far forward as 

 possible. 



The mandible is decidedly deep for so slender a creature, 

 but the reason for this is readily seen in the extreme hypso- 

 dont condition of the teeth, which in a recently mature indi- 

 vidual extend nearly to the bottom of the jaw. The symphysis 



