288 



Annals of the Carnegie Museum. 



Lama huanaco, here used for comparison, the corresponding foramen 

 is slightly further back (opposite the anterior portion of m 1 ). 



The general outline of the lower jaw is quite similar to that in the 

 recent genus. The diastemata in front of the molar series are, how- 

 ever, shorter, as are also the coronoid processes. The inferior sigmoid 

 notch is shallower, and the posterior face of m 3 is closer to the base 

 of the coronoid process than in Lama huanaco. 



Cervical Vertebra. — The atlas and axis are not present in the type 

 but the succeeding cervicals are all represented. The third cervical 

 vertebra is represented only by the posterior portion, which is identi- 

 cal, except in the smaller size, with that in Oxydactylus lo?igipes Peter- 

 son. The fourth cervical is very nearly complete and is very long 

 and slender. The neural spine is represented only by a small rugose 



Fig. 2. Fourth cervical vertebra 

 of Stenomylus gracilis. Left side. 

 Type No. 1610. \ nat. size. 



Fig. 3. Fifth cervical vertebra 

 of Stenomylus gracilis. Left side. 

 Type No. 1610. \ nat. size. 



elevation on the superior face in the middle of the neural arch. The 

 neural canal is of fairly large size and subcircular in outline. The 

 prezygapophyses are well separated by a deep emargination of the 

 neural arch, while the postzygapophyses are separated only by a very 

 shallow emargination as in Oxydactylus longipes and unlike that in 

 Lama huanaco. On the ventral surface is a very strong keel which 

 results in giving to the posterior face of the centrum a subtriangular 

 outline. The anterior face of the centrum is quite hemispherical. 

 The anterior division of the transverse process projects outward and 

 downward and the posterior portion projects more directly outward. 

 There is no visible vertebrarterial canal. On the whole the vertebra 

 is, except for its smaller size and less developed neural spine, almost 

 identical with that of Oxydactylus longipes. 



The fifth cervical differs from the fourth practically only by its 

 greater robustness. Its neural spine is very little increased in size and 

 the bone as a whole is slightly shorter than the preceding vertebra. 



