4 6 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



dently is not extended posteriorly so much as in Phenacodus. The 

 transverse processes are slender and curve sharply backward and are 

 pierced anteroposteriorly, close to the centrum, by a large ver- 

 tebrarterial canal on each side. The anterior aperture of the canal 

 is immediately posterior to, and somewhat recessed behind, the out- 

 ward flaring lateral margin of the atlantal facet or surface. The 

 odontoid process is stout and nearly cylindrical. 



The succeeding cervical vertebrae decrease in length posteriorly 

 with the centra somewhat flattened dorsoventrally and with surpris- 

 ingly large and relatively broad neural canals. The breadth of the 

 neural arch dorsally is evident in the transversely wide spacing of the 

 zygapophyses. The transverse processes extend prominently outward 



Fig. 5. — Meniscotherium chamense Cope. Cervical and anterior dorsal ver- 

 tebrae (U.S.N.M. 22672) ; a, lateral view; b, ventral view. yl-X natural size. 

 New Fork member, Wasatch formation, Green River Basin, Wyo. 



and downward from essentially the anterior half or two-thirds of the 

 centrum, the sixth cervical showing the characteristic posterior exten- 

 sion or expansion of the inferior lamella. The vertebrarterial canal, 

 as in the atlas and axis, is a conspicuously large foramen in all except 

 the seventh which, lacking the inferior lamella, may show a broad 

 groove on the lower surface of the transverse process close to the 

 centrum. The spinous processes are low on the third to about the 

 sixth cervical, but the seventh shows some elongation and a slight 

 backward tilt. The inferior surfaces of the centra are comparatively 

 broad and flat without hypapophyses (see figs. 5 and 6), although 

 the axis to the fifth cervical shows a low keel which posteriorly on 

 each broadens into a triangular flat hypapophysial table, as noted by 

 Cope (1884b) for both Meniscotherium and Phenacodus. Also, as 



