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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 77 



not meet its fellow of the opposite side, thus leaving the spinal cord 

 exposed for a considerable space, a condition also found in Scelido- 

 saurus as well as in the ceratopsian dinosaurs. 



The axis centrum is heavier than that of the atlas but apparently 

 subequal in lengtli. The posterior articular face is deeply cupped, 



FiGORE 6. — Atlas and axis of Palaeoscincus rugosidens. Type. 

 No. 11868, U.S.N.M. A, Lateral view ; B, Posterior view of 



AXIS, ABOUT ONB-THIED NATURAL SIZE. At., ATLAS : .la;., AXIS ; 1st C. 



R.J First cervical rib 



as shown in Figure 6B. The lateral surfaces are concave and there 

 is a heavy median keel, on either side of which, on the anterior half, 

 are well developed parapophysial facets. The neural arch is low 

 and massive. The postzj^gapophyses strongly overhang the poste- 

 rior border of the centrum. Their articular faces are flat and es- 



