PLATE XV. 



PAGE 



Fig. 1. Tooth of Ccelueus gracilis Marsh. Natural size. Near Muir- 



kirk. (3336 G. C.) (After Marsh.) 187 



Figs. 2-5. Pleuroccelus nanus Marsh. (After Marsh.) 188 



2. Posterior cervical vertebra, x ^/^- Near Muirkirk. (5678 U. S. 



N. M.) 

 2a. Section of same at line a-b. 

 3a. Supra-occipital, superior view. X V2- Near Muirkirk. (5692 



U. S. N. M.) 

 3b. Same, posterior view. 

 3c. Same, inferior view. 



4. Dorsal vertebra, x %• Near Muirkirk. (4968 U. S. N. M.) 



f. Lateral cavity (pleurocoele). 



a. Anterior end. 



p. Posterior end. 



n. Neural canal. 



s. Suture for neural arch. 



5. Sacral vertebra. Left lateral and posterior views. X V2- Near 



Muirkirk. (4946 U. S. N. M.) r. Facet for rib, other lettering 

 as in Fig. 4. 



5U 



