EXPLANATION OF PLATE XXI. 



Fig. 1. Posterior dorsal vertebra of Platecarpus coryplimis: a, from front; h, from behind. 



2. Dorsal vertebra near the position of the last, from below. 



3. Platecarpus <ec(«r«s, specimen from Butte Creek; middle cervical vertebra: a, vertebra, from 



above ; T>, from below. 



4. Anterior cervical vertebra ; 4 h, from below. 



5. Cervical vertebra, more anterior; 6, centrum, from below, 

 fi. Anterior dorsal vertebra, from front; o, from above. 



7. Platecarpus ciirtirostris, one-half uatnral size; a, axis, from behind ; 6, from below. 



8. Platecarpus curtirostris, third cervical: a, from front; b, from below: o, from behind: (f, from 



above. 

 Figs. 9-11. Anterior dorsal vertebra* of the same species: a, views from front; V, from behind; c, from 



above. 

 Fig. 12. Median dorsal, from the front. 



13. Posterior dorsal: a, from front; h, from behind ; c, from below. 



14. Clidastcs ciiieriarum, Cope, postero-median dorsal vertebra: a, from front; 4, from behind; 



c, from below ; d, from the side. 



15. Lumbar vertebra : a, from the side; I), from behind; c, from below ; d, from above. 



16. Anterior ciudal vertebra : o, from front ; 6, from side. 



17. Palatine tooth, natural size. 



