EXPLANATION OF PLATE XXI. 



Fig. 1. Posterior dorsal vertebra of Platecarpus coryphteus: a, from front; b, from behind. 



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



3. Platecarpus iectulus, specimen from Butte Creek ; middle cervical vertebra : a, vertebra, from 



above; Z>, from below. 



4. Anterior cervical vertebra; 4 6, from below. 



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

 G. Anterior dorsal vertebra, from front ; a, from above. • 



7. Platecarpus curtiroslris, one-half natural size; a, axis, from behind ; b, from below. 



8. Platecarpus curtiroslris, third cervical: a, from front; b, from below: c, from behind; d, from 



above. 

 Figs. 9-11. Anterior dorsal vertebras of the same species: a, views from front; b, from behind; e, from 



above. 

 Fig. 12. Median dorsal, from the front. 



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



14. Clidastes cineriarum, Cope, postero-median dorsal vertebra: a, from front; b, from behind; 



c, from below ; <?, from the side. 



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



16. Anterior caudal vertebra : a, from front ; b, from side. 



17. Palatine tooth, natural size. 



