EXPLANATION OF PLATE XXXV. 



All tho figures oue-lialf the uatural size except Fig. 14, which is of the natural size. 



Figs. 1-11. Tylosaurus dyspblor. • Specimens from the Cretaceous of New Mexico, and helonging to 

 the Smithsonian Institution. 



Fig. 1. Ai'ticular ball of a posterior dorsal centrum. 



Fig. 2, 3. Tho same of two other specimens, exhibiting a successive increase of compression 



from above downward. 

 Fig. 4. Articular ball of a caudal centrum. 

 Fig. 5. Left lateral view of the same. 



Fig. 6. Articular ball of a more posterior caudal centrum. * 



Fig. 7. Left lateral view of the same specimen, exhibiting the reduction iu the size of the 



diapophysls. > 



Fig. 8. Left lateral view of a more posterior caudal vertebra, devoid of diapophyses. 

 Fig. 9. Supijosed femur, posterior view. 

 Fig. 10. Supposed fibula. 

 Fig. 11. Supposed tibia. 



Figs. 12, 13. Tylosaukus proriger. Specimens from the Cretaceous of Kansas, belonging to the 

 Smithsonian Institution. 

 Fig. 12. Extremity of the snout, or of the premaxillary. 



.Fig. 13. Posterior articular surface of the left spleuial bone of the lower jaw. 

 Fig. 14. Tooth of a mosasauroid, uatural size, from tho Cretaceous of L'Eau qui Court 

 County, Nebraska. The crown is compressed, conical, with acute borders and smooth sur- 

 faces. The base is compressed oval, and it exhibits on its inner side a small concavity for 

 the accommodation of a successor. 



