EXPLANATION OF PLATE VI. 



Figs. 1-4. Agathaumas sylveatre, one-fourth natural size. 



Fig. 1. A? rib. 



Figs. 2-3. Undetermined bones. 



Fig. 4. Neural arch of a dorsal vertebra minus the processes. 



Figs. 5-8. Bottosaurus perrugosns, one-half natural size. 



Fig. 5. A posterior dorsal vertebra from front : a, from behind, and, h, from below. 



6. Posterior part of mandibular ramus from outer side ; J, from inuer side. 



7. Portion of dentary bono with alveoli: a, from inner side ; 6, from outer side. 



8. Distal end of femur fouud with the preceding ; a, lateral view. 



Figs. 9-16. Fragments of tortoises from the Cretaceous of Colorado, natural size. 

 Fig. 9. Plastnmemts punctttlatus, costal bone. 



10. P. insiynis, byposternal bone. 

 Figs. 11-12. Adnata lincnlatus : 11, from plastron ; 12, vertebral bone. 

 13-14. Trionyx vagans, portions of costal bones. 

 15-10. Marginal bones of Cumpsemys vicim. 



