EXPLANATION OF PLATE XVI. 



All tbe figures of tlio natural size, except Figs. 13-17. 



Figs. 1-6. Ano.steira ohnata : 



Fig. 1. Portions of tlio carapace. 



Fig. 2. Portion of the same specimen, with portions of tlie plastron. Siiecimens collected 



by Dr. Carter in the vicinity of Fort Bridger. 

 Fig. 3. Inner view of tbrfee oostals, from a portion of the same specimen as Fig. 1, exhibiting 



the costal capitula. 

 Fig. 4. A third marginal plate from a larger individual. Dr. Carter. 

 Fig. 5. A fourth marginal plate of the left-side of another individual. From Washakia ; 



collected by James Stevenson. 

 Fig. 6. Section of a i^ygal plate. From a specimen found bj' Professor Haydeu at Church 



Buttes. 

 Fig. 7. Ilium of a turtle. Obtained at Grizzly Buttes by Dr. Carter. 



Figs. 8, 9. BjuSna arenosa : 



Fig. 8. Ilium of the right side, outer view. Fig. 9. Sacrum, inferior view. Sjiecimens ob- 

 tained from portions of the matrix, pertaining to the specimen of the shell represented in 

 Figs. 1, 2, Plate XIII. 



Fig. 10. Opisthocoelian caudal vertebra of a turtle. From near Lodge-ijolo trail. Dr. 

 Carter. 



Fig. 11. Fragment of a costal plate of a trionyx. From near Fort Bridger. Dr. Carter. 



Fig. 12. Fragment of a costal j)lat6 of a trionyx. From Little .Sandy Creek. Professor 

 Hayden. 



Figs. 13-17. Glyptosaxjrus. All magnified two diameters. 



Figs. 13-15. Osseous dermal plates of the body. Figs. 16, 17. Plates of the head. From 

 Grizzly Buttes. Dr. Carter. 



Figs. 18, 10. Oligosimus grand.evus : 



Fig. 18. Posterior view of a caudal vertebra. Fig. 19. Lateral view. Specimen obtained 

 by Professor Hayden's party on Henry's Fork of Green Kiver. 



