54+ 



FOSSIL TURTLES OF NORTH AMERICA. 



are 3 mm. or less in diameter. On the outer ends of these costals the pits are even smaller, 

 and are arranged more or less in rows across the costals. On the nuchal the pits are small and 

 shallow. 



To this species is referred the specimen represented by fig. 702. It was collected by the 

 American Museum expedition into the Bridger deposits in 1903. The more exact locality 

 is the eastern part of Grizzly Buttes, Wyoming. The number of the specimen is 5910. 



Only small portions of the carapace are missing. The median region of the nuchal is 

 gone, and the second and third neurals. There are 8 pairs of costal plates, but the eighth pair 

 is vestigial and might therefore be missing in other individuals ol the same species. The 

 total length of the carapace is 286 mm., the width almost exactly the same. Originally the upper 

 surface may have been about as convex as the carapace of Platypcltis ferox, of Florida. 



There is no preneural. The length of the first neural is 50 mm.; its width anteriorly, 

 31 mm., posteriorly, 16 mm. The fourth neural is 29 mm. long, 18 mm. wide. The fifth is 

 25 mm. long, 14 mm. wide. The sixth neural is pointed behind, 17 mm. long and of about the 

 same width. It permitted the costals of the sixth pair to meet in the midline behind it. It is 

 uncertain whether or not there was a small seventh neural. 





701. 



Figs. 701 and 702. Platypeltis heteroglypta. Carapaces. X|. 

 701. Carapace of type. 702. Carapace of No. 5910 A. M. N. H. 



The nuchal of this specimen is of greater extent fore and aft than in the type, being about 

 33 mm. The distal ends past beneath the border of the first costal plate, but apparently not 

 beneath the rib of that costal. The free ends of the carapacial ribs projected beyond the mar- 

 gin of the shell about 27 mm. 



The sculpture resembles closely that of the type specimen, consisting of large cells on the 

 neurals and the proximal ends of the costals and of smaller cells on the distal ends of the 

 costals. On the distal ends of the costals the cells are arranged somewhat in rows parallel 

 with the adjacent border of the carapace. 



Any possible doubts regarding the specific position of the specimen would arise from the 

 fact that the nuchal is somewhat broader from front to back than in the type; that the costals 

 are somewhat thinner, being only about 5 mm.; and that the free ends of the costals are 

 beveled down to an acute edge, instead of being more or less obtuse as in the type. The dis- 

 tance from the hinder border of the carapace to the suture between the second and third 

 costals is almost the same in the two specimens under consideration; but the width of the 

 carapace of the recently acquired specimen is about 30 mm. greater than in Cope's type. 



It is not believed that these differences indicate a distinct species. The thinness of the 

 bones may be due to pressure during the early stages of fossilization; the greater width of the 

 carapace to a more advanct age. 



