147 



deni. The vertebral scute impressions likewise most nearly resemble those 

 of the latter but are proportionately broader, and the posterior border of the 

 third vertebral scute crosses, as usual, the fifth vertebral plate. 



The interior of the carapaceal specimen being freed from matrix, exhibits 

 the costal plates with strong, well-developed costal capitula. 



The plastron is flat ; rather more strongly notched at its posterior extremity 

 than in the former specimens in which it is preserved. 



The thickness of the costal plates ranges from 2 to 4£ lines. The thick- 

 ness of the hyposternal plates internally ranges from 5-£ to 8 \ lines. 



8. An eighth specimen, consisting of the greater part of a plastron with 

 fragments of the carapace, was obtained by Dr. Carter near Lodge-Pole Trail, 

 thirteen miles southeast of Fort Bridger, and presented to the Academy of 

 Natural Sciences. 



0. A fragment of a carapace, from Grizzly Buttes, presented to the Acad- 

 emy of Natural Sciences by Dr. Joseph K. Corson, United States Army, 

 has the intermediate scute impressions much longer than the width, not more 

 so, however, proportionately, than in the nearly complete specimen numbered 

 as the sixth. 



10. A similar fragment of an apparently young specimen, presented by 

 Dr. Carter, has the second vertebral scute impression nearly equal in length 

 and breadth ; and the third one .is but little longer than the breadth. Their 

 lateral grooved borders are strongly double-sigmoid. 



11. Part of a carapace and plastron of a still younger specimen, obtained 

 by Dr. Carter near Lodge-Pole Trail, twelve miles southeast of Fort Bridger, 

 nearly agrees in the form and proportions of its corresponding vertebral scute 

 impressions with that last described. The second is nearly of equal lengfh 

 and breadth; the third and fourth are wider than the length. In its details 

 of structure it accords sufficiently with the older and more complete specimens 

 to render it probable that it pertained to the same species, except that the 

 carapace is obtusely carinated its entire length. The cntpsternal bone is more 

 rounded at its fore part than in previous specimens, and its length is about 

 equal to the breadth. 



12. A fragment of a plastron of another young individual, from the same 

 locality and gentleman as the preceding, nearly agrees with the corresponding 

 part. The entosternal is a little longer than broad, and is pyriform, with lat- 

 eral projecting angles.. 



