TESTUDINATA. 119 



Trionyx radulus Cope. 



Systematic Catalogue of the Vertebrata of the Eocene of New Mexico; U. S. Geo. Geol. Expl. W. 

 of 100th Mer., G. M. Wheeler, 1875, p. 3.5. Report Paleontology, do. iv. ii, p. 45. 



Plate xxvi, figs. 11-16. 



This turtle is nearly allied to the T. cariosus. As in it, the proximal 

 portions of the costal bones and the vertebral bones are honeycombed, 

 while the distal parts of the former are parallel-ribbed. Five to nine of 

 these ribs can be counted from the free end. They are not closely placed, 

 being narrower than their intervals. The size of the species is the same as 

 that of T. cariosus, but the costal bones are more uniformly thinner. 



A specimen from the Bridger beds shows a rather wide, smooth band, 

 along the front of the carapace. 



Measurements. 



K. 



Thickness at front of carapace at middle 010 



Thickness of a costal bone at middle of border 006 



Three ridges at end of costal in 010 



I have but one specimen of this species, in many fragments, from the 



Bridger formation. 



Trionyx guttatus Leidy. 



Trimyx guttatus Leidy, Report U. S. Geol. Surv. Terrs. (4to), p. 176, pi. ix, fig. 1. Cope, Report Expl. Surv. 

 W. of 100th Mer., G. M. Wheeler, iv. pt. ii,p. 46. T. uinlaensis Leidy, Cope, Syst. Catal. Vert. 

 Eocene New Mexico, p. 35 (not of Leidy). 



This is the most abundant species of the Bridger formation, and I 

 obtained parts of many individuals. Its characters are expressed in the 

 definition already given. To it must be added that the distal ends of the 

 costal bones are beveled regularly to the free rib-extremity. 



Almost the entire carapace of one of the individuals of this species was 

 obtained by myself in New Mexico. The pitting is uniform and without 

 interruption, extending even to the sutural edges of costal bones. It is 

 strong on the vertebral bones, but, near the distal ends of the costals, 

 becomes obscure ; the border itself being smooth. The ribs separating the 

 pits are coarse, but not so wide as the pits. 



The posterior part of the carapace of a Bridger specimen has the last 

 two pairs of costals in contact, showing that there were only six vertebral 

 bones. The pits are rather small, having, in some places, interspaces as 

 wide as themselves ; this is, however, not generally the case. The dividing 



