124 THE WASATCH AND JJKIDGKR FAUNJE. 



■clearly, and find portions of another individual from another locality to 

 pertain to the same. 



The sculpture of the costal bones consists of reticulated ridges which 

 inclose coarser pits than in the next species, and show no tendency to run 

 into ribs extending obliquely acrossthe bones. The first costal exhibits a 

 greatly beveled suture for the nuchal, and its alar portion behind its costal 

 rib is twice as wide as the latter. The last costal differs from that of P. 

 thomasii in being angulate instead of truncate at the rib-extremity, and the 

 latter projects strongly beyond the angle. 



The sculpture of the costal bones is somewhat like that of Trionyx scu- 

 tumantiquum. It can hardly be regarded as the young of that species, for, 

 although of small size, the complete ossification of the costal bones indicates 

 that the specimens are of mature age. 



Bad lands of Cottonwood Creek, near Fort Bridger, Wyoming. 



Pj.astomenus multifoveatus Cope. 



Anim.al Keport U. S. Geol.'Surv. Terra., lt<72(187.'?), p. G19. Report U. S. Geo. Geol. Siirv. W. of 100th 

 Jlcr., iv, pt. ii, p. 49. P. thomasi p.irs. Annual Report U. S. Geol. Surv. Terrs., 1872 (1873), p. C18. 



Plate XVII, figs. 2-8. 



Represented by various parts of four individuals, a sufficient number 

 of identical pieces being present in all to insure their specific unity. The 

 bones of both carapace and plastron have a honeycomb pattern of reticu- 

 lation, with shallow pits, which on weathering become punctaj. The 

 intervening ribs tend to connect into ridges running diagonally across the 

 costal bones. The pits tend to form linear series parallel to the bordei-s, 

 on some of the bones of the plastron. The latter are gently convex at the 

 transverse suture. The last costal is very wide, and is in contact with its 

 fellow on the median line as in other species of the genus, except .a sutural 

 margination behind, apparently for a pygal bone. The outer border is 

 straight, truncating the last rib-extremity. 



Meaatircmcnts. 



M. 



Thickness of a costal 004 



Wiillli luHt eostal, iliHtally 04(J 



Wiiltli of liyostemal 018 



TliiikiH'HH of liyosternal 005 



Lengt li of a vertebral 018 



Width of a vertebral 014 



