I MYDID^E. 



327 



i . rtevensoniana the maximum thickness of the first and second peripherals at their artic- 

 ulation is 14 mm.; in E. cyane, 17 mm. 



E. cyane differs from E. haydeni in the narrower inguinal buttresses, extending in the 

 former hardlv half-way from the free border of the hinder lobe to the midline; in haydcni more 

 than half-way. In E. cyane the thickness of the second neural is 11 mm.; in haydem, 14 mm. 

 The center of the plastron of E. cyane is 20.5 mm.; that of E. haydeni is 25 mm. Probably, 

 however, it will not do to relv too much on the relative thickness of the neurals and of the 

 plastron. E. cyane has wider vertebral scutes than E. haydeni, and the fourth neural is 

 not octagonal. 



Echmatemys shaughnessiana (Cope). 

 Plate 50, figs. 1, 2; text-figs. 428-4^1. 



Emys shaughnessiana, CoPE, Amer. Naturalist, xvi, 1882, p. 992; Vert. Ttrt. Form. West, 1884, pp. 

 I }0, 1 ^5, plate xxiii, figs. 3-8. Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 448. 



This species was first mentioned in 1882, but the only statement made regarding it by 

 Professor Cope is that its bones are very thick. In 1884 a description was pubhsht, illustrated 

 by figures of the carapace. No part of the plastron was figured. The specimen was tound in 



Figs. 428431. Echmatemys shaughnessiana. Carapace and plastron ot type. 



428. Carapace. Xj. Parts restored are shown by interrupted lines. 



429. Plastron. Xj- 4^0. I'pper surface of front lobe of plastron. Xl- 

 431. Tpper surface of border of hinder lobe of plastron. XI. 



the Brido-er deposits of Wyoming, in 1872, on Cottonwood Creek, therefore about the middle 

 of stage B. 



The type of the species is now in the possession of the Museum of Natural History and 

 bears the number 1069. A further description is here turnisht as well as figures of both cara- 

 pace and plastron. This is the more to be desired, since some of Professor Cope's measure- 

 ments are found to be incorrect. 



Professor Cope recognized that this species resembles in many respects Dr. Leidy's 

 E. wyominttnsis; and he has given what he regarded as differential characters. In general. 



