EMYDIDjE. 



313 



] mm. wide, and it is transversely concave. In the figure this surface is shaded by horizontal 

 lines. The height of the bone is 7 mm. and the thickness nowhere exceeds 3.5 mm. 



The right humerus of No. 5968 is preserved. The head is not globular, but consists of a 

 broad ridge, whose axis makes a small angle with the shaft of the bone, and a groove on the 

 radial side. The whole structure is exactly like that of the humerus of the species otTrachemys. 



No. 6010 was collected on Little Dry Creek, Wyoming, and therefore belongs to horizon 

 B. It is represented by only the plastron. Fig. 400 shows the upper side of the anterior lobe 

 and fig. 401 the beveled surface of the hinder lobe. Both in front and behind, the beveled 

 horn-covered surfaces are wider than in No. 5988. These figures represent the condition found 

 in a certain number of specimens that must be referred to this species. 



Figs. 402 and 403 represent a remarkable specimen which belongs to the Yale University 

 Museum. It was collected by one of Professor Marsh's parties in 1874, in the Bridger Eocene, 

 near Millersville, Wyoming. It was described in the American Journal of Science by Hay, 

 as cited above. It is interesting because of the presence of one extra neural, two extra pairs of 

 costal plates, one extra pair of peripherals, an extra vertebral scute, an extra pair ot costal 

 scutes, and an extra pair of marginal scutes. These supernumerary structures are not regarded 

 as of even specific value. It is to be observed, however, that the anterior lobe of the plastron 

 narrows more rapidly than usual and that the base of the hinder lobe is wider than usual; is, 

 indeed, more than half the length of the plastron. 



Two specimens in Princeton University are referred to E. wyomingensis. These are 

 numbered 10071 and 10072. In both of these the axillary and the inguinal buttresses extend 

 inward but little beyond the free borders of the bases of the plastral lobes. In this respect 

 these specimens differ greatly from those of E. haydeni, to which they might easily be referred. 

 Like the latter species, No. 10071 has the fourth neural octagonal, while No. 10072 has this 

 neural heptagonal. 



Figs. 404-406. Echmatemys haydeni. Carapace and plastron. X}. 



404. Portion of carapace of type. U.S.N.M. 405. Portion of carapace. No. 1067 A. M. N. H. 



406. Plastron. No. 1067 A.M.N. H. 



Echmatemys haydeni (Leidy). 

 Plate 47, fig. 2; text-figs. 404-410. 



Emvs haydeni, Leidy, Proc. Acad. Nat. Sci. Phila. 1870, p. 123; Ann. Report U. S. Geol. Surv. Wyoming, 

 etc., 1870 (1871), p. 366. Cope, Vert. Tert. Form. West, 1884, p. 137. Hay, Bibliog. and Cat. 

 Foss. Vert. N. A., 1902, p. 448. 



Emys wyomingensis, Leidy, Ann. Report U. S. Geol. Surv. Montana, etc., 1871 (1872), p. 367 (in part); 

 Contrib. Ext. Fauna West. Terrs., 1873, p. 145 (in part), plate ix, fig. 6. 



