EMYDIDZ. 313 
3 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 a Trachemys. 
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 Seiehice 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 of 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; 
indeed, more than half the length of the plastron. 
6 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 £. haydenz, 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. 
“ae 
Fics. 404-406.—Echmatemys haydent. Carapace and plastron.  }. 
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. 
Emys haydent, Lewy, 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 wyomtngensts, Lerpy, Ann. Report U.S. Geol. Sury. Montana, etc., 1871 (1872), p. 367 (in part); 
Contrib. Ext. Fauna West. Terrs., 1873, p. 145 (in part), plate ix, fig. 6. 
