EOOl^NE TESTUDINATA. 
57 
Emys cibollensis, Cope. 
Plate xxvii, fig. 4; Plate xxviiL, figs. 3-6. 
Emys ? Stevensonianus, “Leidy,” Cope, System. Cat. Vertebrata Eocene New Mexico, 
U. S. Geog. Survs. W. of lOOtb M., 1875, p. 36. 
This species is represented by the imperfect carapace and plastron of 
a single individual, in which some of all the characteristic elements are 
present, excepting the vertebral bones. The general relationships of the 
species are to the Emys lativertebralis, that is, the anterior lobe of the plastron 
has a distinct truncate lip, and the posterior lobe is deeply excavated on the 
middle line; the superior borders of both lobes have a thickened band, 
which is best developed posteriorly; and the costal and marginal bones are 
without especial sculpture. 
The specimen is below the average size of those of the E. lativertebralis, 
but not sufficiently so to account for the much smaller size of the marginal 
bones, which are also relatively thicker. The lobes of the plastron are dif¬ 
ferently proportioned. Thus, in E. lativertebralis, the posterior lobe, measured 
along the median line, is as long as the anterior to the j^osterior suture of 
the mesosternal bone; in the E. cibollensis, the former measurement consid¬ 
erably exceeds the latter. This shortening of the anterior lobe of the plas¬ 
tron is accompanied by other peculiarities. The mesosternum is transverse 
diamond-shaped, the posterior border being nearly as angular as the ante¬ 
rior. The dermal scuta have an anterior position. The gulars are very 
short, each one being wider than long, and their posterior angle not reach¬ 
ing the mesosternum. The humero-pectoral scutal suture, on the other 
hand, crosses the mesosternum a little behind the middle, instead of passing 
behind it, as in E. lativertebralis. The thickening of the margins of the plas¬ 
tron has some low ribs parallel to the border. The osseous sutures are not 
very coarse; the dermal sutures well marked. The marginal bones are not, 
or but little, recurved. The lip of the plastron has a slight notch on one 
side. 
Measurements. 
M. 
Anteroposterior width of a costal bone. 0.022 
Thickness of the same. 0.006 
Length of a posterior free marginal...... . . 0.030 
Thickness of the same. - . 0.009 
