ESTUDINIDZ&. 409 
following description is taken from No. 1139. All the known specimens were collected in the 
White River deposits (Oreodon beds), at the head of Horse Tail Creek, in northeastern 
Colorado. 
The members of this species appear to have had a rather narrow and elongated shell; 
and this was probably considerably elevated. The form was therefore somewhat like that of 
Stylemys oregonensts or that of the living Testudo tabulata. 
The length of the carapace was close to 460 mm., and the width approximately 3 300 mm. 
The anterior part of the carapace which has been preserved (hg. 526) consists of a portion of 
the left first peripheral, nearly the whole of the nuchal, the first, second, and most of the third, 
right peripherals, and a part of the first right costal. The anterior border is somewhat concave 
along the nuchal and part of the first peripheral; then it passes by a broad curve into the side. 
The free edge of this rim is subacute, but it is considerably roughened. The nuchal is 76 mm. 
wide along the free border; 126 mm. in maximum width, and about 100 mm. along the median 
line. Its greatest thickness at the midline is 25 mm. The border of the first peripheral i is 77 
mm. long; that of the second is 75 mm. The anterior peripherals are but little flared. 
The bridge peripherals preserved (fig. 527) are part of the fourth, most of the fifth, sixth, 
and seventh. Each was about 50 mm. wide and 110 mm. high. A rather deep groove runs 
along the side of the shell just above the lower ends of these peripherals. 
The posterior peripherals (fig. 527) and practically the whole of the pygal (fig. 528) are 
present. The free edges of all these are acute. The tenth and the eleventh flare slightly. 
The eighth is 80 mm. high; the eleventh, 63 mm. The thickness of each is about 22 mm. 
The inferior surface is convex in perpendicular section. The pygal is convex above in all 
directions. The upper border is 80 mm. wide and somewhat excavated for the second supra- 
pygal; the free border is only about 25 mm. wide. The thickness is 17 mm. The second 
suprapygal is broadly triangular, with a repand base. The height is 50 mm., the width 80 
mm. The penultimate suprapygal (hg. 528) has the usual bifincate form, with the forks 
resting on the eleventh peripherals. The hinder portion of the carapace has sloped downward 
and backward at an angle of about 45°. 
The fourth costal had a width of about 60 mm. at its lower end; the fifth, a width of 34 
mm.; the sixth, a width of 49 mm.; the seventh, a width of 33 mm.; the eighth, a width of 
44mm. The costals have a thickness of about 8mm. No neurals have been preserved. 
The sulci which limit the dermal scutes of the carapace are usually narrow and only 
slightly imprest, that passing between the costals and the marginals being broadest and 
deepest. 
The nuchal scute is 36 mm. long and 16 mm. wide. The first marginal is 53 mm. along 
its anterior border and 81 mm. along the hinder, an unusual form. The second is 77 mm. 
wide along the free border; 30 mm. along the posterior border. The third has a width of 69 
mm. along the free border. The first vertebral had a width of 146 mm. across the anterior 
end, but acrewee posteriorly. The hinder end of the fifth had a width of about 80 mm. 
Since most of the median region of the carapace is missing, nothing is to be learned regarding 
the other vertebrals. 
The height of the supracaudal scute (fg. 528, sc) is 73 mm.; its width 100 mm. Its upper 
border rises on the second peripheral about 20 mm. 
As already stated, only the anterior half of the plastron of No. 1139 is present. Nor is 
there at command any plastron which furnishes both the hinder and the anterior portions. 
It is hence impossible to determine exactly the length of this portion of the shell. The length 
of the anterior half of No. 1139 (fig. 529, front portion), to the hyohypoplastral suture, is 238 
mm. The length of the hinder portion of the type plastron figured by Cope (fig. 529, hinder 
portion), measuring backward from the hyohypoplastral suture, is 256 mm. This applied to 
the anterior half of 1139 would bring the hinder border too close to the pygal and therefore 
must have belonged to a somewhat larger individual than the latter. About 220 mm. may be 
added to the length of the anterior half of 1139, thus making its plastron 458 mm. long. This 
implies that the anterior lip must have projected somewhat in front of the anterior border of 
the carapace, and this conclusion has been reacht on other grounds. 
The anterior lobe of No. 1139 has a length of 165 mm. and a width of 214 mm. The free 
edge is acute, except at the midline, where it is somewhat rounded. The anterior lip does not 
