528 FOSSIL TURTLES OF NORTH AMERICA. 
25 
deposits of New Mexico. His figures represent fragments of 3 costal plates. He states that 
the species is readily distinguisht by the closely placed subparallel ridges which cross the ribs 
parallel to the axis of the body and which are separated by one or two rows of imprest dots, 
or small fossz. 
The costals varied in width from 18 mm. to 27 mm. and in thickness from 3 mm. to 5 
mm. Three and a half ridges occupied a space of 9 mm. 
The American Museum of Natural History expedition of 1903 to the Bridger beds in the 
region about Fort Bridger, Wyoming, secured a large portion of the carapace and a consider- 
able part of the plastron of a specimen which it appears necessary to refer to Cope’s Wasatch 
species. When, however, more satisfactory materials of the latter have been secured, it may 
Bre that the Bridger remains belong to an unnamed species. 
Cope’s assignment of his materials to the genus Plastomenus depended on no part of the 
plastron, and was therefore inconclusive. There is reason to believe that the Bridger speci- 
men does not belong to Plastomenus, but must be assigned to Platypeltis. It bears the cata- 
log number 6014. 
Of the individual here described (plate 98, fig. 13) there are present most of the first 
neural and the whole of the third; practically all of ihe 6 anterior costal plates, and a fragment 
of the seventh; the mesial half of the right hyoplastron and hypoplastron; and Somewiae. more 
of the mesial half of the same bones of the left side. 
It is evident that the nuchal of this individual had no sutural connection with the costals 
of the anterior pair; whether or not it had such connection with the first neural is made doubt- 
ful by the fact that the anterior portion of this bone is missing. The hinder border of the 
carapace being gone, as well as the nuchal, the length can not be determined. From the front 
of the first costal to the hinder border of the sixthis 95 mm. Judging from the curve of the free 
borders of the sixth costals, but a few millimeters, perhaps 10 mm., would have been added 
by the seventh costals. If now we add 10 mm. as the width of the nuchal, we shall have as 
the probable length of the carapace 105 mm. ‘The width of the disk is t00 mm. How far the 
ribs projected beyond the disk can not be determined. 
The first neural had a length of about 16 mm. and a width of 13 mm. The third has the 
same length, but 1s 12 mm. mide! Both are of hexagonal form, with the narrow end directed 
forward. The sixth neural was also of the same form, but had the narrow end directed back- 
ward. ‘There was present a small seventh neural wedged in between the costals of the sixth 
and seventh pairs. 
The third costals are 17 mm. wide near their outer ends, 3.5 mm. thick near the sutural 
borders, and 5 mm. thru the rib. Toward the outer ends of the costals the ribs become quite 
prominent on the inner surfaces of the former. 
The ornamentation of the carapace agrees with that of Cope’s Plastomenus serialis. 
There are on each side about 7 longitudinal ridges, or welts. These are low on the front of the 
shell but much more prominent posteriorly. Five of these ridges cross the sixth costal. Be- 
tween the ridges there are from 1 to 3 rows of pits of varying sizes. On the neurals there are 
only small pits, or puncte. 
The plastron of this specimen, so far as represented, was like that of Platypeltis spinifera. 
The width of the hyoplastron (plate 109, fig. 3), where narrowest, is 7 mm.; that of the hypo- 
plastron at the same place, is 10 mm. ‘The inner end of the former bone expanded into a 
single flat process; that of the hypoplastron into two such processes. A callosity of 15 mm. 
wideh occupied these bones along their common suture, about half of it on each bone. 
No. 5944 of the American Mitisedea of Natural History, a specimen collected at Grizzly 
Buttes, Wyoming, in 1903, is referred to this species. It consists of portions of the carapace, 
the right hyoplastron and hypoplastron nearly complete, the median halves of the same bones 
of the] left side, portions of the pectoral and pelvic g cirdles, and parts of the humerus and femur. 
These belonged to an older and larger individual than the one just described. The carapace 
(plate 109, fie. 4) 1s remarkable for the strong development of the longitudinal ridges; but it 
is not believ ed that a distinct species is indicated. One fragment belongs to the hinder rm 
of the carapace, and presents the seventh and eighth costals of the right side. The eighth 
costal was small. The plastron (plate 109, fig. 2; text-fig. 694) is in a more advanct stage of 
