468 FOSSIL TURTLES OF NORTH AMERICA. 
ness of the portion occupied by the rib. Some of Cope’ s measurements appcan to be slightly 
erroneous. The thickness of the edge of the bone is nowhere quite 5 mm.; where thinnest 
only 3mm. The thickness thru the rib is a little less than gmm. The Border of the plastral 
fragment is 10 mm. thick. The ornamentation of the surface of the costal is distinct and 
peculiar. There are about 5 of the angular pits in a line 10 mm. long. 
The fragment of the plastron appears to be a portion of the right hypoplastron extending 
from the inguinal notch backward. There are some indications that it extended to the xiphi- 
plastral suture. The free border is rounded. 
There are in the American Museum some portions of a carapace and a plastron which 
were collected by Mr. Barnum Brown in 1902, in Laramie deposits, 12 miles south of the 
Missouri River, on Hell Creek. The locality is 130 miles west of Miles City, Montana. It is 
not certainly known that the various bones belong to the same individual. Their number in 
the American Museum is 6131. Figure 1 of plate 85 represents the distal end of one costal, 
as seen from the upper surface. The thickness at the articular border is 5 mm.; that thru the 
rib is 8 mm. In this specimen, as in Cope’s type, the rib stands out on the lower surface of 
the bone with great distinctness. It likewise extended a considerable distance beyond the free 
border of the costal. These borders are beveled off obliquely to the upper surface. The 
ornamentation consists of a network of ridges, which anastamose irregularly and inclose pits 
and winding and interrupted valleys. The ridges are rather low, and there are from 4 to 6 
of them in a line 10 mm. long. On the costal plate here figured we find 2 welts crossing it, 
such as we find in P. thomas:. Another costal does not show these. 
Figure 2 of plate 85 represents the right xiphiplastron. A comparison of this bone with that 
of P. thomas: will reveal many similarities. There is no doubt that this bone articulated with 
the one of the opposite side thruout its entire length. At the anterior end of this median border 
there are two processes which entered pits in the opposite bone and received between them a 
process from that opposite bone. The anterior border also almost certainly articulated its full 
length with the hypoplastron. At the outer anterior angle there are two strong processes 
for digitation with the hypoplastron. At the base of these processes the thickness is 12 mm.; 
while at the median border the thickness is 5 mm. The sculpture of the bone agrees well with 
that of the portion of plastron described by Cope. It is similar to that of the carapace but the 
pits are not so deeply imprest. It covers the whole lower surface of the bone. 
Plastomenus? punctulatus Cope. 
?Plastomenus punctulatus, Copr, Ann. Report U.S. Geol. and Geog. Surv. Terrs., 1873 (1874), p- 4533 
Bull. U.S. Geol. and Geog. Surv. Terrs., 1, No. 2, 1874, p. 29; Vert. Cret. Form. West, 1875, pp. 94, 
261, plate vi, fig. 9. 
?Plastomenus punctulatus, Core, Bull. U.S. Geol. and Geog. Surv. Terrs., 111, 1877, p- 573: 
Plastomenus punctulatus, Hay, Buibliog. and Cat. Foss. Vert. N. A., 1902, p. 453.—Hatcuer, Bull. 
U. S. Geol. Surv., No. 257, 1905, p. 74 
Cope’s type of the present species consists of only a fragment of a costal plate, which the 
describer figured in his monograph on Cretaceous vertebrates, as cited above. This type is 
now in the American Museum and has the catalog number 1845. It was collected in north- 
eastern Colorado, in association with the type of Trionyx vagans Cope; and therefore on 
Bijou Creek, in deposits believed by Whitman Cross to belong to the Arapahoe formation. 
Professor Hatcher, as cited above, thought that the ty pe locality was doubtful, because Cope, 
in his latest description ( (Vert. Cret. Foam West, p. 94) says that the species was “‘established 
on a costal bone in association with the preceding species,” and the “preceding species” 
there is Plastomenus costatus, of the Judith River beds of British America. This comes from 
Cope’s having transferred without change his original description, which was preceded by 
his Trionyx vagans, to his monograph, w here it was ; preceded by Plastomenus costatus. There 
can be no doubt whatever that the present species was found on Bijou Creek, Colorado. The 
type is accompanied by a label in Cope’s handwriting as follows: “‘ Plastomenus punctulatus, 
10-9-1873, Colorado.” Cope states that he had examined several fragments of the same 
species that had been collected by Dr. Hayden at Long Lake, in the present state of North 
Dakota; but at present we can not depend on the determination. 
