468 FOSSIL TURTLES OF NORTH AMERICA. 



ness of the portion occupied by the rib. Some of Cope's measurements appear to be slightly 

 erroneous. The thickness of the edge of the bone is nowhere quite 5 mm.; where thinnest 

 only 3 mm. The thickness thru the rib is a little less than 9 mm. 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 I 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. thomasi. Another costal does not show these. 



Figure 2 of plate 85 represents the right xiphiplastron. A comparison of this bone with that 

 of P. thomasi 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, COPE, Ann. Report U. S. Geol. and Geog. Surv. Terrs., 1873 (1874), p. 453; 



Bull. U. S. Geol. and Geog. Surv. Terrs., I, No. 2, 1874, p. 29; Vert. Cret. Form. West. 1875, pp. 94, 



261, plate vi, fig. 9. 



fPlastomenus punctulatus, COPE, Bull. U. S. Geol. and Geog. Surv. Terrs., HI, 1877, p. 573. 

 Plastomenus punctulatus, HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 453. HATCHKR, 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 Tnonvx 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 type locality was doubtful, because Cope, 

 in his latest description (Vert. Cret. Form. 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 Trionyt vagans, to his monograph, where 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. 



