488 FOSSIL TURTLES OF NORTH AMERICA. 
Small, shallow, rounded depressions mark the surface of the neurals and the inner ends of the costals. 
In the latter, as the distance from the neurals increases, the depressions gradually grow larger and more 
decided, becoming often reniform or oval, and frequently coalescing, until in the distal ends of the costals 
a few more or less continuous furrows are formed parallel to the outer margins of the plates. ‘These 
furrows are a conspicuous feature in the sculpture; they are not so well marked on the posterior margin 
of the carapace, but are well developed near the front edges of the first costals. In the neurals and 
inner halves of the costals there is a narrow, smooth strip, devoid of all sculpture, bordering the sutures. 
None of the plastral bones referred by Lambe to this species were associated with the 
carapace described. The author referred to states that the plastral bones belonged to individuals 
of larger size than that to which the carapace belonged. A comparison of the bones with 
corresponding parts of individuals belonging to Platypeltis ferox and P. spinifera shows that 
the individual represented by the carapace may have been as large as the others or even larger. 
In form the plastron (plate 89, fig. 2; text-fg. 644) resembled much that of the living 
species just mentioned. ‘The sculpture consists of ridges and intervening furrows of varying 
length and of irregular direction. 
Of the ridges there are about 9 
33 in a line 20 mm. long. On the 
ae a: outer ends of the bones the ridges 
run parallel with the long axis of 
Z the animal. On the inner half, 
{ the ridges are shorter, less eleva- 
hyo \ ted, and irregular in their course. 
, In the collection of fossil verte- 
brates made in the Judith River 
basin by Mr. C. H. Sternberg, in 
1876, for Professor Cope, fiere 
are many fragments of costal 
bones which belongtothis species; 
but they throw no adderall light 
on it. 
From the Laramie beds at Hell 
Fic. 644.—Asprderetes foveatus. Right Hyoplastron and hypo- Creek, Montana, Mr. Barnum 
plastron. %%. Reduced fein Lambe’s figure. Brown has brought to the Amer- 
ican Museum of Natural History 
fragments of a trionychid that 
resemble very closely similar poemene from the Judith River basin. Three consecutive 
neurals and portions of costals have the number 1017. Had they been found in Judith River 
deposits they would without hesitation be referred to 4. foveatus. Perhaps only the finding 
of a complete shell of this Laramie form will settle the questions involved. 
The character of the sculpture, especially that of the central regions of the carapace, 
distinguishes 4. foveatus from any other of the Judith River species with which it is likely to 
be compared. 
The specimens of Trionyx foveatus cited by Prof. O. C. Marsh as having been found in 
the Ceratops beds near Denver, Colorado, belong probably to 4sprderetes eee hers but the 
present writer has not seen the materials on which Marsh’s statement was founded. 
hypo 
hpo, hyoplastron; hypo, a 
Aspideretes coalescens (Cope). 
Plate 88, fig. 6; plate go, fig. 1; text-fig. 645. 
Plastomenus coalescens, Cort, Proc. Acad. Nat. Sci. Phila. 1875, p. 9 ine description); Brit. N. A., 
Bound. Comm. Report on Geol. and Resources 49th Par., 1875, p. 337; Vert. Cret. Form. West, 
1875, pp- 93, 261, plate viii, igs. 6, 7—LamBE, Ottawa Naturalist, X11, 1899, pp- 68, 70; Summary 
Report Geol. Sury. Canada, 1808 (1899), p- 182- 190.—HaTcuer, Bull. U. S. Geol. Surv. No. 257, 
1905, p- 74 
Trionyx vagans, ?Core, Bull. U.S. Geol. Surv. Terrs., m1, 1877, p. 573.—Lamse, Contrib. Canad. Pal- 
wont., HI (4 to), 1902, p. 36, plate 1, figs. 3, 4, text- fig. 2: 
Trionyx coalescens, Hay, Billions and Cat. Foss. Vert. N. A., 1902, p. 454. 
Plastomenus (Trionyx) ee ed Osrorn, Contrib. Canad. Paleonts rt (4 to), 1902, pp. 12 
