250 FOSSIL TURTLES OF NORTH AMERICA. 
surface of the plastron appears to have been somewhat uneven, but no definite pattern of 
sculpture can be made out. 
The fourth neural (plate 37, fg. 5) has a length of 27 mm., a width of about 24 mm., and 
a thickness of 11 mm. The costals at the proximal ends are as thick as the neurals, but they 
rapidly become thinner, so that at a distance of 30 mm. from the neurals a costal is only 5.5 mm. 
thick; and this thickness is maintained to the distal ends. The capitula of the ribs are well 
developt. The sulci limiting laterally the vertebral scutes are deeply and sharply imprest. 
These vertebral scutes were Sather narrow, about 43 mm. wide. The third vertebral has a 
length of 60 mm. ‘The surface of the bone is finely striated longitudinally. 
Plate 37, fig. 4, represents 3 peripherals which appear to have had the positions assigned 
to them, the eighth, ninth, and tenth of right side, but possibly the ninth, tenth, and eleventh. 
The one seen on the right of the figure is the anterior, but it did not articulate with the 
hypoplastron. Each has an extreme thickness of about 11 mm. ‘The exterior surface is con- 
cave vertically, while the inner surface is strongly convex. Fig. 310 is a section through the 
middle one of the three. Altho the free edge of che series 1s somewhat eroded, it evidently was 
rounded. Further forward this edge appears to have been more angulated, until, as represented 
by one of the bridge peripherals, the upper side of the shell madel abruptly an angle of about 
45° with the lower side. The marginal scutes of this species were confined to the peripheral 
bones, instead of extending upward on the costals. As shown in the figures, the costal scutes 
come down well on the peripherals. 
The carapace of this species had a length of about 265 mm. 
In the Cope collection at the piensa Museum there is a pair of hyoplastrals, No. 1479 
(plate 37, fig. 2), which evidently belongs to this species and which is labeled as having been 
found at Mount Holly, New Jersey, in 1870. It has the size of 
the corresponding bones of the type, but it is considerably 
thicker, being 20 mm. just behind the entoplastral notch and 
also at the hinder border of the bones near the midline. About 
one-third the distance from the notch toward the rear the thick- 
ness is 22mm. This specimen displays the pectoro-abdominal 
pees. ; sulcus and a portion of the inframarginal scutes on the left 
IG. 310. A gomphus turgidus. “d Th ] i E h 4 b oS d é 4 ee 
Sethon Rage GE penphe side. e latter appear to have been arranged as in 4. pec 
eral of type. Xx. toralts. The median sulcus is obscure, but what appears to be 
a portion of it is seen on the right side running backward 
from the transverse sulcus, while apparently another short branch is seen on the left side. 
The surface of the plastron contains several large shallow pits and long grooves, as shown 
in the figure cited. It is evident that these have been made during the life of the animal, the 
result probably of some disease. Fig. 3 of plate 37 represents the same hyoplastrals seen from 
the front. 
Agomphus petrosus Cope. 
Plate 36, fig. 4; plate 37, figs. 6, 7; text-figs. 311-313. 
Adocus petrosus, Corr, Proc. Acad. Nat. Sci. Phila. 1868, p. 236; Cook’s Geol. New Jersey, App. B, 
1868 (1869), p. 734; Proc. Amer. Philos. Soc., x1, 1870, p. 295. 
Emys petrosus, Corr, Ext. Batrach., Reptilia, Aves N. A., 1869, pp. 125, 126. 
Agomphus petrosus, Corr, Proc. Amer. Philos. Soc., xu, 1871, p. 46; Ann. Report U.S. Geol. Sury. 
Terrs., 1872 (1873), p. 625; Vert. Cret. Form. West, 1875, p. 262.—Hay, Bibliog. and Cat. Foss. 
Vert. N. A.; 1902; p. 445. 
The type of this species is now a part of the Cope collection in the American Museum of 
Natural History in New York. It consists of a portion of the right hyoplastron; 5 peripheral 
bones, with perhaps a fragment of another; portions of four costal bones; a fragment of the 
right hypoplastron; and what Cope regarded as the head of the coracoid, but which seems to 
be rather the articular end of the pubis. These have been catalogged under the number 
1482. They were collected from the upper greensand bed of the Gretaceots, at Gloucester, 
New Jersey. 
The plastron (plate 36, fig. 4) was not flat below like that of the species of the other 
species of Agomphus, but very convex. Cope states that the curvature from the peripherals 
