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 ^j, fig. 5) has a length of zj mm., a width of about 24 mm., and 

 a thickness of 1 1 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 rather 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 1 1 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 the series is 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 made 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 American 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 22 mm. This specimen displays the pectoro-abdominal 



v- 4i 1 sulcus and a portion of the inframarginal scutes on the left 



rlG. 310. Agomphus turgidus. . . . r . . & . . . 



Section across ninth periph- S,de ; . e , la er appear to have been arranged as in A. pec- 

 eral of type. X a tor alts. 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 ^y represents the same hyoplastrals seen from 

 the front. 



Agomphus petrosus Cope. 



Plate 36, fig. 4; plate 37, figs. 6, 7; text-figs. 31 1-313. 



Adocus petrosus, C'opk, Proc. Acad. Nat. Sci. Phila. 1868, p. 236; Cook's Geol. New Jersey, App. B, 



1868 (1869), p. 734; Proc. Amer. Philos. Soc, xi, 1870, p. 295. 

 Emys petrosus, Cope, Ext. Batrach., Reptilia, Aves N. A., 1869, pp. 1 25, 1 26. 

 Agomphus petrosus, Cope, Proc. Amer. Philos. Soc, xn, 1871, p. 46; Ann. Report U. S. Geol. Stirv. 



Terrs., 1872 (1873), p. 625; Vert. Cret. Form. West, 1875, p. 262. Hay, Bibliog. and Cat. Foss. 



Vert. N. A., Kin), 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 Cretaceous, 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 



