DERMATEMYDIDyE. 



255 



The materials possest by Leidy when he described this species consisted of the third, 

 sixth, and the seventh left peripherals, the sixth, seventh, and eighth peripherals of the right 

 side, a portion of the left hyoplastron, and a portion of the right hypoplastron. These had 

 been placed in Dr. Leidy's hands by Professor George H. Cook, of the New Jersey Geological 

 Survey. They had been found in the uppermost Cretaceous greensand, at Tinton Falls, 

 Monmouth County, New Jersey. The sixth and seventh left peripherals and the parts of the 

 plastron were figured by Leidy, as cited above, and these are now in the State collection 

 at Rutgers College, New Brunswick, New Jersey. The peripherals mentioned by Leidy are 

 not in this collection at present. 



For figures of the scanty remains forming the type the reader is referred to Leidy's paper 

 in the Smithsonian Contributions cited in the synonymy. 



The length of the figured peripherals is 140 mm. The height of the seventh is 93 mm. 

 The costo-marginal sulcus crosses these peripherals between the upper and middle thirds. 

 This shows that the species does not belong to Adocus. 



The left hyoplastron has a length of 80 mm., altho its length along the median suture is 

 somewhat less. The hypoplastron had a length of 85 mm. but only 65 mm. at the midline. 

 As shown by Leidy's figure, the hypoplastron articulated both in front and behind with the 

 bones of the opposite side, a condition not unusual with the members of the family. The 

 thickness of the hyoplastron at the midline and just behind the entoplastron is 26 mm. The 

 greatest thickness of the hypoplastron is 19 mm. 



The excavation in the front of the hyoplastron shows that the entoplastron was truncated 

 behind and that its width was about 65 mm. The pectoro-abdominal sulcus crost the hyo- 

 plastron somewhat in front of the middle of its length; while the abdomino-femoral crost 

 the hypoplastron about the middle of its length. 



This species, known up to the present time from only the type specimens, differs from all 

 the other described species of Agomphus in having the entoplastron truncated behind and in 

 having the pectoro-abdominal sulcus cross nearer the entoplastron than to the hinder border 

 of the hyoplastron. 



Agomphus masculinus Wieland. 

 Fig. 319. 



Agomphus masculinus, WIELAND, Amer. Jour. Sci. (4), xx, 1905, p. 437, fig. 8. 



The type of this species belongs to the Marsh collection at Yale University Museum and is 

 numbered 671. It consists of the complete plastron and some portions of the carapace, includ- 

 ing some of the hinder peripherals. It was collected 

 in the Upper Cretaceous marl bed at Barnesboro, 

 Gloucester County, New Jersey, in 1872. 



The plastron (fig. 319) resembles closely that of 

 A. turgidus, so far as the latter is represented. Dr. 

 Wieland has mentioned one character which differ- 

 entiates the carapace from that of Cope's species just 

 mentioned. In A. masculinus the eleventh and 

 twelfth marginal scutes overlap the lower ends of 

 the eighth costal bone and the suprapygal; whereas 

 in A. turgidus these marginals do not rise above 

 the peripherals. This appears to be a sufficient 

 specific distinction. 



The length of the plastron is 170 mm.; the 

 extreme width, 130 mm. The anterior lobe narrows 

 rapidly from the base to the blunt tip. The width 

 of the base of the lobe is about 92 mm.; the length, 

 41 mm. The epiplastrals are narrow. The ento- 

 plastron is subrhombic, 33 mm. long and 36 mm. 



FIG. 319. Agomphus masculinus. Plastron w ' d e- Its thickness is 15 mm. The other plastral 

 of type. XL Redrawn from Wieland's bones are unsymmetrical, as is common among the 

 figure. older turtles. The left hyoplastron joins the right 



