DERMATKMYDID.*:. 



257 



The plastron has the extremities of the front and hinder lohes slightly elevated above the 

 portion between the bridges. The length is 211 mm. The anterior lobe is broadly rounded in 

 front; the posterior is short and pointed behind. The width of the anterior, on a line crossing 



at the hinder border of the entoplastron, is 102 mm.; its length 

 is 57 mm. The entoplastron is pointed in front, rounded behind, 

 42 mm. long and 46 mm. wide. The bridge has a width of 94 

 mm. The hinder lobe has a width, taken from the ends of the 

 abdomino-femoral sulci, of 88 mm. Its length is 57 mm. 



Some ot the sulci of the plastron are very obscure. Cope 

 was in doubt regarding some of those on the anterior lobe. One 

 sulcus crosses the entoplastron 37 mm. behind the front of 

 the lobe. Cope regarded this as the gulo-humeral ; the writer regards it as the humero-pectoral. 

 The area in front of this appears to the writer to be divided on each side into an intergular, 

 whose extent backward is doubtful, a small triangular gular, and a large humeral. Cope 

 appears to have been doubtful whether the sulcus behind the scutes, called by the present 

 writer gulars, continued directly across the front lobe, cutting off interwulars in front, or 

 turned backward and reacht the sulcus which crosses the entoplastron. 



Cope found evidences of a sulcus, his humero-pectoral, which commenct near the axillary 

 notch, ran forward parallel with the free border of the lobe, then turned inward and somewhat 

 backward, to cross the midline a little behind the entoplastron. The present writer, examining 

 the plastron without knowing Cope's determinations, did not observe such a sulcus. It is 

 not found on other species of Agomphus. 



According to the writer's determinations, the pectoral scutes join along the midline a 

 distance of 58 mm.; the abdominals, a distance of 26 mm. The femoro-anal sulcus appears to 

 be where drawn. Cope concluded that inframarginal scutes are present. The w T riter has no 

 doubt regarding this. 



Dr. George Baur (Zool. Anzeiger, XI, 1888, p. 595) stated that he had examined the 

 type of this species and regarded it as belonging to the genus Agomphus. He also informed us 

 that additional materials existed in the Yale University collection, but nothing further has 

 been heard of them. 



Genus ZYGORAMMA Cope. 



Characters, so far as known, those of Adocus, except that the hypoplastron sends no 

 buttress to the costals, but each sends a process into a pit between the seventh and eighth 

 peripherals. Bones of the carapace and plastron comparatively thin. Costals articulating 

 with peripherals by suture and gomphosis. Rib-heads feebly developt, except on the first 

 costals. Surface of carapace striated. Posterior marginal scutes rising on the costal bones 

 as in Adocus. 



Type: "Zygoramma striatula Cope. 



Zygoramma striatula Cope. 

 Plate 37, fig. jo; plate 38, figs. 1-3; text-fig. 321. 



Zygoramma striatula, Cope, Proc. Amer. Philos. Soc, XI, 1870, p. 550; Ibid, XII, 1871, p. 44; Vert. 

 Cut. Form. West, 1875, p. 263. Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 445. 



This species was based on rather fragmentary materials which were collected from the 

 upper greensand bed of the Cretaceous, at Pemberton, Burlington County, New Jersey. 

 The remains consist of the greater portion ot both hvpoplastra, 5 posterior peripherals, and 

 fragments of 3 costal bones. This type is in the American Museum of Natural History and 

 bears the catalog number 235S. 



The hvpoplastrals (plate 38, fig. 1) are thin, the thickness everywhere along the hyo- 

 hypoplastral suture present being only 6 mm. Near the midline, just in front of the suture 

 with the xiphiplastrals, the thickness is 7 mm., increasing to 9 mm. near the free border, 

 behind the inguinal notch. 



The sutures are coarse, each bone sending large teeth into pits of the other. These pits 

 and teeth belong to the deeper layers of the bone; while the sutures, as seen from below, 



