DERMATEMYDID&. 257 
The plastron has the extremities of the front and hinder lobes 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 57mm. 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 of 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 intergulars 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 4 gomphus. 
According to the writer’s determinations, the pectoral scutes join along the midline a 
distance of §8 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 writer has no 
doubt regarding this. 
Dr. George Baur (Zool. Anzeiger, x1, 1888, p. 595) stated that he had examined the 
type of this species and regarded it as belonging to the genus 4gomphus. He also informed us 
that additional materials existed in the Yale University collection, but nothing further has 
been heard of them. 
Neural. Length. Width. 
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Genus ZYGORAMMA Cope. 
Characters, so far as known, those of 4docus, 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. 10; plate 38, figs. 1-3; text-fig. 321. 
Zygoramma striatula, Corr, Proc. Amer. Philos. Soc., x1, 1870, p. 5503 Ibid, xu, 1871, p. 44; Vert. 
Cret. 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 of both hypoplastra, 5 posterior peripherals, and 
fragments of 3 costal bones. This type is in the American Museum of Natural History and 
bears the catalog number 2358. 
The hypoplastrals (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 le 
with the xiphiplastrals, the thickness is 7 mm., increasing to g9 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, 
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