DERMATEMYDID&. 259 
Zygoramma microglypha Cope. 
Fig. 322. 
Zygoramma microglypha, Core, Proc. Amer. Philos. Soc., x11, 1871, p- 445 Vert. Cret. Form. West, 1875, 
p. 263.—Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p- 445. 
The remains described under the above name were found at Birmingham, New Jersey, 
in the uppermost stratum of Cretaceous greensand. They consisted of the greater part of the 
plastron and half of the carapace, with 4 peripheral bones, of an individual whose carapace 
must have had a length of about 600 mm. A portion of this material has been recognized in 
the Cope collection of reptiles, in the American Museum of Natural History, and this bears 
the number 6129. Unfortunately, up to the present time, no bones of the plastron have been 
found in the collection. No part of the species has hitherto been figured. 
The plastron is described as having a total length of 457 mm. According to Cope’s 
measurements, the length of the hyoplastron was 81 mm.; that of the hypoplastron, 145 mm.; 
that of the xiphiplastron, 117 mm. The length of the hyoplastron was probably taken along 
themidline. The front of the plastron 
was truncated. The width of the 
entoplastron was 95 mm.; its length 
something less; its thickness 11.6mm. 
The posterior border was truncated; 
the anterior border, regularly convex. 
; = The posterior plastral lobe was regu- 
Se ‘ ! ; larly contracted, and rounded, and it 
/ had a thin edge. Its width at the 
| hypoxiphiplastral suture was 220 
Gere mm.; the thickness at the midline, 
15.8 mm. 
The peripheral bones at the 
bridges are said to have had a thick- 
ened shoulder within, into which the 
‘S slender costal processes were received. 
The free peripherals were of lighter 
construction and somewhat everted. 
Most of the bones of the carapace 
that have been certainly identified are 
here figured (hg. 322). These consist 
of a portion of the first neural, the 
Fic. 322.—Z ygoramma microgly pha. Portion of carapace third and the fourth neurals, the prox- 
: of type. | XH. imal end of the first and third left cos- 
tals, parts or wholes of the second, 
third, fourth, and fifth right costals, 
and portions of other costals whose positions can not be determined. 
The first neural has a length of about 57 mm.; its width is 45 mm.; its thickness, 8 mm. 
The third and the fourth have each a median length of 60 mm. and a maximum width of 
37mm. Each is excavated in front for the preceding neural. Each has a thickness, where 
it joined the costal, of 1o mm. The first costal is 80 mm. wide; the second, 56 mm.; the third 
59 mm.; the fourth, 55 mm. On the lower side of the first there is the base of a strong rib- 
head, and in front of this a rough articulation for the first rib. The rib-heads of the other 
costals are very feebly developt. 
The sulci between the horny scutes are moderately distinct. The second vertebral had 
a length close to 105 mm. and a width about equal to the length. The first vertebral must 
have been considerably wider than the second. The third vertebral appears to have had a 
length of 115 mm. and a width close to 95 mm. 
As in Z. striatula, the marginal scutes extend high up on the distal ends of the costal bones, 
as may be seen from the figure. They pursue an irregular course. 
ime eal pes ae 
5 H 
» 
4 
C. p-1, C. p. 3, ¢. p. §, costal plates; m.1, 7.3, 7.4, neural bones. 
