DERMATEMYDID&. 237 
type belongs to the Marsh collection in Yale University Museum and presents the nearly 
complete shell. It was obtained in the upper bed of Cretaceous marl at Hornerstown, Mon- 
mouth County, New Jersey, in 1872. It has been restored and fully described by Dr. G. R. 
ae Wieland, as cited in the synonymy. Dr. 
Wieland’s figures are employed in the pres- 
ent work to illustrate the structure. 
The total length of the carapace (plate 
35, fig. 1; text-fig. 296) ina straight line is 
533 mm. The greatest width is 390 mm. 
The form is that of an elongated oval, 
broadest behind the middle, rounded in 
front, more broadly rounded behind. Dr. 
Wieland has called attention to a double 
curvature along the sides. Possibly this 
is due to slight distortion. From side to 
side anteriorly the carapace is quite evenly 
convex; posteriorly in the restoration it is 
somewhat flattened. The hinder periph- 
erals are flared somewhat upward, but the 
front ones are not. The peripherals of the 
free borders are thin and reduced to an 
acute edge. In front of the axillary notch 
the edges of the peripherals are somewhat 
reverted, leaving a groove within the edges. 
The nuchal bone is 70 mm. long on the 
midline; 65 mm. wide on the free edge; 95 
mm. where widest. There were 7 neurals, 
of which all are present except the sixth. 
Its form and dimensions are determinable 
from the surrounding bones. The seventh 
was not developt; the eighth is small. The 
Fic. 296.—Adocus punctatus. Carapaceof type. X0.18. table below presents the dimensions of the 
c.p.1,c. p.2,c. p.8, costal plates; m.s.1,m.s.12,marginal scutes; neurals. 
nu. p, nuchal plate; per, 2, per, 11, peripheral bones; py, Most of the neurals are hexagonal, 
pygal; spy, suprapygal; n.1, 2.6, neural bones. with the broader end forward. The first 
has the broader end behind; the second is octagonal. The absence of the seventh neural 
permitted the seventh pair of costals to meet in the midline. Those of the eighth pair also 
meet in the midline in front of the eighth neural. The single suprapygal is octagonal, 70 
mm. long and 110 mm. wide. 
The peripherals are in general large. Their height, at right angles with the free border, 
increases from the third to the ninth; the tenth has nearly the height of the ninth; the eleventh 
is considerably smaller. The first peripheral extends along the free border 63 mm.; and 
from this to the first costal, 65 mm. The second is slightly smaller in both dimensions. The 
third occupies 50 mm. of the free border and is 65 mm. high. The ninth is 75 mm. along the 
free edge and 103 mm. high. The eleventh occupies 62 mm. of the free border and rises 
toward the suprapygal 70 mm. The pygal measures 65 mm. 
along the free edge and is 60 mm. high. 
Neural. | Length. = Width. The sulci are usually rather narrow and shallow. Those 
ee a on the front are somewhat deeper and broader. The table on 
page 238 gives the dimensions of the vertebral scutes. 
38 
| ; 4 27 The costal and the marginal scutes are of unusual confor- 
3 Ss? pie mation. The anterior marginals are mostly small; the lateral and 
i 38 posterior remarkably large. As a result, most of the costals are 
6 44 35 considerably reduced in area. The nuchal scute is 16 mm. long 
aa > and only 6 mm. wide. From this the marginals continue to rise 
slowly above the free border to the hinder end of fourth, which 
