TRIONYCHID:. 5 13 
The sculpture of the carapace is coarse, and consists of deep pits of rather regular size, 
surrounded by walls which are as wide as the pits themselves. The figures of plate 97 show 
the general character of the ornamentation. The ridges which run across the costal plates are 
strongly developt, while the connecting ridges are less prominent. There are four rows of pits 
in about 15 mm. The sides of the pits rise more abruptly and the summits of the ridges are 
broader and more rounded than in 4. halophila. On the proximal ends of the costal plates, 
as shown by fig. 2, plate 97, the pits are arranged irregularly and vary much in size. 
The pits of the fragments of the plastron are smaller than those of the carapace and not 
so deep. 
Until more of the carapace of this species shall have been secured, we shall be uncertain 
as to its generic position. 
Amyda? halophila (Cope). 
Plate 96, figs. 4, 5. 
Trionyx halophilus, Core, Proc. Acad. Nat. Sci. Phila. 1869, p. 12; Cook’s Report Geol. New Jersey, 
1868 (1869), Append. 8, p. 735; Trans. Amer. Philos. Soc., xtv, 1869, p. 151, plate vu, fig. 155 
Vert. Cret. Form. West, 1875, p- 261.—Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 454. 
This species is said by Professor Cope to have been founded on numerous portions of the 
carapace and plastron, some from near Summit Bridge, New Castle County, Delaware, and 
some from Camden County, New Jersey. Whether or not these represented more than two 
individuals we are not informed. In the Cope collection of reptiles in the American Museum 
of Natural History there is a lot of bones, No. 1476, consisting of about 35 fragments of 
costals, neurals, and at least 1 piece of the plastron. With these is found Cope’s label, as 
follows: “Trionyx halophilus Cope. Type spec. Pits of Benj. Biggs, Summit Bridge, New 
Castle County, Del., 1867.” In George H. Cook’s Geology of New Jersey, p. 734, Cope 
states that in New Jersey this species comes from the lower marl bed of the Cretaceous. 
It is dificult to determine what meaning to attach to Cope’s use of the terms “Nos ts. 
“No. 2,” etc., in his table of measurements on page 152, of the Transactions American Philo- 
sophical Society, as cited above. Tt may mean that he had portions of 5 individuals, which ts 
the more probable conclusion. He speaks of having one costal plate which retained a portion 
of the head of one rib, and in the measurements he mentions it as “costal plate No. 1.” This 
fragment is yet in the collection, and is the one hgured by him; but it is not the first costal. 
His ‘‘centrum vertebra No. 2” is also present, but the shortness of the neural plate attacht to 
it, only 27 mm., appears to indicate that it is one of the posterior neurals. 
This species was a rather large one, the length of the carapace of the individual, or indi- 
viduals, represented by the remains before us, having probably been about 275 mm. The 
larger fragments of costal plates indicate that the carapace was considerably archt from side 
to side. The shell was quite thick and heavy; and the ribs stood out prominently on the under 
side of the distal ends of the costal plates. The thickness at the sutural border, at the outer 
end of one costal is 8 mm., while thru the rib it is 15 mm. The width of the costal at the 
outer end was at least 56 mm. On plate 96, fig. 4, 1s represented of the natural size a neural 
plate and a portion of a costal which belonged together. They are the same bones that Cope 
has figured. The greatest length of the neural 1s 37 mm.,; the greatest width, 35 mm.,; the 
thickness, 8 mm. The length of the fragment of costal is 60 mm.; its width, 33 mm.,; its thick- 
ness, at the costal margin, 7 mm.; at the middle of the width, 9 mm. The inner surface dis- 
plays the base of the rib-head. Cope states that his figure is half the natural size but, while 
the length of the figure of the piece of costal is slightly more than half the size of the original, 
the dimensions of the other portions are three-fifths of their natural size. Fig. 5 of plate 96 
represents a portion from the middle of the length of a costal plate. The right and left sides 
of the figure are the sutural borders. 
The neural plate which surmounts the centrum spoken of by Cope as “No. 2 ” is damaged 
somewhat, but it has had a length, in the midline, of 25 mm. and a width of 28 mm. The pos- 
terior border is convex, the anterior concave. 
The slight evidence afforded by one costal indicates that the free border was rounded 
off in section. The rib projected somewhat beyond the edge of the plate. 
33 
