TRIONYX. 113 
give a satisfactory answer, I have considered the specimen as characteristic of a new 
genus, for which the name of Bothremys is proposed in allusion to the remarkable 
pits of the jaws. The species is dedicated to Prof. George H. Cook, of Rutger’s 
College, New Brunswick, New Jersey, by whom the specimen was obtained, and 
through whose explorations our knowledge of the vertebrate fauna of the Green- 
sand formations of New Jersey has been greatly enriched. 
TRIONYX. 
Trionyx priscus. 
Trionyzx priscus, Lewy, Proceedings Academy Natural Sciences, Philadelphia, 1851, V, 329. » 
A species of soft-shelled Turtle of the genus Trionyx appears to have existed 
during the deposit of the Green-sand formations of the United States, as indi- 
cated by the discovery of several small fossil fragments. These remains, if correctly 
referred to their true geological and zoological position, are the oldest of the genus, 
for no authentic species have previously been found in older formations than the 
Eocene Tertiary strata. But all existing Trionyces inhabit fresh water, and the 
extinct species heretofore described have been obtained from fresh-water deposits. 
The discovery, however, of remains of Trionyx in a marine formation like the 
American Green-sand does not prove that the genus inhabited the seas of the 
Cretaceous period. The species most probably, as at the present time, lived in 
rivers, down which the remains were carried to be deposited in, the Green-sand 
mud of the ocean. 
The museum of the Academy of Natural Sciences contains a small portion of a 
costal plate of a Trionyx, from the Green-sand of Burlington County, New Jersey. 
The fragment, together with its costal ridge, is nearly half an inch in thickness ; 
the plate away from the ridge is about three lines und a half in thickness. 
A more characteristic specimen is represented in Fig. 9, Plate XVIII. It con- 
sists of the outer portion of a costal plate, apparently the sixth of the left side, and 
measures two inches and a half long. It was found in the marl on the farm of G. 
C. Shenck, Monmouth County, New Jersey, and was sent to me for examination by 
Prof. Cook. At the broken border it is one inch and a half wide; at the outer 
border two inches. The costal ridge ends in a robust and comparatively short free 
process. The thickness of the plate, together with the costal ridge, internally is 
four lines, externally six lines; the thickness of the plate before and behind the 
ridge about three lines and a half. The free surface of the plate is covered with a 
network of ridges, of which those proceeding antero-posteriorly are very coarse, 
while the transverse connecting ridges are much finer. The meshes of the net- 
work are hemispherical pittings. 
Accompanying the specimens just described were two others, consisting of the 
acetabular portion of the pelvis and the upper extremity of the femur of the right 
side. The fragment of the femur, with the head mutilated, closely resembles in 
form the corresponding portion of the same bone in recent species of Trionys. 
The breadth at the trochanters is twenty lines; the diameter of the shaft just below 
15 April, 1865. 
