TRIONYX. 113 



give a satisfactory answer, I have considered the specimen as characteristic of a new- 

 genus, for which the name of Botlu-emys is proposed in aUusion 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 faima of the Green- 

 sand formations of New Jersey has been greatly enriched. 



TRIOI%YX. 



Trionyx priscus. 



Trionyx priscus, Leidy, Proceedings Academy Natural Sciences, PMladelpliia, 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 fossU 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 aU 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 and 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 Trionyx. 

 The breadth at the trochanters is twenty lines; the diameter of the shaft just below 



15 April, 1865. 



