PLATEMYS. X09 



obliterated, or are so obscure as not to be traceable with any positiveness. The 

 median suture is irregular in its course, as were also those sutures which crossed 

 the sternum transversely. 



Though the hyosternal (5) and hypostemal plates (c) are of far greater extent 

 than in Emys firmus, they are absolutely very much thinner. The posterior angle 

 of the right hyosternal articulates across the median sternal suture with the con- 

 tiguous angle of the left hyposternal plate, which is provided with a tooth-like 

 process received into a corresponding pit of the former plate. 



The entosternal and episternal plates, judging from the forepart of the hyosternal, 

 appear to have had the arrangement seen in our common Terrapins. The breadth 

 of the entosternal space (a) between the hyosternal plates has been about two 

 inches and a half; its depth between the same plates about one inch and a half. 

 The estimated breadth of the sternum at the articulation of the epi- and hyosternals 

 has been four inches and a half. 



The length of the hyosternal plate along the median suture is four inches ; its 

 greatest length externally is five inches and three-quarters ; the width of its epi- 

 sternal suture is one inch and a half; and its thickness is nearly uniformly about 

 five lines. 



The length of the hyposternal plate along the median suture is five inches ; its 

 greatest length, a short distance outwardly, five inches and three-quarters ; and its 

 thickness ranges from five to seven lines. 



The xiphisternals (e, /) appear together to have been rounded off' posteriorly 

 and scarcely emarginate. 



PliATEMYS. 

 Plafeiuys sulcatum. 



Plalemys sidcatus, Leidt, Proc. Acad. Nat. Sci., Phila., 1856, VIII, 303. 



Three consecutive marginal plates of the left side of a carapace, found in asso- 

 ciation with remains of other Turtles in the Green-sand of Tinton Falls, Monmouth 

 County, New Jersey, and submitted to my inspection by Prof. George Cook, have 

 been referred to the genus Platemys, from no other character, however, than their 

 form. The plates articulated, as represented in Fig. 4, Plate XIX, are the fifth to 

 the seventh, inclusive. Their outer side inclines at an angle of nearly 45°, but 

 slopes in a gently curving manner more outwardly towards the thin acute basal 

 margin, which is wider posteriorly than anteriorly. The surface is feebly marked 

 with reticular furrows, and is grooved at the position of the borders of the 

 marginal and costal scutes. The grooves defining the costal and marginal scutes 

 cross the plates transversely just above their middle. The grooves defining the 

 marginal scutes laterally descend along the middle of the plates. The three bones 

 together, along the curve of their acute basal margin, measure eight inches. The 

 under side of the plates is broad and flat. 



With the marginal plates there was found a large fragment, apparently the 

 greater portion of a xiphisternal plate of the same individual. The under surface 

 exhibits the same kind of reticular furrows, as the marginal plates, but it is espe- 



