145 



truncated at the extremity as in ordinary emydes. The back part likewise 

 has the same form as in the latter, and is also notched at the extremity. 



The pedicles are less elevated than in most recent emydes, and are rather 

 wider to the acute border of the carapace. 



The constitution of the plastron is so nearly like that of ordinary living 

 emydes as hardly to need special description. 



The entosternal plate is nearly lozenge-shaped, and is widest transversely. 

 The humeral scutes at their posterior border barely cross the posterior 

 extremity of the entosternal bone. 



The pectoral and abdominal scutes extend outwardly to conjoin the margi- 

 nal scutes upon the marginal bones. In ordinary recent species of Emys the 

 marginal scutes extend upon the hyosternal and hyposternal plates to join the 

 pectoral and abdominal scutes. 



The axillary and inguinal scutes are large, and impress each a marginal 

 and a sternal plate. 



The length of the carapace in a curved line is within half an inch of a foot 

 and a quarter; its breadth, in the same manner, 11 inches; in a straight line 

 it is little over a foot in length and about 10 inches in breadth. The plastron 

 is less than a foot in length, and its pedicles measure, fore and aft, 4^ inches. 

 5. The specimen originally referred to Emys Haydeni is represented in 

 Fig. 6, Plate IX. It consists of a portion of the carapace attached to a mass 

 of indurated clay, and was obtained near Fort Bridger, Wyoming, during Pro- 

 fessor Hayden's exploration of 1870. Since the specimen was figured, addi- 

 tional portions of the shell have been found which allow the restoration of 

 the fore part of the carapace. It belonged to a larger individual than the 

 specimen first attributed to E. Jeanesi, and from the appearance of the mar- 

 ginal border of several of the costal plates to a less mature one. 



The form of the carapace in front and its constitution in detail are very 

 similar to the corresponding portion in the former specimen attributed to E. 

 Jeanesi. The proportions of the vertebral plates is more nearly as in the lat- 

 ter than in the specimen attributed to E. Stevensonianus. 



An apparently important difference between the fossil under examination 

 and the one attributed to E. Jeanesi is the less uniformity of width of the 

 intermediate costal plates. These alternately become wider and narrower 

 toward their outer extremities, whereas in the specimen referred to E. Jeanesi 

 they are nearly uniform. 

 19 G 



