148 



13. A specimen, apparently of a still younger individual of the same species, 

 presented to the writer by Dr. Carter, was about the size of the palm of the 

 hand. It consists of small portions of the carapace and more than half the 

 plastron. The carapace is carinated as in specimen No. 11, and otherwise 

 agrees with this in its details. The plastron has the same form as in the 

 more complete and older specimens previously indicated, but the entosternal 

 is more pyriform, considerably longer than wide, and the posterior denning 

 groove of the pectoral scute crosses its middle. 



If it is admitted that the specimens Nos. 11 and 13 belong to Emys 

 wyomingensis, it would appear that the carinated condition of the carapace is 

 a juvenile character, disappearing with growth. It would also appear that 

 during growth the breadth of the entosternal plate became proportionately 

 greater in relation with its length 



None of the specimens viewed as young ones exhibit upon the surface lines 

 of growth, except the sternal one, No. 12, in which they are feebly marked. 

 A distal fragment of several posterior costal plates of specimen No. 11, in the 

 immature appearance of its border, clearly proves its youthfulness. 



Besides the thirteen characteristic specimens of E. wyomingensis which 

 have been described or mentioned, fragments of many others are contained 

 in the collections I have had the opportunity of examining. From their com- 

 parative frequency, this appears to have been the most abundant of the fresh- 

 water turtles of the Bridger Tertiary epoch. 



14. Since writing the foregoing, I have had the opportunity of examining 

 another specimen of Emys wyomingensis in- the possession of Dr. Hiram 

 Corson, which was sent to him from Fort Bridger by his son, Dr. Joseph K. 

 Corson. The specimen consists of a nearly complete shell except the posterior 

 fourth of the carapace. It is a little smaller than the fourth -described speci- 

 men, represented in Plate X, and is crushed and distorted nearly in a similar 

 manner. 



The most striking peculiarities of this, which may be distinguished as the 

 fourteenth specimen, are the unusual depth and width of the scutal grooves 

 of the carapace and the proportionate shortness and breadth of the costal 

 scute areas. ~~ w 



The intermediate vertebral plates to the first and fifth are absolutely longer 

 and narrower than in the rather larger fourth-described specimen. The costal 

 plates are shorter, and the second to the fourth, inclusive, are broader. The 



