A NEW EXTINCT TURTLE FROM IDAHO — GILMORE 



parison. The limb and foot bones do not display any distinguishing 

 characteristics except that they are more robust in their proportions 

 than in extant species of Pseudemys of corresponding size. The 

 unguals of the articulated hind foot are elongate, with sharp tips, 

 indicating that the type specimen may be a male. 



Remarks. — Although in skull struc- 

 ture the tj'^pe has its closest resem- 

 blances with P. rubriventris, the palatal 

 surfaces of the jaws are so unlike that 

 when considered in conjunction with 

 differences found in the shells the ques- 

 tion of their generic identity is raised. 

 The alveolar surface of the mandible 

 is much more like that of Grapiemys 

 pulchra, but the pointed skull and lack 

 of palatal ridges at once distinguish 

 this form from the extinct species. I 

 call attention to these differences in 

 the palate for the reason that both 

 paleontologists and herpetologists 

 have made much use of these characters in the classification of 

 the turtles, but an examination of a considerable series of recent 

 skulls shows that there is much variation in the palatal structure 

 and that they can not therefore always be relied upon to furnish 

 hard and fast diagnostic characters. The present species can hardly 

 belong to Giapiemys or Trachemys as defined by Hay, and for the 

 present I shall refer it to the genus Pseudemys, although the specimen 

 is not entirely in accord with that genus as we understand it to-day. 

 If correct in this assignment it is the most ancient occurrence of 

 Pseudemys yet recorded. 



Figure 5.— Hyoid of Pseudemys idahoensis, 

 U. S. N. M. No. 12059. Type. Superiofl- 

 view. Natural size 



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