2, PROCEEDINGS OF THE NATIONAL MUSEUM vol.82 



The greatest length of the carapace is 318 mm (284 mm); the 

 greatest width 220 mm (207 mm). The anterior margin is shallowly 

 excavated at the center, the posterior margin strongly scalloped. 

 The pygal region presents an exaggerated peculiarity of structure 

 where it forms an inverted U-shaped notch covering the tail. This 

 peculiarity causes a prominent posterior projection in the pygal 

 region that is clearly discernible in the illustrations. (Pis. 1, 2.) 

 Certain species of the extant Gra'ptemys show a somewhat similar 

 elevation of the pygal, but in none of the available specimens does 

 it reach the extreme development of the fossil. 



Figure 1.— Carapace of Pseudemys ida'ioensis, U.S.N.M. No. 12059 

 Type. One-third natural size. 



The surface of the type carapace is undulating but without sculp- 

 ture, except for faint growth ridgings across the outer ends of the 

 costals. The paratype, however, shows additional sculpturing in 

 the form of faint parallel grooves and ridges that cross the posterior 

 half of the costals at right angles to their sutural borders. Likewise 

 the peripheral surfaces are faintly sculptured. The plastral surfaces 

 are devoid of ornamentation. 



