A NEW EXTINCT TURTLE FROM IDAHO — GILMORE 



The sulci outlining the scutes of the carapace are shallow but plainly 

 impressed. Those between the marginal and costal scutes run along 

 on the peripheral bones a short distance below the costo-peripheral 

 sutures except in front and back, where they deviate outward farther 

 away from the sutures. Posteriorly the sulcus crosses the midline on 

 the anterior end of the pygal, as in Trachemys hilli. The form of the 

 scutes is plainly indicated in Figure 1. 



Skull. — The skull and articulated lower jaws were found in the 

 matrix witliin the carapace. (Figs. 3, 4.) They are uncrushed and 

 in beautiful preservation. Seen from above, the outline of the skull 

 expands from the squamosal processes forward to the front of the 

 quadrates. From the posterior ends of the maxillae it converges 

 to the snout, which is 

 squarely truncate. The 

 interorbital space is mod- 

 erately wide and flat; 

 posteriorly the upper 

 surface is dished. The 

 length of the skull from 

 the snout to the occipital 

 condyle is 57 mm, to 

 the tip of the crest 70 

 mm, the width over the 

 auditory chambers 50 

 mm. The interorbital 

 space is 14 mm wide, 

 the zygomatic arch 11 

 mm. The orbits are 

 subcircular in outline 

 and look forward and 

 outward; the antero-posterior diameter is 14 mm, the vertical diam- 

 eter 12 mm. The nasal opening is 9 mm wide, suboval in outline 

 with the greatest diameter transverse. Choana between the eyes. 

 Alveolar surfaces broad. Width of jaw at symphysis slightly less 

 than horizontal diameter of the orbit. 



Little is known of the skull in the extinct Emydidae. In a study 

 of all North American materials of this family, Hay ^ found only a 

 single emydid skull, which he provisionally referred to Echmatemys 

 sp. The present specimen therefore can not be contrasted with 

 extinct members of this family. 



In comparing the skull under consideration with available skulls of 

 recent turtles in the National Museum collection, I find the closest 



Figure 3.— Skull of Pseudemys idahoensis, U.S.N.M. No. 12059. 

 Viewed from the left side. Type, ang, Angular; art, articular; 

 CO, coranoid process; d, dentary; /r, frontal; jtt, jugal; mx, maxil- 

 lary; pa, parietal; pf, postfrontal; prf, prefrontal; gj, quadrato- 

 iugal; qu, quadrate; sg, squamosal; sup, supraoccipital; sur, 

 surangular. Natural size 



' Hay, O. P., The fossil turtles of North America. Carnegie Inst. Washington Publ. 75, p. 297, pi. 45, 

 figs. 11-13, 1908. 



