33 



FOSSIL TURTLES OF NORTH AMERICA. 



The type, No. 5933, measures, from the front of the plastron to the rear, 280 mm. The 



length of the carapace (fig. 4-{2) is 502 mm. 



Dimensions of neurals. 



Dimensions of costal bones. 



The width in a straight line is 225 mm., thus 

 being 74 per cent, of the length. The shell has 

 been little, if any, crusht downward, and the 

 height is now 108 mm. The front is slightly 

 incurved in front. The anterior border is sub- 

 acute, and the anterior peripherals thicken rap- 

 idly. The surface of the shell is smooth. 



The neurals are rather broad, having the 

 dimensions shown in the table herewith. 



The nuchal is 48 mm. long, tf mm. wide 

 at the free border, and 63 mm. where widest. 

 The costal plates behind the first pair are 

 differentiated so that the proximal ends are 

 alternately narrower and wider, while the distal 

 ends are alternately wider and narrower. The dimensions of the costal plates are given in 

 the table above. 



The table below shows the dimensions of the peripherals, the vertebral scutes, and 

 the marginals. 



The height of the third peripheral is only 44 per cent, of the height of the first costal near 

 its hinder border. The width of this costal is 70 per cent, of its height. 



The nuchal has a length of 14 mm. and a width 

 the first, are of moderate width. 



1 5 mm. The vertebral scutes, except 



The anterior lobe of the plastron (fig. 433 ) has a length of 76 mm., and a width of 1 13 mm., 

 at the base. The borders continue straight forward to the suture between the hyoplastron and 

 the epiplastron, then curve toward the lip. The latter is 49 mm. wide, truncated and provided 

 with a short stout tooth on each side. It extends as far in front as the border ot the nuchal. 

 The greatest thickness of the epiplastral bones is 13 mm. The thickening on the upper surface 

 (fig. 434) extends backward 24 mm. The horn-covered surface is 18 mm. wide, becoming 

 reduced to 16 mm. at the hyoepiplastral suture. The entoplastron is 47 mm. long and 53 mm. 

 wide. The anterior buttresses ascend only about one-third the distance from the lower to the 

 upper border of the first costals. 



The bridge has a width of 118 mm. The hypoplastrals, in the midline, just behind the 

 suture with the hyoplastrals, are 13 mm. thick. This is reduced very little toward the anterior 

 and the posterior buttresses. 



The hinder lobe has a length of 90 mm. and a width of 126 mm. The buttresses are 

 broad. The beveled surface (fig. 435) on the upper side of the hinder lobe is of only moderate 

 width, 19 mm. at the suture with the xiphiplastral. The posterior notch appears to have been 

 rather shallow . 



The gular scutes are 40 mm. long; the numerals, 3,7, mm.; the pectorals, 48 mm.; the 

 abdominals, ji, mm.; the femorals, 38 mm.; the xiphiplastrals, at the midline, 45 mm. The 

 axillary scutes are quadrilateral and fail by 15 mm. of extending backward to the fifth marginals. 

 The inguinals lack the same distance of reaching to the sixth marginals. 



No. 5954 is of almost exactly the same size as No. 5933, the length of the plastron to the 

 hypoxiphiplastral suture being 218 mm. It varies in slight degrees from the type. The neurals 



