7 



FOSSIL TURTLES OF NORTH AMERICA. 



nallv a length of about 395 mm., measured in a direct line. The greatest width, 340 mm., is 

 across the middle of the length of the carapace. Across the axillary notches the width is 315 

 mm., and that taken 25 mm. in front of the hinder extremity of the plastron is 306 mm. It will 

 be seen therefore that the extremities of the shell are broad. The height of the shell is now 145 

 mm. bur it was doubtless greater during life. 



Figs. 49 and 50. Bnena arenosa. X}. No. 11 15 A. M. N. H. 



49. Carapace. Shows the scute areas. Front injured. 



50. Plastron. Shows many of the bones and the scute areas. Front restored. 



The hinder border of the carapace (fig. 49) is rather thin and acute, scallopt as in the 

 other species of the genus, and flared somewhat upward. The anterior border is obtuse. All 



the bones are thoroly co-ossified, so that the forms of the neurals 

 can not be determined. The surface is uneven, and especially 

 in the areas occupied by the vertebral scutes there are various 

 longitudinal, transverse, and oblique ridges. A slight depression 

 occupies the midline of vertebrals 3 and 4. The accompanying 

 table gives the dimensions of the vertebral scutes. In general, 

 they are wider than long. 



As is not infrequent in the species of the genus, there are, on 

 the left side at least, 5 costal plates. The most anterior is cut 

 from the front of the one usually called the first; altho the most anterior vertebral is reduced 

 somewhat in width thereby. The portion of the rim of the carapace between the outer border 

 of the small anterior costal scute and the posterior vertebral is occupied by 12 marginal scutes. 

 1 be plastron (fig. 50) has an even, but granulated, surface. The anterior lobe is 133 

 mm. wide at the base. The bridges are 155 mm. wide. The limits of the mesoplastra are 

 indistinctly discernible. They were about 20 mm. wide at the midline and expanded distally 

 to about 90 mm. The hinder lobe is 141 mm. wide at the base and 105 mm. long. It dimin- 

 ishes in width slowly backward and the end is truncated. At the ends of the femoro-anal sulci 

 the width is yet 113 mm. The lobe lacks about 60 mm. of reaching backward to the hinder 

 border of the carapace. 



