GILMORE: the fossil turtles of the UINTA FORMATION 



119 



are traceable, and these show them to be narrow at the midhne (18 mm.), but 

 expanding toward their outer extremities where the width is 112 mm. The an- 

 terior lobe is elongated antero-posteriorly, and turns upward with a well-defined 

 sweep toward the carapace, as shown in Fig. 7. Its greatest length is 137 mm.; 

 its greatest width 170 mm. at the base; at a point half-way to the tip measuring 

 117 mm. in width. The sides of this lobe gradually converge from the base to 

 near the anterior end, which rounds in with a shallow but broad median emargina- 

 tion on the anterior end. The posterior lobe is largely missing, though enough of 

 the base remains to show that it had a width of 160 mm. The width of the bridge 

 is 190 mm. 



Fig. 7. Baena giganlca, lateral view of the carapace and plastron, C. M. No. 3-441. Type specimen, 

 one-fifth natural size. 



The sulci defining the intergular scutes cannot be traced. The intergulars 

 meet on the midline for a distance of 29 mm.; the humerals 112 mm.; the pectorals 

 97 mm.; the abdominals 55 mm. The number of inframarginals on the bridge 

 cannot be determined in this specimen. 



This species may be distinguished from all others of the genus by its larger size, 

 the great length of the nuchal scute, and differences in the relative dimensions of 

 the vertebral scutes. The contour of the anterior lobe of the plastron, its greater 

 relative length, and especially its decided upward curvature are all features which 

 serve to distinguish this species. In the presence of five costal scutes the type of 

 this species agrees with several species of the genus, especially Baena riparia and 

 B. hatcheri, but it differs from those forms by the decidedly longer nuchal scute and 

 in the apparent absence of marginal scutella. In the greater length of the third 

 vertebral this specimen is like B. emilice from the same formation, but the greater 

 relative widths of all of the vertebrals and especially the shortness of the fourth, 

 together with other differences to be observed in the plastron, at once distinguish 

 it from that species. 



