GILMORE: the fossil turtles of the UINTA FORMATION 



147 



posterior to this drop on the visceral surface tliere is a sharp median ridge on the 

 midline which measures longitudinally 65 mm. The free borders of the anterior 

 lobe are bevelled off from the superior surface to a sharp edge, which becomes 

 obtusely rounded at the base of the lip. 



Fig. 19. Hadrianus robustus. Anterior half of the plastron. Tyjje, C. M. No. 3342. One-sixth na- 

 tural size. 



The entoplastron is pointed in front and wide behind. It is 134 mm. long, 

 and 147 mm. wide. The gular scutes overlap the anterior end. 



In front of the axillary notch the plastron has a thickness of 29 mm.; im- 

 mediately posterior to the entoplastron of 16 mm.; and at the junction of the 

 hyo-hypoplastron at the center, of 15 mm. This latter measurement in the type 

 of Hadrianus tumidus Hay is only 9 mm. The gular scutes have their greatest 

 extent of 114 mm. antero-posteriorly. Within the area of the gular scutes the 

 surface of the lip is swollen out somewhat below the level of the epiplastral areas 

 bordering it. The superior surface of the lip anteriorly is broadly convex, but 

 flattens toward the posterior end. 



The humerals meet on the midline for 105 mm.; the pectorals for 40 mm.; the 

 abdominals for at least 205 mm. The sulci are broad and deeply impressed. The 

 humero-pectoral sulcus begins just in front of the axillary notch and extends inward 

 and backward for a short distance, then curves forward to the entoplastron, again 

 turning backward to the midline, skirting, but not crossing, the entoplastron. 



The pectoral scutes have quite a different shape from any of the described 

 species of the genus. They are narrow (28 mm.) mesiad of the axillary notch 



