TESTUDI]S^ATA. 141 



The anterior margin of the carapace is somewhat flared above the limbs. 

 The nuchal scutum is very narrow transversely, but elongate. The cara- 

 pace descends steeply and is incurved in the middle of the posterior margin. 

 The superior portions of the anal scuta cover an ovate projection of the 

 surface. 



Measurements. 



Length (below) 730 



Width .at middle 4:17 



Width .at hind limbs 525 



This species is perhaps the largest of our extinct land tortoises, and is 

 founded on a beautifully perfect male specimen from the bluffs of Cotton- 

 wood Creek. 



Hadrianus corsoni Leidy. 



Geological Survey Montana, 1871, p. 365. Tistudo hadriaiius Cope, Proceed. Amer. Philos. Soc, 1872, p. 



463. Sadrianiis qitadratits, loc. cit., p. 468. 



Indicated by several individuals, one nearly perfect, the others rep- 

 resented by all parts of the skeleton. This proves the existence of a very 

 massive species of the terrestrial genus Iladrianus. The plastron presents a 

 short, wide lip in front, which is turned outwards, forming a strong angle 

 with the plane of the upturned front of the lobe. This lobe is bordered by 

 a thickening of the upper surface, which cuts off the basin from the lip, as 

 a high ridge. The posterior lobe is deeply bifurcate, each post-abdomnal 

 projecting as a triangle. There is a notch at the outer angle of the femoral 

 scute. The hyposternal bone is generally thickened within the margin 

 above, and an elevated ridge bounds the basin of the plastron behind, as 

 anteriorly. The middle of the plastron is thin. The carapace is without 

 marked keel or serrations. It is remarkable for its expanded and truncate 

 anterior outline, which is nearly straight between two lateral obtuse angles, 

 thus giving a quadrate outline when viewed from above or below. Length 

 of carapace, "TSO — 20 inches, width ".630. The marginal scuta are nar- 

 row, and there is a large nuchal plate. 



Abundant in the Bridger beds. 



