GEOLOGICAL SURVEY OF THE TERRITOEIES. 631 



and arched above the limbs. The carapace in quite convex. The plas- 

 tron has the posterior lobe emarginate rather than bifurcate, as seen in 

 H. Corsonii. Each projection represents a right-angled triangle rather 

 than a wedge. The anterior lobe presents an elongate lip, which is ex- 

 panded, and slightly emarginate at the end. The mesosternal bone is 

 heart-shaped, the posterior emargination being wide and deep. 



The anterior margin of the carapace is somewhat flared above the 

 limbs. The nuchal scutum is very narrow transversely, but elongate. 

 The carapace descends and is incurved in the middle of the posterior 

 margin. 



Measurements. 



M. 



Length, (below) 730 



Width at middle 4'37 



Width at hind limbs 525 



This species differs from the if. Corsonii in many important points. It 

 is, perhaps, the largest of our extinct land-tortoises, and is founded on a 

 beautifully perfect specimen from the bluifs of Cottonwood Creek. 



^ HADEiANtTs Corsonii, Leidy. 



Geological Survey, Montana, 1871, p. 366 ; Testudo liadrianus, Cope. Proceed. Am. 

 Philos. Soc, 1872, 463 ; Radnamis quadratus, loc. cit., 468. 



Indicated by many individuals, two nearly perfect, another chiefly 

 represented by a complete plastron. This proves the existence of a 

 very massive species of the terrestrial genus Testudo. The plastron 

 presents a short wide lip in front, which is turned outward, 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 higher ridge. The posterior lobe is deeply 

 bifurcate, each postabdominal projecting as a triangle. There is a 

 notch at the outer angle of the femoral scute. The hyposternal bone is 

 gTeatly thickened within the margin above, and an elevated ridge bounds 

 the basin of the plastron behind, as before. The middle.of the plastron 

 is thin. 



The carapace is without marked keel or serrations. It is remarkable 

 for its exi)anded and truncate anterior outline, which is nearly straight 

 between two lateral obtuse angles. 



Length carapace, M. .750=29 inches; widtl;, .630. The marginal scuta 

 are narrow, and there is a large nuchal plate. 



Abundant in the Bridger beds. 



LACEETILIA. 

 ijfAOCEPHALUS, Cope. 



Proceed. Amer. Philos. Soc, 1872, p. 465, (July 29.") 



Established on an incomplete cranium, with vertebrae found associated. 

 No teeth are preserved, nor any part of the mandible. The remaining 

 portions of the cranium are, however, highly characteristic. 



The occipital descends posteriorly, and bears a pair of lateral ridges, 

 which converge rapidly posteriorly. This bone is united with the parie- 

 tal by suture, which is transversse ; its outline is rectangular, so as al- 

 most to reach the frontals, which are prolonged backward on each side 

 the parietal, leaving but a narrow exj)osure of the posterior processes of 

 the parietal. These extend backward, and are broken off in the speci- 

 men, but they probably formed parts of arches. The parietal is single, 



