GEOLOGICAL SURVEY OF THE TERRITORIES. 631 



and arched above the limbs. The carai^ace in qnite convex. The plas- 

 tron has the posterior lobe emargiuate rather than bifnreate, as seen in 

 H. Gorsonii. 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 luesosternal bone is 

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



The anterior margin of the carapace is somewhat flared above the 

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

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

 margin. 



Measurements. 



M. 



Length, (below) 730 



Wkltb at middle 437 



Width at hind limbs 525 



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

 is, perhaps, thelargestof our extinct land-tortoises, and is founded on a 

 beautifully perfect specimen from the bluff's of Cottonwood CJreek. 



Hadrianus Corsonii, Leidy. 



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

 Philos. Soc, 1872, 463 ; Hadrianus qiiadralus, 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 iii front, which is turned outward, forming a 

 strong angle with the plane of the upturned front of tlie 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 i)ostabdominal projecting as a triangle. There is a 

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

 greatly 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 exjjanded and truncate anterior outline, which is nearly straight 

 between two lateral obtuse angles. 



Length carapace, M. .750=29 inches; width, .030. The marginal scuta 

 are narrow, and there is a large nuchal x^late. 



Abundant in the Bridger beds. 



L ACERTILIA. 

 NAOCEPHALUS, Cope. 



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



Established on an incomplete cranium, with vertebra^, 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 transverse ; its outline is rectangular, so as al- 

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

 the parietal, leaving but a narrow exposure of the i)Osterior 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, 



