are faced with enamel, but have only smooth cementum without sculpture. 

 There are no molars, but the inferior face of the maxillary bone is 

 rugose as though alveoli had been absorbed. There are traces of very 

 shallow alveoli. 



The cast of the brain indicates smooth oval hemispheres which leave 

 the cerebellum and olfactory lobes entirely exposed. The latter are ovoid 

 and expanded laterally. 



The cranium is depressed, and has a trace of interparietal crest. The 

 anterior margin of the temporal fossa is marked by a curved angle on 

 each side of the frontal bone. The supra-orbital arch is very short. 



This curious animal reminds me of a small Megalonyx with flattened 

 cranium. The cutting teeth above are, however, more like those of 

 rodents. 



M. 



Length cranium (3.5 in.) 0.090 



Width " (without zygomas) 040 



" " near end of nasals 027 



" upper cutting tooth 007 



Depth " " " 0085 



Length exposed part lower tooth 009 



Width " " " " 006 



Hadkianus octonakia. Cope. 

 Gen. et sp. nov. 

 This is genus of true Testudinidai, designed to include those with 

 double anal scuta, and posterior lobe of the plastron bifurcate . In addi- 

 tion to the species above named, the H. quadratus (Testudo hadriana 

 Cope), and probably the species to which belong a small piece named by 

 Leidy, T. corsoni, pertain to the genus. 



The H. octonarius is distinguished from its congener in many ways. 

 It is of elongate form, strongly contracted at the bridges, but expanded 

 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. quadratus. 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 muchal scutum is very narrow transversely, but elongate. 

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

 margin. M. 



Length (below) 730 



Width at middle 437 



" at hind limbs 525 



This species differs from the H. quadratus in many important points. 

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

 a beautifully perfect specimen from the bluffs of Cottonwood Creek. 

 August M, 1872. 



