6 



Length marginal Oil 



Width " 016 



The three specimens are from the bluffs of Cottonwood Creek, "Wy- 

 oming. 



Naocbphalus porrecttjs. Cope. 



Gen. et sp. nov. Lacertiliarum. 

 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. 



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

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

 etal by suture, which is transverse ; its outline is rectangular, so as 

 almost to reach the frontals, which are prolonged backwards on each side 

 the parietal, leaving but a narrrow exposure 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, 

 and there is no parietal fontanelle. The bone is triangular in outline 

 with the apex anterior, dividing the frontals. These are contracted at 

 the orbits, and have a projecting superciliary head ; anteriorly they are 

 thickened. The postfrontals are of remarkable form. They are mas- 

 sive, and compressed from before backward ; they rise considerably 

 above the level of the front, and bear on their summits a cotyloid cavity, 

 which is transverse to the exis of the cranium ; the use of this projection 

 is obscure. There is an exoccipal foramen, and a large one in the poste- 

 rior part of the frontal opposite the postfrontal elevation. 



The sphenoid is a compressed keel-shaped bone, round below, and 

 with broad alse along much of its length. The occipital condyle is sub- 

 condate depressed in outline, with a vertical obtuse angle in the middle 

 and the sides somewhat plane. 



A dorsal vertebra preserved has a single vertical capitular process, and 

 a short hypapophysis. The neural canal is large, and the neurapophyses 

 are attached by sutures. The cup is nearly round, very slightly trans- 

 verse, and vertical. 



The cranium is smooth above, except the anterior part of the frontals, 

 which are finely rugose. 



This genius is more or less allied to the Theeoplossa, but better material 

 will be requisite to decide the question of affinities fully. 

 Found with the preceding specimens. 



M. 



Width cranium at postfrontals 072 



" parietal behind 012 



Depth postfrontal 018 



" pre-sphenoid anteriorly .. . .014 



Diameter dorsal vertebra (cup) 007 



This genius differs from Qlyptosourus, Marsh, in the total lack of cra- 

 nial shields, and from tiauiva, Leidy, in the nearly round vertebral centra. 

 July 29, 1872. 



