632 GEOLOGICAL SURVEY OF THE TERRITORIES. 



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 supercilliary 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 axis of the cranium; the use of this projec- 

 tion is obscure. There is an exoccipital foramen, and a large one in the 

 posterior part of the frontal opposite the postfrontal elevation. 



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

 with broad alte 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 hypopophysis. The neural canal is large, and the neura- 

 pophyses are attached by sutures. The cup is nearly round, very 

 slightly transverse, and vertical. 



This genus differs from Glyptosaunis^ Marsh, in the total lack of cranial 

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



Naocephalus poekectus, Cope. 



Loc. (At., p. 465. 



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

 which are finely rugose. 



Measurements. 



Width cranium at postfrontals 072 



Width parietal behind 012 



Depth postfrontals 018 



Depth prespheuoid anteriorly 014 



Diameter dorsal vertebra, (cup) 007 



From the Bad Lands of Cottonwood Creek. 

 ■ SANIVA, Leidy. 



Geolog. Survey, Wyoming, 1870, p. 368. 



Saniva ensidens, Leidy. 



Loc. cit. 



Vertebrfe, &c., from Black's Fork. The characters agree with those of 

 Iguanavus, Marsh, except in the greater dei)ression of the vertebral 

 centra. 



THIEOSAUKDS, Marsh. 



American Jouru. Sci. and Arts, October, 1872. 



Thinosaurus leptodus. Marsh. 



A considerabie number of remains from Mammoth Buttes (Bitter 

 Creek) agree nearly with Marsh's description, 1. c. 



OPHIDIA. 



Protagras lacustris. Cope. 



Proceed. Amer. Philos. Soc, 1872, p. 471, August 7. 

 A serpent of about the size of the existing pine snake, {FityopMs 

 mclanole7icus,) and allied to the water-snakes of Tro^idonotus and allied 

 genera. 



