118 University of Kansas Geological Survey. 



terior end terminating to divergent points, as in Clidastes. The 

 anterior lateral wings do not extend as far outward, and the 

 lateral margins, especially toward the front, are thinner and 

 more projecting than in either of the other forms. The pineal 

 foramen is rather small, and is usually wholly inclosed in the 

 parietal, though it may border the anterior suture. 



Supraoccipital. 



Platecarpus. The supraoccipital is a little longer than wide, 

 with a ridge upon the upper surface, terminating in a sutural 

 surface for union with a median tooth or tongue-like projection 

 of the parietal bone. In the region of the semicircular canals 

 the brain cavity is narrowed by a swollen projection on either 

 side, into which is continued, from the exoccipital, a small, 

 round canal. Anteriorly the sutural surface for union with the 

 petrosal continues as a straight, flat surface, inclosing, between 

 the two, a broad cavity for the cerebrum. The upper border, 

 meeting at an angle a little greater than a right angle with that 

 of the petrosal, is a little shorter, and has a deep longitudinal 

 groove, with the margins thin ; the thin posterior margins of 

 the descending wings of the parietal fit into these grooves. The 

 bone articulates with the exoccipital, petrosal, and parietal, 

 with the latter directly, in the middle, by the intervention of 

 connective tissue on the descending part. It forms the superior 

 margin of the foramen magnum, and extends outward, as a 

 broad, flattened squama, for about an inch on the upper side 

 of the base of the exoccipital. 



Basisplienoid. 



Clidastes. The basisplienoid, longer than broad, as seen from 

 below, has the margins deeply concave, the ends nearly trans- 

 verse. In front are three processes, the middle small and short, 

 ending abruptly and transversely; two lateral ones truncate, 

 flattened oval, and obliquely placed to the long axis of the 

 bone. The former is the presphenoid, and has near its base on 

 either side above a small, rounded surface, for cartilage, pre- 

 cisely as in Varanus. I have never seen the presphenoid bone 

 in this genus, but in Platecarpus one similar to that of Varanus 



