Williston.] Mosasaurs. 127 



is much more concave in C. tortor. The inferior surface appears 

 to be broader from side to side in C. tortor. 



Quadrate No. 1119 ( pi. lxiv, f . 4) is in a measure intermediate 

 between that of C. tortor and C. velox. The internal posterior 

 rugosity is smaller, the anterior border above more concave, 

 and the anterior surface somewhat channeled. The quadrate 

 of C. westii closely resembles that.of C. tortor. 



The quadrate of Mosasaurus horridus agrees best with that 

 of C. tortor, though very different. The interior border from 

 above downward is slightly convex in the middle, projecting 

 beyond the plane of .the ends, instead of being concave. The 

 infrastapedial rugosity is very much larger than in C. tortor, 

 and situated higher up. Between it and the anterior border 

 there is a strong channel, terminating near the thin infe- 

 rior border of the stapedial pit. The ridge limiting the infe- 

 rior border of the ear cavity posteriorly is sharper, though less 

 prominent. The suprastapedial process is much shorter, ter- 

 minating almost exactly opposite the middle of the bone. It is 

 much broadened below from side to side. The superior inner 

 process of the articular surface is very short and obtuse, with 

 only a short concavity between it and the alar process. The 

 anterior surface is nearly straight from side to side in the mid- 

 dle and only moderately convex longitudinally. The stapedial 

 pit is of large size, oval and vertial, its upper end reaching 

 only a little above the upper end of the meatal notch. The in- 

 ferior articular surface is much elongated from side to side and 

 only a little broader on the outer part. In Clidastes its breadth 

 is much greater on the outer part. 



The quadrate of Brachysaurus (pi. xlvi, f. 2) is, in several 

 respects, very remarkable. Its inner side from above down- 

 ward is very deeply concave, the border sinuous. The border to 

 above the middle'is thin and sharp, the face including a deep 

 channel that terminates on the anterior side of the meatus. 

 On the upper part, as the deep channel turns backward to the 

 opening, the border is broader, but limited posteriorly by a 

 rather sharp edge that runs to the inferior part of the stapedial 



