Apr. 1903. North American Plesiosaurs — Willis ton. 21 



bv a somewhat zigzag line to reach the inner border of the quadrate a 

 little above the border of the pterygoid process. On the inner side, 

 the sutural line passes nearly directly across, and then upward to the 

 inner border. 



The connection with the parietal is definite. The suture indi- 

 cated by Copt- in his figure of Cimoliasanriis snowii (1. c. ) does not 

 exist in the specimen figured, nor is there any such in the skull of 

 Dolichorhynchops osborni here described. In order to definitely deter- 

 mine this fact I removed the portion supposed by Cope to be the 

 supramastoid from the skull of the Cimoliasanriis specimen and carefully 

 cleaned it. thereby proving beyond peradventure that the supposed 

 suture is in reality a fracture. The squamosal, or as it should be 

 called, the squamoso-prosquamosal, in that form, as will be described 

 hereinafter, reaches to the top of the skull, notwithstanding Baur's 

 opinion to the contrary. . The two squamosals touch each other, or 

 nearly do so, as in the skull of Cryptoclidus described by Andrews. 



The temporal bar in the plesiosaurs, it is thus seen, is composed 

 of the jugal, qnadratojugal, squamosal and prosquamosal (supratem- 

 poral). This last element is not distinct in either of the skulls here 

 described, nor is it usually apparent in the adult skull, but Owen* 

 d< scribes and figures it as distinct; Andrews also saysf that " In sev- 

 eral Plesiosaurian skulls in the British Museum the suture between 

 these elements is distinct." 



The quadrate is a short and broad bone, united by a pit-like 

 sutural surface on the inner side with the posterior prolongation of 

 the pterygoid, on the outer side with the squamosal and qnadrato- 

 jugal, as already described. Posteriorly the sutural surface for the 

 squamosal begins a little above the pterygoid articulation, runs down- 

 ward and outward for a short distance, then upward and outward to 

 another point, whence it goes downward to appear on the outer sur- 

 face a little below the angle of the bone, which it follows nearly to 

 the lower articulation. The articulation for the paroccipital is imme- 

 diately above and before the pit for the articulation of the pterygoid. 

 A separated quadrate of another species (7\ anonym 11m), already 

 described in part, with its sutures distinct and the bone undistorted, 

 shows an elongated articular surface, broadest upon the inner end, 

 narrowed and turned upward at the outer extremity nearly to the 

 lower end of the squamosal articulation. A non-articular groove on 

 the inner side of the middle behind divides the articular surface; it 

 does not appear to be present in either of the other species. The 



♦Trans. Geol. Soc. 121, v. Fl. xiv (1840). 

 fQuart. Journ. Geol, Soc. Hi, 250, 1S96. 



