Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 21 
by 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 Cope in his figure of Crmoliasaurus 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 Crmolzasaurus 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 Crvpftoclidus described by Andrews. 
_ The temporal bar in the plesiosaurs, it is thus seen, is composed 
of the jugal, quadratojugal, 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* 
describes and figures it as distinct; Andrews also sayst that ‘‘ In sev- 
eral Plesiosaurian skulls in the British Museum the suture between 
these elements 1s distinct.” 
The guwadrate 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 quadrato-— 
jugal, as already described. Posteriorly the sutural surface for the 
squamosal begins a little above the pterygoid articulation, runs down- 
ward and outward fora 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. anonymum), 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. Avenon-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. (2), v, Pl. xiv (1840). 
tT Quart. Journ. Geol. Soc, Jii, 250, 1896. 
