20 Field Columbian Museum —Geology, Vol. II. 



from the quadrate is situated as in Cinwliasaunts snowii, at the external 

 angle of the quadrate, which it borders to its upper extremity.. At 

 the lower extremity there is a very distinct squamate suture, running 

 upward and forward and becoming lost about twenty millimeters from 

 its origin. This suture is clearly apparent on the two sides, and is 

 also seen in the skull of Cifnoliasaurus snowii, as it was figured by 

 myself (1. c.) and Cope*. Just what the course of the suture is 

 anteriorly I cannot say, but I believe that it is indicated by a line 

 passing forward to the maxilla, and excluding that bone from union 

 with the squamosal. Whatever be its relations anteriorly, I doubt 

 not that the quadratojugal exists as a distinct ossification in the 

 plesiosaurs. In a separated quadrate of another species of plesiosaur 

 ( T. aiwnymum Will.), from the Benton of Kansas, the sutural sur- 

 faces for union with the quadratojugal and squamosal are clearly dis- 

 tinguished. The quadratojugal does not enter into the formation of 

 the condylar surface of the quadrate, as has been suspected, and as it 

 does in Sphenodon; this is certain. On the outer side of this quadrate, 

 just above the articular surface, there are two sutural surfaces — one 

 on the posterior and outer border, for the attachment of the squamosal, 

 the other on the anterior border for the attachment of the quadrato- 

 jugal, which, in this case, as also in Dolichorhynthops osbomi, must 

 have been overlapped in part by the squamosal. In Cimoliasaurus 

 snowiii the suture between the squamosal and the quadratojugal is 

 very clearly indicated from the exterior, the squamosal not descend- 

 ing as low as in the other species. The suture shown as separating 

 the quadratojugal from the squamosal anteriorly is conjectural, but I 

 believe, as already stated, that it will be found to extend as far for- 

 ward as the maxilla. 



The suture separating the squamosal from the postorbital is short 

 and vertical, joining the border near the anterior extremity of the 

 bone, as seen from the outer side. The suture joining the jugal is a 

 squamous one, extending on the inner side nearly to -the margin of the 

 orbit, but leaving a small space for the union of the ectopterygoid 

 with the jugal. The suture with the maxilla is long and oblique, con- 

 cealed. in about half its extent by the jugal. I believe, however, that 

 the squamosal is really separated from the maxilla by the intervention 

 of the quadratojugal, as already described, and for which there seems 

 to be some evidence in the specimen. On the right side the maxilla 

 had been removed by maceration, leaving the sutural surface for the 

 temporal element very clear in its whole extent. 



Posteriorly, the sutural line of the squamosal passes downward 



* Froc. Amer. Phil.Soc. 1894. 



