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protuberance on the supraoccipital, to which the exoccipital con- 

 tributes an outer portion. This articulation has been more fully 

 described in connection with the supraoccipital. External to this 

 cup the squamosal sends downward and outward a narrow, com- 

 pressed, tapering process. In the articulated skull this process is 

 closely applied posteriori}^, especially at its upper end, to the para- 

 occipital process of the exoccipital, and they contmue in apposition 

 throughout their lengths. 



Ra 



Figure 30.— Articulated squamosal, parietal, and supraoccipital (U.S.N.M. no. 11893). Pa, 

 parietal; qu, cotylus for the quadrate; Po, sutural surface for articulation of postorbital; Soc, 

 supraoccipital; Sq, squamosal. One-half natural size. 



From a lateral aspect the squamosal presents a wide surface between 

 its upper border and the top of the cotylus for the head of the quad- 

 rate. This is a pecuharity distinctive of all known members of the 

 Lambeosaurinae, as the other members of the Hadrosauridae are 

 relatively narrow in this view. The cotylus is deep. A pointed 

 process of moderate length extends downward from its anterior border 

 lapping along the front of the quadrate. Above and anterior to this 

 process the squamosal is a short tapering process that unites by 

 squamous union with the inner side of the postfrontal. The posterior 

 overlap of the postfrontal is Y-shaped with the ventral branch much 

 longer than the upper, as indicated by the sutural surfaces on the 

 exterior surface of the squamosal. This same condition is found in 

 Lambeosaurus, Corythosaurus, and Saurolophus. 



