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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 84 



The present specimen, therefore, appears worthy of the detailed 

 description that follows: 



Parietal. — The coalesced parietals are much constricted between 

 the supratemporal fossae, the posterior half presenting a tliin median 

 crest that rises to the level of the superior squamosal border. The 

 anterior half is rounded transversely and widely expanded at the 

 end, where it is in sutural contact with the whole posterior ends of 



the frontals and appears to meet the post- 

 frontal on its outer anterior angle. At the 

 center a broad rounded median prolonga- 

 tion is interposed between the frontal bones, 

 as in Lambeosaurus. Posteriorly the slightly 

 widened end of the parietal overhangs the 

 supraoccipital and is suturally joined to the 

 squamosals on either side. This end is 

 visible from a posterior view, as in Cheneo- 

 saurus (see fig. 30). Ventrally the parietal 

 sits astride the supraoccipital with which 

 it is closely joined on the two sides (see fig. 

 29); anterior to the supraorbital it unites 

 ventrally with the alisphenoid, but nowhere 

 is it in contact with the prootic or the exoc- 

 cipital, although Lambe was of the opinion 

 that both of these bones articulated with the 

 parietal in Edmon tosaurus. He was certainly 

 wrong in regard to the exoccipital, for I do 

 not know of any dinosaurian skull in which these two bones are in 

 contact. 



Exoc— 



Figure 29.— Parietal (lacking posterior 

 end) and supraoccipital (U.S.N.M. 

 no. 11893), posterior view. Exoc, 

 sutural border for the e.xoccipital; 

 Ft, sutural border for the frontal; 

 Pa, parietal; Soc, supraoccipital; 

 Sg, articular surface for squamosal 

 articulation. One-half natural size. 



MEASUREMENTS OF PARIETAL 



Greatest length along midline 71 mm 



Greatest width across anterior end 66 mm 



Greatest width across posterior end 15 mm 



Sujjra occipital. — The supraoccipital was found articulated with 

 the overlying parietal, as shown in figure 29. Viewed posterioily the 

 supraoccipital is a subtriangular, blocklike bone that is enclosed above 

 by the parietals and squamosals and that is in contact below wdth the 

 exoccipitals. The broad, rounded, bilobed upper surface of the 

 median crest of this bone is smooth and gives no indication of sutural 

 union with the overlying parietal. It was evidently a cartilaginous 

 union such as is commonly found in the Sauria. A similar condition 

 exists in Camytosaurus and Stegosaurus. In aged individuals this 

 surface may become coossified with the parietal, as is known to be the 

 case in Stegosaurus. On either side well below the crest these two 



