NO. 1666. OSTEOLOGY OF CAMPT08AURU8—0ILM0RE. 211 



all other sutures are distinctly seen, failed to show any indication of 

 an interparietal suture. Hulke " has observed that Hypsilophodon 

 foxii, Iguanodon nuintelU^ and C atnptosaurus {Iguanodon) prest- 

 wichil all have unpaired parietals. 



Seen from above the parietals are comparatively short, heavy 

 bones. Their lateral surfaces, which form the upper walls of the 

 brain case, are smooth, concave antero-posteriorly and thus constricted 

 medially into a rounded crest, and without the sharp median sagittal 

 ridge found in Iguanodon. Anteriorly the expanded end unites with 

 the broad plate-like frontals by an angular suture. Laterally a pro- 

 longation of the anterior portion of the parietal curves outward to 

 meet the postfrontals, and with these bones form the upper anterior 

 boundary of the supratemporal fossa. Similarly the postero-lateral 

 border turns outward, joining the squamosal with which it bounds 

 posteriorly the upper opening of the fossa. Ventrally it encloses the 

 upper portion of the supraoccipital. In the skull of G. medius, No. 

 1880, Yale Museum, the parietal has a transverse width of 51 mm. at 

 its middle. There is no parietal (pineal) foramen in Camptosaurus: 



Squamosal. — The following description of the squamosal of Camp- 

 tosaurits, found among Professor Marsh's unpublished notes, is 

 based on the left element of C. niedius, No. 1880, Yale Museum. 



The squamosal fits very snugly on the head of the quadrate, and probably 

 excludes the quadrate entirely from touching the paraoccipital process as in 

 Splicnodon. In position it is most nearly related to that of Iguana. It has four 

 distinct processes. The postfrontal process is very thin, flat, and arched out- 

 ward above. The sutural surface is rather more than 11 inches in length, 

 reaching to within a half inch of the tip of the quadrate. The head of the 

 quadrate fits closely into a pit on the under surface. A slender process runs 

 downward along the anterior exterior border of the quadrate containing the 

 articulation for a third of the entire length. This corresponds in position to 

 the same process on Sphenodon that runs down to articulate with the quadra- 

 tojugal. In the present case it is much more slender and probably does not 

 reach that bone. 



The parietal process extends inward along the dorsal border of the 

 paraoccipital process to meet the outward-turned process of the parie- 

 tal, the two forming the upper posterior border of the supratemporal 

 fossa as in Stegosaurus. 



Frontals. — Viewed from above the paired frontals are irregularly 

 five-sided bones, longer than wide, with a flattened, smooth dorsal 

 surface. Posteriorly they unite with the parietal and postfrontals, 

 and externally with the post- and prefrontals. The postfrontal bor- 

 der is convex instead of concave and extends anteriorly much farther 

 than as first indicated by Marsh. The prefrontal border extends 

 diagonally from the external border to the middle of the anterior 

 end. A short, smooth surface between the anterior and posterior 



«Phil. Trans. Royal Soc. London, CLXXIII, 18S2, p. 1037. 



