NO. itKJG. OSTEOLOGY OF CAMFT08AVRUS—GILMORE. 213 



It is a thin, siibtriangular plate of bone which meets the jugal an- 

 teriorly by a curved but nearly vertical suture. The greater portion 

 of this bone overlaps the median external surface of the quadrate. 

 It is entirely excluded from the boundary of the infratemporal fossa 

 by an ascending branch of the jugal. 



Jugal. — The jugal is rather a wide bar posteriorly and is con- 

 nected above Avith the descending process of the post frontal and by an 

 ascending process posteriorly with the quadratojugal and quadrate. 

 It is not certainly known that this process reached the descending 

 process of the squamosal as indicated in the restored skull*. A 

 curved, forwardly directed continuation of the jugal completes the 

 lower boundary of the orbital opening, and undoubtedly articulates 

 with the lachrymal, although this point could not be determined from 

 actual observation. The above description is of the left jugal of 

 No. 1887, Yale Museum. 



Nasals. — The nasals are very large, subtriangular bones, which 

 form a considerable part of the upper surface of the skull. They 

 unite posteriorly with the frontals and ]3refrontals and laterally with 

 the iDosterior process of the premaxillse, and slightly with the pre- 

 frontal. Their concave anterior ends form most of the posterior 

 boundary of the external nares. They terminate anteriorly on the 

 median line as two points which meet the superior and posteriorly 

 directed processes of the premaxillse. In skull No. 1887, Yale 

 Museum (see Plate 7), the suture separating the nasals is distinctly 

 shown anteriorly. 



Lachrymals. — The lachrymals are thin plates of bone w^edged in 

 between the maxilla, premaxilla, jugal, and prefrontal. The}^ may 

 have been slightly overlapped by the supraorbitals. Thej^ form part 

 of the anterior boundary of the orbits. These bones were found 

 in situ in specimen No. 1887, Yale University Museum (see Plate 7, I.). 



Sufraorhital. — The supraorbital has an expanded proximal articu- 

 lar end. Posteriorly it tapers rapidly to a small, nearly round ex- 

 tremity which remains free as in Iguana. The proximal end is 

 roughened and deeply cleft, forming two surfaces which meet in the 

 middle at an obtuse angle. When in position these faces are opposed 

 to the lateral surfaces of the prefrontal and lachrymal ( ?), as shown 

 in Plate 7. It forms the external boundary of the supraorbital fossa, 

 as in Iguanodon hernissttrtensls. There is no indication of a posterior 

 supraorbital in C amptosaurus as found in Iguanodon. In No. 1880, 

 Yale Museum, the widest part of the supraorbital fossa was 14 mm. 

 between the posterior end of the supraorbital and the exterior border 

 of the frontal. Marsh's drawing of this region of the skull appears 

 to be erroneous, as will be noticed by an examination of the recon- 

 structed skull of G anbptosavms medius, in the Sixteenth Annual 

 Report of the U. S. Geological Survey, Part II, Plate 53, figs. 1 and^, 

 the fossa being too large, and incorrectly designated as orbit. 



