[lambe] crest of the HORNED DINOSAUR^CENTROSAURUS 9 



necessary. In either case the fontanelle, lying on the inner side of tlie 

 squamosal and the attenuated lateral c xtcnsion of the posterior ] art of 

 the parietal, must have been of considerable size, probably much larger 

 than the fontanelles of the crest of Ccnirosaurus apertus. The undula- 

 tions of the outer border of the squamosal are continued in that of the 

 free part of the parietal (figures 4 — 7). The dotted outlines in figures 

 4 and 6 indicate the position of the parietal extension, when applied 

 to the squamosal, and as it was found in the rock. The figures 7a, 7b 

 and 7c give the outlines of transverse sections of the bone at the points 

 indicated. 



It is seen then that in Monoclonius canadensis the posterior crest 

 extended far backward, that it was made up of the parietals (probably 

 coalesced so as to have somewhat the form of the corresponding portion 

 of the frill of Monoclonius belli) and the squamosals, the latter entering 

 largely into the composition of the sides of the crest, and that fontanelles 

 of very large size were present. We know also that the fontanelles were 

 not included entirely within the parietals, as in Centrosaurus, but werei 

 bounded laterally in front by the squamosalsi. 



Measurements of squamosal, etc. 



Length on curve of outer border ''570 



Length on curve of inner border , "573 



Length from posterior end to centre of front margin "SSS 



Breadth across front margin '355 



Thickness near outer border, at mid-length "028 



Thickness near inner border, at mid-length '038 



Length of fragment of parietal extension "SOS 



Breadth of same at mid-length "064 



Greatest thickness of same at mid-length -030 



