STEGOCERAS VALIDUS. 



99 



minute columns of bone arranged perpendicular to and radiating from the external surface of 

 the various bones of the roof of the skull, with which they are firmly coossified at their bases, as 

 shown in fig. 100. 



If my interpretation, which differs only in a few unimportant particulars from that of 

 Nopcsa, is correct, Lambe was not only wrong in considering these elements as prenasals/' 

 but he also possibly mistook the anterior for the posterior extremities. I would interpret the 

 large median cavity shown on the inferior surface in fig. 99 as the upper portion of the brain 

 cavity, while the transverse suture which divides it into ante- 

 rior and posterior moieties I would consider the parieto-frontal d&%%?$ff& 

 suture, rather than the fronto-nasal, as believed by Nopcsa. ( A' '. •.■; \ 



Thus the bone in front of the suture becomes, according ' /% v '^W^lmm, 



to my interpretation, the frontal rather than the nasal, as /. £\-^ 



regarded by Nopcsa, though faint lateral sutures just in advance - M ; j> 1||; ; ||J|I$L 

 of the interorbital constriction may mark the posterior borders i'.'S.Of , ~f/r/t^^ ,-, ^Wi^ 

 of the nasals. Like Nopcsa, I regard the lateral cavities as (_[ fC / 'A , ' v^»»g 

 orbital. Posteriorly in the larger of the two specimens there W*i- . //i 

 are two deep lateral cavities which opened externally by a small | M --M 

 circular foramen, only the internal border of which latter is rep- f ^ -^TAt 

 resented in either specimen. The deep lateral cavities I inter- V :. ! ^ : "?"--^J, ' M?0f : -:''' 

 pret as infratemporal fossa?, while the circular foramina opening /' ':)■ ^."''■'•i ' : V%C> " ,SWr0''' : . I - 

 into them may possibly represent the supratemporal fossae, M~~ ;. ; *> ;., \'-'$y% i-.-m, 

 though from the position of these foramina this interpretation \[~S^ ":. - jM 



appears hardly probable. ^^L^^LL : I 

 On the larger of the two ^*^||pR; 

 ' %fev more complete specimens 



' : '^4i€lMllllf^M^^^^K l'ust behind that cavitv FlG -»- Meri orviewof %o(«ras raKte 



WmltmMlwm>)l ! ■ ^lC~ifi; >) ; 13m i • n t i • 1 Lambe, No. 1423, Geol. Surv. Canada. 



' : ^^^S^W^\M' i: jW Wnicil [ haVe Considered a , Anterior; p, posterior; n, nasal; /, 



the brain Cavity there is a frontal; pe, parietal; so, supraoccipital. 



Natural size. 



broken or sutural surface, 

 fig. ioo.-side view of type specimen, No. 515, followed by a rather deep median excavation terminating 

 Geoi. surv. Canada, showing columnar struc- anteriorly in two shallow pits separated by a median 



ture of dermal ossification. One-half natural septum _ Thig may have formed the roof of the foramen 



magnum. 

 Without more perfect material it is quite impossible to determine definitely either the 

 homologies of these elements or the nature of the animal to which they pertained. In the 

 present writer's opinion, however, there is no good reason for considering them as horn bearing, 

 or the animals to which they belonged as pertaining to the Ceratopsidae. I, therefore, do not 

 include them in that group. 



Principal dimensions of bones of Stegoceras validus. 



For the larger (type specimen No. 515, Geol. Surv. Canada): Mm. 



Greatest length 106 



Greatest breadth 60 



Greatest depth ... 41 



For the smaller (No. 1423, Geol. Surv. Canada) : 



Greatest length _ 64 



Greatest breadth 44 



Greatest depth _• 31 



Taken as a whole the collection of Ceratopsia made by Lambe from the Belly River beds 

 is a most important one, since it furnishes much valuable evidence not only regarding the dis- 

 tinctly generic characters of these earlier and less specialized members of the family, but relating 

 also to the ancestry and phylogeny of the later, more highly specialized, and much better known 



a See footnote c, p. 98. 



