20 



THE CEKATOPSIA. 



The squamosals vary greatly in form in the different genera and species. In Triceratops 

 flabellatus the form of the squamosal is intermediate between that seen in Ceratops montanus 



Fig. 12.— Superior view oi frill oi Torosaurus gladius (type), No. 1831, Yale Museum. p r Parietal: sq, squamosal; pf, parietal fontanelle 

 sf supratemporal fossa; pfs, surface for contact with postfrontal; x, foramen analogous to the postfrontal foramen in Triceratops. 

 One-sixteenth natural size. 



and Torosaurus latus or T. gladius, as shown 



in the accompanying figures. It is broad 



anteriorly and narrows posteriorly. The 



posterior and inferior border is undulating 



and supported six small pointed dermal 



ossicles (epoccipitals), as shown in fig. 10. 



The external surface for some distance inside 



this border is very gently concave, but above 



this it is uniformly convex. The parietal 



suture is open throughout the entire length 



of the bone, and the parietal border is heavy. 



Anteriorly the squamosal is in contact with 



the quadrate, the exoccipital, the jugal, and 



the postfrontal, and for a limited extent 



with the quadratojugal, besides sending a 



strong process underneath the parietal. It 



overlaps the external surfaces of all these 



bones and has a very extended contact, 



especially with the postfrontal; through 



which it forms the chief support posteriorly 



and interiorly to the massive supraorbital 



horn. On the inner side, near its anterior 



end, the surface of the squamosal is crossed obliquely by a heavy ridge of bone, presenting 



anteriorly an abrupt shoulder, against which the distal extremity of the exoccipital process 



Fig. 13.— Superior view of parietal of type of Monoclonius crassus, No. 3998, 

 American Museum of Natural History, sqs, Surface for articulation 

 with squamosal; pfs, surface for postfrontal. One-eighth natural 

 size. 



