514 (i EULOGY OF THE DENVER BASIN. 



central region of the skull is thus greatly strengthened to support the enor- 

 mous horn-cores which tower above. These elevations rest mainly on 

 tlif postfrontal bones, 1 >ut the supraorbitals and the postorbitals are also 

 absorbed to form a solid foundation lor the horn-cores. 



These hom-cores arc hollow at the base, and in general form, position, 

 and external texture agree with the corresponding parts of the Bovidse. 

 They vary much in shape and size in different species. They were evi- 

 dently covered with massive, pointed horns, forming most powerful and 

 effective weapons. 



The orbit is at the base of the horn-core, and is surrounded, especially 

 above, by a very thick margin. It is oval in outline, and of moderate size. 



The enormous posterior crest is formed mainly by the parietals, which 

 meet the postfroiitals immediately behind the horn-cores. The posterior 

 margin is protected by a series of special ossifications, which in life had a 

 thick horny covering. These peculiar ossicles, which extend around the 

 whole crest, have been called the epoccipital bones. In old animals they 

 are firmly coossified with the bones on which they rest. 



The lateral portions of the crest are formed by the squamosals, which 

 meet the parietals in an open suture. Anteriorly they join the postfrontal 

 elements which form the bast- of the horn-cores, and laterally they unite 

 with the jugals. The supralemporal fossa' lie between the squamosals 

 and the parietals. 



The teeth of Triceratops and its near allies are very remarkable in 

 having two distinct roots. This is true of both the upper and lower series 

 These roots are placed transverse! \ in the jaw, and there is a separate 

 cavity, more or less distinct, for each of them. One of these teeth from 

 the upper jaw is represented in fig. 78. The teeth in this family are entirely 

 confined to the maxillary and dentary bones. The rostral bone, the pre- 

 maxillaries, and the predentary are edentulous. 



The atlas and axis of Triceratops are coossified with each other, and 

 at least one other vertebra is firmly united with them. These form a solid 

 mass, well adapted to support the enormous head. 'The cup for the 

 occipital condyle is nearly round and very deep. The rib of the second 

 vertebra is coossified with it, but the third is usually free. The centrum 



