o. (\ Marsh— Characters qf th< Ceratopsidax 419 



The transverse bones give a weak support to the auxiliaries, 

 which are strengthened by close union with the pterygoids. 

 They meet the pterygoids "behind, and the palatines in front. 



The Brain. 



The brain of Triceratops appears to have been smaller in pro- 

 portion to the entire skull, than in any known vertebrate. Its 

 lion and relative size are shown in Plate 7, fig. 1, / A 

 side view of the brain-cast of another specimen is shown in 

 Plate V, fig. 2, one half natural size. 



The position of the brain in the skull does not correspond 

 to the axis of the latter, the front being elevated at an angje 

 of about thirty degrees, or somewhat more than is indicated in 

 Plate V, fig. 2. . 



The brain-case is well ossified in front, and in old animals, 

 there is a strong septum separating the olfactory lobes. 



Rostral Bone. 



This bone, which has already been described by the writer, 

 is well shown in Plate V, figs. 3, 4 and 5. Although firmly 

 coossitied with the premaxillaries in this specimen, the suture 

 uniting them is quite distinct. In this species, the rostral bone 

 is verv large, and unusually sharp in front. The pre-dentary 

 bone that meets it below is" also very sharp, with corresponding 

 massive dimensions. 



Nasal Horn-core. 



This protuberance is a separate ossification, and is free in 

 youno; animals. It varies much in shape and position, in differ- 

 ent species. In Triceratops prorsus, it is directed nearly for- 

 ward, as shown in Plate Y, figs. 3 and 4. In adult animals, it 

 unites with the nasals, and slightly with the premaxillaries, and 

 in old animals, the suture is entirely obliterated, as in the 

 present specimen. 



Teeth of Triceratops. 



The teeth of Triceratops and its near allies are very remark- 

 able in having two distinct roots. This is true of both the 

 upper and lower series. These roots are placed transversely 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 shown 

 in Plate YI, figs. 1-4. 



The teeth form a single series only in each jaw. The upper 

 and lower teeth are similar, but the grinding face is reversed, 

 being on the inner side of the upper series, and on the outer 

 side of the lower series. The sculptured surface in each series 

 is on the opposite side from that in use. 



