maesh.] TRICERATOPS. 211 



in addition to theii - strong union with the quadrate, send outward a 

 branch, which curves around the end of the maxillary. 



The palatine bones are much smaller than the pterygoids. They are 

 vertical, curved plates, outside and in front of the pterygoids, and 

 uniting firmly with the mamillaries. The vomers join the pterygoids 

 in front, where they appear as thin bones, closely applied to each other. 



The transverse bones give some support to the mamillaries, which 

 are further strengthened by close union with the pterygoids. They 

 meet the pterygoids behind and the palatines in front. 



THE LOWER JAWS. 



The lower jaws show no specialization of great importance, with the 

 exception of the predentary boue already described (PI. LXI, figs. 4-6). 

 There is, however, a very massive coronoid process rising from the 

 posterior part of the dentary (PI. LX, fig. 1). The articular, angular, 

 and surangular bones are all short and strong, but the splenial is very 

 long and slender, extending to the predentary. The angle of the lower 

 jaw projects but little behind the quadrate. 



The skull shown on PI. LIX was discovered in the Ceratops beds of 

 Wyoming by the writer's able assistant, Mr. J. B. Hatcher, who also 

 found many other remains of dinosaurs. 



THE BRAIN. 



The brain of Triceratops appears to have been smaller in proportion 

 to the entire skull than in any known vertebrate. Its relative size is 

 shown on PI. LXXVI. fig. 1. 



The position of the brain in the skull does not correspond to the 

 axis of the latter, the front being elevated at an angle of about 30° 

 (PI. LXI, fig. 7). 



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

 strong septum separating the olfactory lobes. 



Tin-: TEETH. 



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 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, represented by several figures (PL LXI, figs. 

 9 and 10, and PI. LXXYIII, fig. 4), is typical of the group. 



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. 



The teeth are not displaced vertically by their successors, but from the 

 side. The crown of the young tooth, also with two strong roots, cuts its 

 way between the alveolar margin and the adjacent root of the old tooth, 

 but sometimes, as might be expected, advances between the two roots. 



