69 



In the larger specimen the anterior end is produced forward and is slightly elevated 

 terminating in two projections; the surface is here distinctly nodose. In the lateral, 

 posterior, upper surface a similar rugosity is apparent. The surface of the central con- 

 vexity is smooth. 



In the smaller specimen the upper surface is smooth and pitted throughout. It is 

 trilobed posteriorly and is not produced forward in front where, however, two small nodes 

 occur, one on each side of the median line. 



The structure of the lower surface is marked by a number of smooth, concave areas, 

 as represented in the reproductions, from photographs of the specimens, in figs. 2 and 5 

 of plate XXI. 



It is probable that these bones were situated in the median line of the head, in ad- 

 vance of the nasals. They may have belonged to a species of dinosaur not otherwise 

 represented in the collections from Red Deer river and, judging from the difference in shape 

 of the two specimens, more than one species may be indicated. Marsh in his figure of the 

 head of Triceratops serratus'^ shows a nasal horn core (divided both transversely and 

 longitudinally by sutures) that may correspond to the specimens from Red Deer river. 



A third specimen, similar to the anterior half of the larger of the two bones was col- 

 lected in 1901. It has separated from its posterior half along the line of the transverse 

 suture. 



For these bones the name Stegoceras validus is proposed with the hope that future 

 discoveries may aid in a clearer understanding of their affinities. 



Belly River series, Red Deer river. 1898, 1901. 



TRACHODONTID^. 



Tbaghodon, Leidy. 



Trachodon (Pteeopelyx) selwyni. Sp. uov. 



Plate III, figs. 2 and 3. 



This species is established principally on the evidence of teeth, of which a number 

 from the lower jaw are shown on plate III. The teeth follow each other, quincuncially 

 in the usual Trachodont manner, three or four occurring in the vertical series, but seven 

 or eight can be counted obliquely. They replace each other from the inside and appear 

 in the grinding surface in two or three functional rows. "When three teeth belonging to 

 the same vertical row are in use in the grinding surface at the same time (see fig. 3 of 

 plate III), the outer one is generally worn down to the root and the stump is ready to 

 fall out, the middle one is about half worn down, whilst the inner one is either just 

 coming into use or is only slightly worn. 



The teeth of this species differ from those of T. mirabi/is, Leid}'-, in being rounded 

 oval above, instead of terminating in a point. They are smooth in both species. A few 



*Amer. .Jour. Sci. and Arts. vol. XLin, pi. iii, tig. 4. 1892. 



