134 



THE CERATOPSIA. 



healed without exhibiting any exostosis or malformation. Its present form does not appear to be 

 due to erosion after entombment. Near its distal extremity the surface is marked by a number 

 of rather deep grooves. The horn is ovate in cross section. The humerus and vertebrae found 

 associated with the skull show no distinctive characters. It is very unfortunate that the oppo- 

 site of this horn core can not at present be found anywhere among the collections of the U. S. 

 National Museum, since it evidently afforded the principal characters for distinguishing the 

 species. There are in the collections of that museum, however, two other skulls, No. 4286 and 

 Nos. 1203 and 1206-1210, more or less incomplete, that exhibit grooves on the supraorbital horn 

 cores very similar to those mentioned as shown in the type of the present species. 



One of these, No. 42S6, is shown here in fig. 113, which represents an anterior view of that 

 portion of the skull preserved. In this skull the supraorbital horn cores were large and elongate 

 and bore each a broad and deep groove on the anterior and inner surface, as shown in the figure, 

 instead of on the posterior surface, as was described by Marsh in the type of this species. 



The other skull (Nos. 

 1203 and 1206-1210) men- 

 tioned above is nearly 

 complete, though disarticu- 

 lated. Posterior and an- 

 terior views of the frontal 

 region are shown in PI. 

 XXXVII. These show the 

 horn cores as marked by 

 long grooves, both on their 

 anterior and posterior sur- 

 faces, similar to those de- 

 scribed by Marsh as obtain- 

 ing in the type of the pres- 

 ent species on the posterior 

 surfaces of the horn cores. 

 In view of the fact that 

 as shown above, grooves 

 similar to those described 

 by Marsh as character- 

 istic of the present species 

 may occur at various places 

 on the supraorbital horn 

 cores of the Ceratopsidse, it does not seem advisable to consider either the presence or the position 

 of such grooves as of specific importance. It is probable that such grooves have, in most 

 instances at least, had their origin in an infolding or thickening of the horny sheath with which 

 in life the horn core was incased, and that their position, form, and depth were determined by 

 the plac§, nature, and amount of the thickening or infolding of the horny substance. Such 

 being their origin, as appears not improbable, they are likely to appear in any of the various 

 genera and species, and should not be considered as of specific importance. 



* 



Triceratops elatus Marsh. 1891. • 



Fig. 113 



-Anterior view of trontal region of Triceratops skull, No. 42S6, V. S. National Museum. 

 Referred to T. sulcatus Marsh. One-eighth natural size. 



Type (No. 1201, U. S. National Museum) consists of skull, from Laramie of Converse County, Wyo. 

 Original description in Am. Jour. Sci., vol. 42, September, 1891, p. 265. 

 Osborn, H. F., Contr. Canadian Pal., vol. 3 (quarto), pt. 2, 1902, p. 14. 



