12 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 



Family CERATOPSIDAE 



Genus BRACHYCERATOPS Gilmore 



BKACHYCERATOPS MONTANENSIS Gilmore 



A disarticulated skull and a few bones of the skeleton obtained by 

 the 1935 Smithsonian expedition in northern Montana is clearly refer- 

 able to the genus Brachycerato'ps. It is of interest in displaying for 

 the first time some of the adult skeletal features of this genus. This 

 specimen is nearly twice the size of the type on which the genus was 

 establislied, and it further demonstrates the very young character of 

 tliose materials. 



Although the generic relationship is clear, there may be some ques- 

 tion as to its specific affinities, but for the present I shall regard it 

 as belonging to Brachyceratops montanensis^ attributing to more 

 advanced age such differences in structure as are observed between it 

 and the type. The specimen was found about a mile distant from 

 the spot where the type was discovered, and on the south side of Milk 

 River at approximately the same level in the formation. 



Tlie following elements of the skull and skeleton (U.S.N.M. No. 

 14765) were recovered : Right half of the frill lacking the squamosal; 

 articulated left postorbitai, jugal, postfrontal and prefrontal, lachry- 

 mal and supraorbital; right maxillarj'^ containing several teeth; left 

 premaxillary, rostral, a portion of the right half of the nasal horn 

 core; fragment of the basioccipital ; unidentified skull fragments; 

 both femora, left scapula, first rib; one dorsal vertebra and two 

 phalangial bones. 



This is the first undoubted Brachycerato'ps specimen to be found 

 since the discovery of the types in 1913, and it now enables me to 

 make several corrections in the restoration of the skull published in 

 1914. Furthermore, several skull elements not present in the type are 

 here described '' for the first time. 



It is in the frill that the greatest growth changes have taken place, 

 and attention is especially directed to the presence of a series of well- 

 developed processes projecting outward from the border of the frill 

 (fig. 10). In my description of the frill of the type specimen,^ it 

 was pointed out that there were "no epoccipital bones on the margins 

 of the frill but a series of prominences on either side of the median 

 emargination gave the periphery a peculiar scalloped effect." In 

 the light of the specimen now before me it is evident that these prom- 

 inences were the incipient processes so prominently developed in the 

 adult skull. It further substantiates my original statement that there 



"^ Gilmore, C. W., Smithsonian Misc. Coll., vol. 68, No. 3, pis. 1, 2, 1914. 

 8 Gilmore, C. W., U. S. Geol. Surv. Prof. Paper 103, p. 12, 1917. 



