18 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 



their counterparts on the opposite side. A portion of the anterior 

 border indicates the horn to have been slightly recurved. The external 

 surface is sculptured by a few longitudinal ramifying vascular 

 grooves. 



The left premaxillary is preserved in almost its entirety. It shows 

 the median septum to be more extensive with a resulting diminution 

 in size of the nareal opening through these bones as contrasted with 

 the original restoration of this part of the skull; also the ascending 

 posterior process is longer and thus extends back farther on the side 

 of the face. It closely resembles the premaxillary of Monoclonius 

 in being short and deep. 



The rostral except for its larger size is in perfect agreement with 

 the rostral of the immature specimens. The outer surfaces are more 

 rugose, a difference naturally expected in an animal of more advanced 

 age. 



The left scapula is nearly twice the size of those found with the 

 typical specimens, but it is in accord with them in all respects. The 

 blade is relatively narrower, especially at the center, than in any of 

 the Monoclonius scapulae with which it was compared. 



The single anterior dorsal vertebral preserved with this specimen 

 agrees in all particulars with those of the type specimen. It shows 

 the same strongly elevated diapophyses with relatively small centrum. 

 The femora are about 580 mm. long, this measurement being uncer- 

 tain because of the crushing to which both have been subjected. On 

 this account they offer no basis of comparison with those of other 

 members of the Ceratopsia, 



In 1933, after reviewing the skeletal characters of the Brachy- 

 ceratops skeleton, Lull ^^ remarks : "The relationship of Brachy- 

 ceratops with other genera is obscure." This study of a nearly adult 

 specimen I believe clears up some of that obscurity. It now seems 

 quite apparent that its closest affinities are with the genus Mono- 

 clonius. The short, deep facial region of the skull; similarities in 

 frill development, especially the sliort squamosal; small brow horns 

 and large nasal horns; and saddle-shaped crest are all features held 

 in common. A summary of the distinguishing skull features of 

 Brachyceratops are as follows : Longitudinal division of the nasal 

 horn ; reduced number of teeth in the dental series ; epoccipital proc- 

 esses outgrowths of the frill not separate ossifications ; greater number 

 of epoccipital processes on the frill; and small fenestra in the frill. 



"Mem. Peabodj' Mus. Nat. Hist., vol. 3, pt. 3, p. 102, 1933. 



U. S. GOVERNMENT PRINTING OFFICE: 1339 



