BRACHYCF.RATOPS MONTANENS1S 101 



"The centrum of the rirst or sacrocaudal ... is longer than wide and has an articular facet on 

 its superoantero lateral angle for the articulation of the last sacral rib. The neural arch, although 

 poorly preserved, indicates that the spine was distinct from the spines forward of it. . . . 1 he anterior 

 and posterior zygapophyses are also differentiated, not coalesced, as in all preceding sacral vertebrae. 

 The diapophyses on the first and second caudals are given off from the sides of the arch well below 

 the zygapophyses but above the neurocentral suture, but that on the fourth caudal is below that 

 suture." Thence backward to caudal 25 the diapophyses are borne on the centra of their respective 

 vertebrae, although bearing somewhat on the pedicels of the arch until the 20th is reached. 



There is nothing particularly distinctive about either the pectoral arch or fore limb, except 

 perhaps the slenderness of the preserved elements. The coracoid and humerus are unknown as yet, 

 which is also true of the carpus. A few phalanges of the manus are preserved. 



The ilium is peculiar as compared with that of Monoclonius and Triceratops. It is not only 

 much smaller, but the transverse expansion of its anterior plate, the greater inclination outward of 

 the crenulated outer margin, and the differentiation of the thickened deflected border above the 

 ischiac peduncle are all distinctive from described forms, including Pentaceratofs. The pubic 

 peduncle is rather slender, but the ischiac peduncle is relatively very heavy. 



The dimensions of the left ilium of the paratype, No. 7953, U.S.N. M. are as follows: 



Length over all 362 mm. 



Width of anterior blade 65 



Transverse width at center 



Depth of posterior blade 37 



Depth at center of acetabulum 51 



The pubis is not unusual. The ischium is a long, slender, slightly curved bone with an expanded 

 proximal end which bears a heavy articulation for the proportionately massive pubic peduncle. The 

 bone compares in curvature with that of Monoclonius {Centrosaurus), and contrasts sharply with 

 that of Pentaceratofs and Triceratops. 



The ratio of tibia to femur in Brachyceratops is as 1: 1.28; while in Triceratops it is 1: 1.59, 

 and in Monoclonius {Centrosaurus) 1: 1.43. That is, in the first, the femur is about one-quarter 

 longer than the tibia, in the others it is one-half longer. May this not be another juvenile character? 



Dimensions 



Femur (No. 7953) Tibia (No. 7957) 



Greatest length 337 mm. 268 mm. 



Greatest width 



Proximal end 100 99 anteroposteriorly, estimated 



Distal end 83 30 



Least width of shaft 45 



There are two distal tarsals in addition to the astragalus and calcaneum. The former are "irregu- 

 larly rounded discoidal elements with upper surfaces concave and lower convex. . . . The largest 

 articulates with the proximal end of metatarsal II, the smallest with metatarsal III, ... to which it 

 was found securely attached by matrix. The third tarsal was wholly in apposition to metatarsal 



IV."" 



The metatarsals were four functional and one vestigial, as in Monoclonius {Centrosaurus), and 

 the general appearance of the entire foot is comparable. 



The complete skeletal restoration of Brachyceratops (PI. IX, B), erected in the United States 

 National Museum in 1922, was the first attempt to mount one of the earlier Ceratopsia, and it is a 

 highly commendable result, viewed in the light of later finds. The skeleton is composite, with such 

 elements as were not present in the collection modeled preferably from Judith River forms. The 



u 



Loc. cit., p. 33. 



