90 



THE CERATOPSIA. 



The posterior crest is somewhat saddle-shaped. Its sides are wavy, with a slight thickening of the bone in the posterior 

 five of the seven corresponding convexities of the periphery, while a pair of inwardly directed spurs of bone, with their points 

 turned slightly downward, are developed on its posterior border, one on each side of the median line. The intervacuital 

 element is thickened along its median length and a more decided strengthening of the bone occurs along the posterior border, 

 resembling in this respect the corresponding part of Monoclonius belli, described farther on. In all other parts of the crest 

 the bone is thin, more particularly near and at the margin of the fontanelles, whilst along the sinuous curves of the sides the 

 edge is sharp, except in the emarginations, where it is rounded. Vascular markings occur on both surfaces, more particularly 

 on the peripheral projections. 



Measurements. Mm. 



Height of orbit 0. 110 



Width of orbit - . . 095 



Height of horn core '. 331 



Circumference at base of horn core _ 343 



Antero-posterior diameter of base of same . . 135 



Transverse diameter of base of same . 092 



Diameter of occipital condyle 060 



Length of maxilla, approximate — — — 350 



Height of same, approximate 120 



Long diameter of lowejf face of quadrate 080 



Short diameter of lower face of quadrate . 036 



The skull and the posterior crest were collected on Red Deer River in 1901. 



With this species are provisionally associated a scapula and coracoid, a sacrum, an ilium, a rostral bone, and a predentary 



bone, described or referred to in the next succeeding pages. 



The scapula with coracoid is figured 

 on PI. XIX, fig. 4 [PI. XX, fig. 1], 

 viewed from its inner side. 



The scapula is long and narrow, 

 slightly concave inward in the direc- 

 tion of its length, stout below, thin- 

 ning rapidly upward, upper end ter- 

 minating squarely, breadth decreas- 

 ing toward mid-length, slightly ex- 

 panded above, front margin thin, 

 back margin broad below, narrowing 

 to its mid-length, then continuing 

 thin upward. A rounded ridge ex- 

 tends upward, on the outer surface, 

 diagonally across from the upper end 

 of the glenoid cavity to the front 

 margin, continuing as a decided thick- 

 ening of the front margin above. 



The coracoid is broader than high, 

 emarginated below the glenoid cavity 

 and produced backward below, lower 

 border turned inward, inner surface 

 decidedly concave, back border at 

 emargination thick, border elsewhere 

 rather thin, rounded. Foramen trav- 

 ersing thickness of upper part di- 

 rected obliquely downward and out- 

 ward with an enlarged outer opening. A small foramen occurs, below the glenoid cavity, in the emargination of the 



posterior border. Glenoid cavity higher than broad, its curve forming almost a semicircle. 



In the specimen figured the coracoid was probably firmly united with the scapula, the suture between them, extending 



from the mid-height of the glenoid cavity forward, being only slightly indicated. The union of the two bones may be regarded 



as an evidence of age in the individual. 



The left scapula and coracoid from the Red Deer River district, so similar, in most respects, to that of Triceratops 



prorsus Marsh, as figured in Sixteenth Report of the United States Geological Survey, differs in one important particular, 



viz, in having the lower border of the coracoid turned inward instead of outward. 



Fig. 93. — Posterior crest a referred by Lambe to Monoclonius dawsoni, probably pertaining to a 

 distinct species; viewed from beneath. Slightly less than one-eighth natural size. The num- 

 bers give the thickness of the bone, in centimeters, at the points indicated. P, Parietal; S, 

 squamosal; jF, fontanelle. After Lambe. 



o This is the type of Centrosaurus apertus Lambe. See PI. XXIV and footnote on p. 93. 



