EOCERATOPS CANADENSIS 
3 
ation of its exact length being the premaxilla, the rostral bone, 
and the median portion of the neck-frill. The restored outline 
indicates a short, heavily built head, in which the total depth 
from the upper surface between the supraorbital horn-cores 
to the lower margin of the dentary, is slightly over one-third 
of the length from the front edge of the rostral bone to the back 
border of the frill. 
Eoceratops thus appears to have had a short skull, compact 
and deep in front, and tapering behind as seen in side view. 
The lower jaw is robust, the nasal bones are remarkably deep, 
and the supraorbital horn-cores are large in comparison with 
the inconspicuous nasal hom-core (Plate I). This compactness 
of the anterior half of the skull with great depth is also found in 
Brachyceratops, a form in which the nasal horn was the principal 
weapon of defence. In comparison with Eoceratops the later 
Triceratops has lengthened the face and added greatly to the 
size of the supraorbital horn-cores to the neglect of the nasal 
horn. In Diceratops with the enlargement of the brow-horns 
there is the concomitant non-development of the nasal one. 
The supraorbital horn-core rises from above the orbit, so as 
to overhang the latter’s anterior half, its front convexity at 
mid-height being almost directly above the anterior surface of 
the rim of the orbital opening. The horn-core tapers to a point 
and throughout its length is circular in cross section, except near 
the base where there is a very slight flattening above the orbit 
and a feeble lateral compressiononthe antero-exteriorface causing 
the fore and aft diameter to somewhat exceed the transverse one. 
In shape, without considering its direction of growth from the 
head, it very much resembles that of a modem bison, but it is 
shorter, tapers more rapidly, and is less curved than the average 
hom-core in the adult mammal. 
The postfrontal (Plate IX, figure 1) is of irregular shape, 
broad behind and narrow in front with the base of the supra- 
orbital hom-core rising from it slightly in advance of its mid- 
length. The surface slopes gently backward and inward from 
the base of the hom-core in continuation of the concave curve 
of the same. Postero-extemally it is bent downward with a de- 
cided angulation to form a nearly vertical plate of some extent, 
