EOCERATOPS CANADENSIS. 
2 5 
Brachyceratops there is a simple undulation of the frill border. 
In the Belly River Chasmosaurus epoccipitals form a prominent 
feature of the frill armature, but in its supposed descendant 
Torosaurus they have altogether disappeared. 
The supraorbital horn-cores have hitherto been regarded as 
simple outgrowths, and the nasal one as a separate ossification 
from a single median centre. 
As regards the horn-cores Mr. Hatcher, in his monograph, 
pages 32 and 33, has given his views of their origin. This author 
stated that “While these horn cores (nasal)are supported by the 
nasals, and in old animals become firmly co-ossified with them, 
they nevertheless have their origin in separate and distinct 
centres of ossification. Moreover, since in young individuals 
every nasal horn core is seen to have had its origin in a single 
median centre of ossification rather than in two distinct lateral 
centres placed one beside the other, it is evident that this horn 
core is in reality morphologically quite distinct from the nasals. 
In this respect the nasal horn cores differ greatly from the supra- 
orbital horn cores, which are simple outgrowths from the post- 
frontals, and therefore are morphologically a part of their 
supporting elements” . “Morphologically 
the nasal horn cores may be considered as dermal or epidermal 
ossifications similar to the epijugals, epoccipitals, the rostral, 
and the predentary, and as quite distinct from the frontal horn 
cores.” 
As just stated the present writer regards the horn-core 
over the orbit as an ossification separate from the postfrontal. 
With increased age in an individual a union of the base of this 
separate ossification (epipostfrontal) with the postfrontal took 
place with usually a loss later of all trace of the suture. 
The type of Eoceratops throws light on the origin of the 
nasal horn-core. In this specimen this small horn-core is seen 
to be made up of the anterior end of the nasals and a separate 
ossification (epinasal) in front of each nasal, as explained in the 
description of the skull of Eoceratops and shown in the figure 
of that specimen, proving the quadruple origin of the nasal 
horn-core, that is, that there were two separate ossifications 
one in front of each nasal instead of one medium ossification 
anterior to these bones as believed by Hatcher. 
