EOCERATOPS CANADENSIS. 
7 
In the type specimen of B. dawsoni the large backwardly curved 
nasal hom-core exhibits this division in the median line at its 
base and for a short distance upward into the hom-core, but 
above this all trace of it is lost. Also in this particular hom- 
core ( B . dawsoni ) there is a very definite demarcation traceable 
between the anterior ossifications (epinasals) and the nasals 
(Plate X, figure 4). In the growth of the ceratopsian nasal 
hom-core an early union took place between the epinasal bones 
and between them and the nasals. 
In Mr. Gilmore’s paper on B. montanensis , in figure 1A on 
page 4, a definite curved groove is shown, in the anterior part of 
the nasal hom-core at its mid-height, which is strongly suggestive 
of the upper boundary of the epinasal ossification. If this 
groove represents what remains of the upper part of the suture 
between the ossification and the nasal the union of the lower 
portion of the former bone with the nasal had, judging from the 
figure, already taken place without leaving a trace of the lower 
portion of the suture (Plate X, figure 3). 
Attention has already been drawn to the extension of the 
nasal forward over the epinasal in the type of Eoceratops which 
evidently represents an individual not fully adult. It is probable 
that in the growth of the ceratopsian nasal hom-core the nasals, 
with increasing age in the individual, contributed an increasing 
share to the formation of the hom-core, the epinasals remaining 
of relatively small size and acting apparently as an anterior 
basal support to the nasal contribution. In comparing the rel- 
ative proportions of the nasal and epinasal bones in the hom- 
core of E. canadensis and of B. montanensis (Plate X), keeping 
in mind differences that may be due to individual age in distinct 
genera, it is seen that in the type of the latter species the nasal 
contribution to the hom-core is much larger than in the former. 
Also in the nasal hom-core of B. dawsoni (Plate X) the proportion 
supplied by the nasals is preponderant, the epinasals entering 
into the formation of the hom-core only as small anterior but- 
tresses. 
The squamosal (Plate I) has been already described in some 
detail in two papers published in 1904. 1 It is irregularly tri- 
1 Op. cit., p. 1. 
