278 SHUFELDT. [Vor Ue 
this process, the posterior border of the frontal shows at least 
one conspicuous notch, while its free margin overlaps the supra- 
occipital, and is in turn overlapped by the parietal (Pa) more ex- 
ternally (Fig. 2). | Mesially, its surface turns upwards, more 
particularly behind, where with the fellow of the opposite side 
it grasps in the middle line the anterior portion of the supraoc- 
cipital crest. Below this point the two frontals have their 
straight, free, mesial edges roughly in contact with each other, 
and slope gradually downwards to the margin of that concavity 
which is found in front (Figs. 2 and 3). 
This extraordinary fossa on the anterior aspect of the cranium 
of Grammicolepis is entirely open above; its rugose and subcir- 
cular margin being formed by the frontals; while below it 
becomes conical with its apex in the middle line, and in the eth- 
moid. Above, where it is most capacious, it has its posterior 
wall formed by descending plates developed on the part of the 
frontals, the left one considerably overlapping the right. Below 
this, in the middle line, there is an opening of some size, which 
leads into a commodious chamber lying between the frontals 
above and the mesethmoid below. 
A frontal is truncate in front, where it overhangs the corre- 
sponding prefrontal, and internally articulates with the curiously 
shaped ethmoid. Behind this, and on its under side, it forms the 
major share of the roof of the orbit. Then occurs a longitudinal 
keel, which separates this from that other part of its under 
surface which forms the roof of the mid-chamber described in 
the last paragraph. Viewed together from above (Fig. 3), it 
will be observed that the rugosities of the frontals are limited 
behind by a subparabolic curve with its arc anteriorly directed. 
In this dried cranium a farietal (Pa) is represented by a 
thin, flake-like, semi-transparent piece of bone, of a form shown 
in Fig. 3. To the outer side of its mid-longitudinal line it de- 
velops for its entire length quite a prominent, though thin, crest, 
which is rugose all along its superior margin. 
The anterior three-fifths of the under surface of this element 
simply rests upon the frontal and supraoccipital, while the re- 
maining portion behind is more firmly attached, and really holds 
the bone.in its position. Its outer free margin articulates prin- 
cipally with the inner border of the posterior prolongation of 
the corresponding frontal, though still more posteriorly it meets 
