282 SHUFELDT. [Vot. II. 
+.) 
column of bone, antero-posteriorly compressed, and an expanded 
inner portion, which latter is reénforced by radiating projections 
that converge to meet at a point at the lower part of the inner 
margin of the columnar portion. It is hardly necessary to state 
that these prefrontals form the externo-lateral parts of the ante- 
rior orbital wall, the ethmoid completing it mesially. 
Coming now to the vomer (Vo), we find it to be a thin scale- 
like bone, of a form best shown in Fig. 4. It rests in the 
longitudinal excavation of the anterior and lower side of the 
parasphenoid, while its firmest attachment to that bone seems 
to be by the periphery of its anterior margin. 
The parasphenoid (P7.S.) is gently arched as it spans the 
orbital space below, having its convex arc downwards. The 
lower side of this part of the bone, as I have already intimated, 
is longitudinally scooped out, while the upper side presents lat- 
eral surfaces, which are inclined so as to meet in a median line. 
Posteriorly, the parasphenoid makes the usual teleostean con- 
nections with the basioccipital, basisphenoid, and prodtic, being 
deeply cleft as it passes to cover the under side of the first- 
named element (Fig. 4). 
Occupying its usual position, the daszsphenord (Bs) not only 
develops the median process (Fig. 2) seen in so many true 
teleosts, but furnishes a firm horizontal roof for the three-sided 
pyramidal eye-muscle canal, the lateral walls of which are com- 
pleted by the prodtic and parasphenoid. 
As in the majority of osseous fishes, the fvodtic is a well- 
defined and important element at the lateral aspect of the brain- 
case (Pr.O.). Its anterior margin is pierced by the foramen for 
the trigeminal nerve, from which point faint lines in the tissue 
of the bone are seen to radiate. 
The basioccipital (4s) has its thickened and longitudinal por- 
tion underlying the brain-case, as in most fishes, being com- 
pleted behind the facet for the leading vertebra of the spinal 
column. This facet is comparatively rather small, with its con- 
ical depression very deep. 
At either of its sides the basioccipital develops an upturned 
and semicircular plate of bone, similar in structure to the other 
flat bones of the lateral cranial walls, which articulates with the 
lower margin of the opisthotic and the posterior margin of the 
prootic (Fig. 2). 
