ANATOMY OF BALDEN OPTEEA EOSTEATA. 
209 
be the representative of the anterior clinoid process. The optic foramen was situated 
on a plane anterior to the sphenoidal fissure, which latter was formed by the frontal 
and sphenoid bones. Anterior to the optic foramina and groove a slight ridge extended 
transversely, in front of which the ethmoidal process was continued forwards to the pos- 
terior border of the cribriform plate of the ethmoid bone. The inferior surface of the 
basisphenoid was connected behind with the basilar process of the occipital ; in front it 
was overlapped by the posterior expanded part of the vomer, and the alisphenoid 
covered it on each side ; laterally it was concealed by the mastoid and alisphenoid bones, 
with the exception of a small irregular-shaped portion situated in the temporal fossa 
between these latter and the parietal bones. 
The parietal bone was irregularly quadrilateral in outline, having two surfaces and 
four edges. The external or temporal surface was concave posteriorly and convex in 
front, and formed the inner wall of the temporal fossa. The superior surface was convex 
and the most extensive ; it articulated with the occipital, the external table of which 
overlapped it, but its internal table formed with the latter a serrate suture ; more ante- 
riorly this edge became thickened into a small wedge-shaped triangular process, and lay 
between the frontal bone in front and the occipital behind ; from this a flat, thin scale 
of bone was continued forwards lying on the outer side of the frontal, on which it gradu- 
ally attenuated to its anterior edge. Some of the small lamellae of this bone that indi- 
gitated with similar plates on the side of the occipital, anteriorly approached their fel- 
lows of the opposide side, but did not come into actual contact. The posterior edge 
was thicker and almost straight, and was situated at the posterior part of the temporal 
fossa ; it extended downwards and forwards, and united by a plane edge with the ante- 
rior margin of the squamous plate of the temporal bone. The inferior edge was the 
shortest ; it ran forwards to articulate with the small lateral part of the basisphenoid 
(before described) that formed a portion of the inner wall of the temporal fossa ; from 
this the margin was continued downwards and forwards to articulate with the upper edge 
of the great wing of the alisphenoid, which was overlapped by it posteriorly, but in turn 
was more superficial in front. The anterior inferior border was deeply hollowed for the 
reception of the orbital plate of the frontal, and was continued forward as the thin scale 
of bone before mentioned, that ended in the blunt anterior angle. The inner or cere- 
bral surface was concave, and formed a large part of the superior lateral boundary of the 
cranial cavity. 
The ethmoid bone consisted, first, of a cerebral surface, or cribriform plate, Situated 
between the frontal and sphenoid bones ; it presented a median ridge (crista-galli), on each 
side of which existed three or four deep depressions perforated by foramina for the exit 
of the olfactory nerves. Secondly, in the interior of the nares it presented four irregularly 
shaped turbinated bones that were situated internal and superior to the nasal canals ; 
these bones were soft and spongy, and were separated from each other by three meatuses 
posteriorly, but anteriorly they communicated in common with the air-passages. Thirdly, 
the ethmoid presented an orbital surface or os planum situated beneath the orbital plate 
mdccclxviii. 2 H 
