. There are thus, on the lateral surface of th e skull of Scorpaena, two separate depressions in
each of which certain of th e levator and adductor muscles of th e visceral arches have the ir origins,
and th e anterior one of th e two seems certainly to have been developed in some relation to the
muscles th a t have their origins in it. With the posterior depression, this causal relation is much less
evident, and it would seem as if th e anterior depression of Scorpaena must be superimposed upon
the posterior one to form th e subtemporal fossa of Sagemehl’s and Ridewood’s descriptions of the
Cyprinidae. Sagemehl says th a t this fossa in these la tte r fishes is formed as the result of th e origins
of certain of th e levator muscles on this particular p a rt of th e skull, and h e says th a t, in th e Barbidae,
the adductor operculi arises in th e anterior p a rt of th e fossa, and the external levator of th e fourth
arch in its posterior portion. Of th e o ther Cyprinidae he simply says th a t the levators of the branchial
arches, arise from the side walls of th e skull below th e adductor hyomandibularis and adductor
operculi. Ridewood says (’04 a, p. 62) th a t, in certain of these same fishes, th e fossa serves ,,for the
lodgment of the g reat muscles, which by pulling up the inferior pharyngeal bones (fifth ceratobranch-
ials) bring th e te e th upon those bones forcibly against th e callous pad th a t is carried on th e under
surface of th e basioccipital bone“ ; and Vetter says (’78, p. 505) th a t, in Cyprinus and Barbus, th e
levatores arc. branch, externi have the ir origins in p a rt in this fossa, th a t they are in p a rt inserted
on the hind surface of the outer corner of th e large inferior pharyngeal bone, and th a t they press
th a t bone against the bony plate on th e under surface of th e basioccipital. I t seems, accordingly,
to be to certain of the external levators alone th a t th e fossa-forming quality is a ttributed, and when
th ey happen to have their points of origin on th e side wall of the skull in th e region of th e sub-
triangular depression of Scorpaena, they apparently may cause a deepening of th a t depression and
so give rise to a tru e subtemporal fossa. The subtriangular depression of Scorpaena would accordingly
seem to be a rudimentary fossa, and may be called th e subtemporal depression. In the Barbidae
and Homaloptera th is depression is deepened to such an extent th a t th e epiotic is seen a t the b ottom
of it (Sagemehl, 91, p. 554); while in Elops, according to Ridewood, th e supraoccipital also is there
exposed.
Immediately ventral to the surface of origin of the adductor hyomandibularis, on the dorsal
portion of the bulla acustica, a large bundle of the muscles of the trunk has its origin.
T H E O R B I T .
The orbit is large. The interorbital septum is cartilaginous in its anterior and larger portion,
but membranous in its posterior portion. The ventral half of this membranous portion is attached
posteriorly to the anterior edge of the pedicle of the basisphenoid. Above the dorsal end of th a t
pedicle, the membrane spreads laterally, on either side, and is attached to the- anterior edge of the
body of the basisphenoid, and, above th a t bone, to the ventral edge of the alisphenoid and then to
the ventral edge of the ventral process of the frontal ; the membrane thus closing the orbital opening
of the brain case. This membrane is pierced, on either side, and immediately above the basisphénoid,
by the optic nerve. Slightly above the optic nerves, the two oflactory nerves enter a small median
pocket in the membrane, from which a membranous tube leads forward on either sidè of the interorbital
septum. Having traversed this tube, the olfactory nerve of either side continues forward,
in the orbit, lying along the lateral surface of the cartilaginous portion of the interorbital septum
and so reaches and then traverses the olfactory canal through the ectethmoid. Lateral to the olfac-
torius, and along, or enclosed in, the ventral edge of the alisphenoid, the trochlearis enters the orbit.
O R B I T O S P H E N O I D .
There is no orbitosphenoid.
A L I S P H E N O I D .
The alisphenoid is sub-oval in outline. Its dorso-anterior th ird or half is overlapped externally
b y the posterior portion of th e ventral process of the frontal. Its dorsal edge is capped with cartilage,
an d this cartilage rests against th e ventral surface of th e frontal immediately internal to th e ventral
process of th a t bone. The anterior edge of th e bone is presented mesially and b u t slightly forward,
a n d suturates w ith the ventral flange-like process of th e frontal. Its posterior edge is presented laterally
and b u t slightly backward and is bounded, in its dorsal portion, by the sphenotic and the body of
th e prootic, b u t is separated from both of those bones b y a line of cartilage. The ventro-posterior
oorner of th e bone suturates, without intervening cartilage, with the dorso-anterior edge of the
prepituitary portion of th e mesial process of th e prootic and with th e antero-lateral corner of the
body of th e basisphenoid. Its ventral edge forms p a rt of th e boundary of the orbital opening of
th e brain case and gives a ttachment to th e membranes th a t, in the recent state, close th a t opening.
On the internal surface of th e alisphenoid, near its anterior edge, a ridge runs downward a
■short distance from th e dorsal edge of th e bone. This ridge is continuous with a similar ridge on the
corresponding surface of the cartilage th a t caps the bone, and is also continuous with, or is slightly
overlapped by, th e little ridge and process, already described, on th e ventral surface of th e frontal.
The entire ridge thus formed, forms the posterior boundary of what I have referred to as the forebrain
recess of the cranial cavity, th a t recess thus lying mainly anterior to the alisphenoid, and the
alisphenoid bounding th e mid-brain region.
A small foramen is always found perforating the alisphenoid, and th e ventral edge of the
bone, where it bounds the orbital opening of th e brain case, is always notched to form an imperfectly
•closed and larger foramen. The small foramen transmits a small nerve accompanied by two small
arteries; the nerve being a branch of th e ophthalmicus lateralis destined to innervate organ 6 of the
supraorbital canal, b u t accompanied by other fibers, probably general cutaneous, and the arteries
being, one a branch of th e external carotid and th e other a branch of a blood vessel to be later
described as th e vessel x and th a t would seem to represent, in p a rt a t least, the hyo-opercularis
•artery of my descriptions of Amia. The notch in the v entral edge of the bone transmits the nervus
trochlearis. Dorso-anterior to this notch, and close to it, a smaller notch transmits a b ranch of the
orbito-nasal vein. In Amia, this small vein perforates th e alisphenoid, and in my descriptions of th a t
fish I called it the anterior cerebral vein. In Scomber a corresponding foramen was found in the
alisphenoid, and 1 assumed th a t it transmitted a corresponding vein, as it doubtless does. In
Ophiodon, Allen (’05) does not describe this vein, b u t it would seem as if it must there be found
for I find it in Cottus, Trigla, Peristedion and Dactylopterus as well as in Scorpaena, b u t perforating
the alisphenoid in all those fishes instead of passing across its anterior edge. I t would
seem, even, to have a certain morphological importance, though what it may be I can n o t y e t determine.
It, or the foramen th a t transmits the branch of the external carotid, or these two foramina
together, may perhaps represent the foramen spinosum of human anatomy.
On the outer surface of the posterior portion of the alisphenoid, and extending to its ventral
•edge, there are two more or less developed ridges. The postero-lateral one of these two ridges is often
wholly wanting, the antero-mesial one being present, more o r less developed, in all m y specimens. The