and it projects ventro-mesially into the cranial cavity of the prepared skull and terminates with
a free edge.
The hind edges of the two legs of the alisphenoid are in contact with the anterior ¿dges of
corresponding plates of bone on the ventral edge of the orbital portion of the proôtic; and these two
plates of this part of the proôtic may for convenience be called the parasphenoid and basisphenoid
legs of the orbital part of th a t bone. The basisphenoid leg corresponds to th a t part of the external
surface of the proôtic of Scorpaena th a t forms the mesial wall of the jugular groove on the orbital
surface of the bone; the parasphenoid leg corresponding to the membrane that spans th a t groove
and was referred to, when describing Scorpaena, as a membranous anterior extension of the lateral
wall of the trigemino-facialis chamber. This membrane having ossified, in Cottus, as part of thé
proôtic, the jugular groove of Scorpaena becomes, in Cottus, a canal which opens anteriorly into the
cranial cavity, while posteriorly it opens by a foramen-like opening onto the external surface of the
proôtic. The anterior end of the canal is much larger than its posterior end, and the canal is continuous
anteriorly with the Y-shaped space between the two legs of the alisphenoid, the two spaces
together forming a recess in the cranial cavity which may be called the internal jugular recess. The
internal jugular vein and the truncus ciliaris profundi enter this recess a t its anterior end, and, running
posteriorly, issue through the foramen-like opening a t its hind end. This latter foramen is accordingly
an internal jugular foramen, but it is not the strict homologue of the foramen th a t I have described
as the internal jugular foramen in one specimen of Scorpaena; for the foramen in Cottus is bounded
by the proôtic and the parasphenoid alone, while in Scorpaena it is bounded by the alisphenoid,
the proôtic and the parasphenoid. The foramina in the two fishes result, however, from the
bridging of one and the same canal by a bridge of bone th a t is narrow in one fish and wide in
the other.
On the internal surface of the alisphenoid of Cottus, there is, as in Scorpaena, a brace-like
flange, which lies between the fore-brain and mid-brain recesses of the cranial cavity. In Cottus
this flange is thin and tall and forms, with a corresponding flange on the ventral surface of the frontal,
a somewhat important partition between the dorsal corners of the two recesses.
The alisphenoid is perforated, in its antero-ventral portion, by a foramen which varies considerably
in position in my specimens. I t transmits the lateralis nerve destined to innervate the 6 th.
or terminal organ of the supraorbital canal, the nerve always being accompanied by a blood vessel.
Whether other than lateralis fibers form part of the nerve was not investigated. The nervus troch-
learis passes across the free edge of the alisphenoid without perforating it.
The SPHENOTIC is normal in position and forms, as usual, the dorsal portion of the facet
for the anterior articular head of the hyomandibular and the anterior portion of the dilatator fossa.
The oticus canal enters the bone on its orbital surface, and traversing the bone opens into the bottom
of the dilatator fossa. A flange on the cerebral surface of the bone forms part of the anterior bounding
wall of the labyrinth recess. The dorsal surface of the bone is almost entirely covered by the frontal
and pterotic, comes nowhere to the level of the dorsal surface of the skull, and gives support to a
part only of the dorsal edge of the postfrontal.
The PROOTIC differs in certain important respects from the bone in Scorpaena and Sebastes.
One of these differences is the enclosing of the internal jugular groove’ and has just above been described.
The other relates to the trigemino-facialis chamber, and is described below. The boïie is
W ro fe a as usual by t i e sphenotie*. pterotie; éxoecípital and basieecipital, and its ventral portion
is overlapped externally by t i e parasptenoid. From t i e opistiotie it is separated by a considerable
interval.
Immediately anterior to the base of the postorbital process, the proótic is perforated by two
or three foramina, which transmit the profundus, trigeminus and facialis nerves: the profundus
issuing alone through one of the foramina, where there are three, but issuing with the trigeminus
where there are but two. The profundus foramen,-when present, is a small canal which, running
inward, either opens into the trigeminus foramen, or close to that foramen on the inner surface of
the skull. The trigeminus foramen is ’the largest of the two or three and lies antero-dorsal to the
facialis foramen, both foramina opening into a trigemino-facialis recess on the internal surface of
the proótic, similar to the recess described in Scorpaena. This recess in Cottus is, however, relatively
larger than in Scorpaena, and its floor as well as its roof is formed by a thin shelf-like flange of bone.
The recess lodges, as in Scorpaena, the profundus ganglion and the ganglia formed on the communis
and lateralis roots of the trigemino-facialis complex. The communis ganglion is a large, pear-shaped
ganglion, and from it, two intracranial nerves arise. One of these nerves is the ramus palatinus facialis,
which runs downward forward and mesially, perforates the horizontal ledge that forms the floor
of the trigemino-facialis recess and then the prepituitary portion of the mesial process of the proótic,
and so enters the myodome at its extreme dorso-lateral corner. The other nerve runs upward and
backward, perforates the thin shelf of bone that forms the roof of the trigemino-facialis recess, and
then continues upward and backward along the edge of the bony anterior wall of the labyrinth recess,
until it reaches the roof of the cranial cavity. There it turns backward and mesially along the internal
surfaces of the frontal and parieto-extrascapular, passes between those bones and the supraoccipital,
and issues on the dorsal surface of the skull close to its hind edge and close to the median line. On
mie- side of the one specimen examined, the thin roof of the trigemino-facialis recess was perforated
by two foramina, the communis nerve just above described there ■ doubtless arising from its
ganglion by two strands. This nerve, in its general course, closely resembles the so-called lateralis
accessorius of Gadus and Silurus, and, like the palatine, must consist largely, if not entirely of
communis fibers.
In addition to these two intracranial nerves, two large nerve trunks and the smaller truncus
ciliaris profundi arise from the complex and issue by the two or three foramina, in the proótic.
One of the two trunks is the root of the trigeminus accompanied by lateralis and communis
fibers, and this root is closely accompanied by the truncus ciliaris profundi. The other trunk is the
root of the facialis accompanied by lateralis and communis fibers. The truncus ciliaris profundi separates
from the root of the trigeminus while still inside the cranial cavity and either issues through
the trigeminus foramen, or through a separate and independent profundus foramen. I t then enters
the internal jugular canal through its posterior opening, and traversing th a t canal enters and traverses
the anterior end of the myodome, and so issues in the orbit. The root of the trigeminus swells into
a ganglion either as it traverses its foramen or wholly but immediately beyond that foramen, the
trigeminus ganglion thus being largely or wholly extracranial in position. The facialis passes close
to the hind end of this extracranial ganglion, and, as in Scorpaena, receives from its hind end a large
communicating branch. Associated with the trigeminus ganglion and lying immediately ventral
to it, there is, as in Scorpaena, á large sympathetic ganglion, but this ganglion here lies on the external
surface of the proótic. The jugular vein and external carotid artery both come into the same rela>
Zoologies. Heft 67.