to be wholly wanting. A deep and narrow incisure, which separates th e process from th e almost
equally tall posterior portion of th e bone, transmits the internal carotid artery. From this incisure
a groove runs upward on th e outer surface of th e prootic, toward th e facialis opening of the trigemino-
facialis chamber, and lodges th e internal carotid artery. Ventral to th e internal carotid foramen
this groove is continued on the outer surface of th e parasphenoid, b u t there simply marks the
posterior limit of th e surface of insertion of th e adductor arcus p alatini. The infrapharyngobranchial
of the first arch has its a ttachment to th e skull anterior to th e groove, in th e immediate neighbourhood
of the internal carotid foramen.
Between, or slightly anterior to the anterior edges of the ascending processes of the pa ra sphenoid
there is, in th e middle line of the dorsal surface of the bone, a pronounced and sharply
pointed process, directed dorso-posteriorly. The anterior edge of this process is grooved, is presented
dorso-anteriorly, and lodges the ventral edge of th e posterior portion of th e cartilaginous interorbital
septum and, dorso-posterior to th a t cartilage, and continuous with it, th e ventral end of th e pedicle
of the basisphenoid. On th e ventral surface of th e bone, slightly anterior to this little process, there
is, on either side, a slight process, or ledge directed laterally, which thus has approximately th e position
of the well developed process of Osteoglossum.
The ORBITS are roofed by th e ectethmoids and frontals, and are separated from each other
by an interorbital septum, the anterior portion of this septum being of cartilage, while its posterior
portion is of membrane. The extreme anterior end of th e septum is perforated b y an opening which
puts th e orbits in communication w ith each other, this opening forming the median p a rt of the anterior
eye-muscle canal. The hind wall of th e orbit is formed by th e alisphenoid, basisphenoid, prootic
and sphenotic, and is slightly reentrant in its lateral portion, this being due to the projecting anterior
edge of the lateral surface of the brain case. The ventral flange of th e frontal being b u t slightly
developed, the orbital opening of the brain case is, in consequence, large and somewhat rectangular
in shape.
The MYODOME has prootic and basioccipital portions, th e la tte r extending only about one
half th e length of th e basioccipital, and opening posteriorly on th e ventral surface of th a t bone by
a small opening only. The orbital opening of the myodome is large and inclines strongly downward
and forward, while th e roof of th e prootic portion, or body of th e myodome inclines strongly downward
and backward. This is due to a deepening of th e orbits, posteriorly, and a correlated and marked
tilting upward of the mesial processes of the prootics, this giving to th e myodome the appearance
of a large and deep recess a t th e hind end of th e orbits.
There is no ORBITOSPHENOID.
The ALISPHENOID is bounded by th e sphenotic, the frontal, and the prepituitary portion
of th e mesial process of the prootic, the basisphenoid not coming into bounding contact with it. The
antero-mesial edge of th e bone is slightly concave, and bounds the orbital opening of th e brain case.
This edge of th e bone forms a continuous line with th e anterior edge of th e mesial process of the
prootic, and th e adjoining edges of the two bones are cu t away to form a rounded incisure which
transmits the nervus trochlearis. Dorsal to this incisure, in th e anterior edge of the alisphenoid,
there is another incisure, often closed to form a small foramen, which transmits the cerebral branch
of th e orbito-nasal vein. Near th e center of the bone there is a larger foramen which transmits th a t
branch of the ophthalmicus lateralis th a t supplies th e small latero-sensory organ in th e terminal
tube of th e supraorbital canal. This nerve, as in Scorpaena, perforates the alisphenoid, then runs
upward along the inner wall of the skull, traverses the lateral fontanelle, and, perforating the frontal,
reaches its organ. As in Scorpaena; th e nerve is accompanied, as it traverses its foramen, by branches
of the external carotid artery and th e vessel x.
On th e external surface of the bone, near its ventral edge, there is a short and slight ridge which
is continued downward onto the external, ventro-anterior surface of the mesial process, of the prootic.
Toward this ridge a small process projects dorsally from th a t p a rt of the prootic th a t forms the anterior
edge of the lateral surface of th e b rain case, this process being of very variable length, and the process
and the ridge above it being connected by fibrous tissues. That p a rt of the ridge th a t lies on the
alisphenoid represents a slight remnant of the parasphenoid leg of th a t bone, the p a rt th a t lies on the
prootic here replacing a p a rt of th a t process of th e parasphenoid th a t, in Cottus, comes into contact
with the alisphenoid.
On th e internal surface of the alisphenoid, a t about its antero-dorsal quarter, there is a bracelike
thickening of th e bone, which is the greatly developed homologue of the small ridge described
on the internal surface of th e alisphenoid of Scorpaena. The flat dorsal surface of the brace is cartilaginous
in places, reaches the level of th e dorsal edge of th e bone, and abuts against the ventral
surface of th e frontal; the hind edge of this surface of the brace almost reaching the anterior edge of
th e supraoccipital. The lateral edge of the dorsal surface of the brace forms th e mesial boundary of
th e anterior half of the lateral cranial fontanelle, its mesial edge being in synchondrosis with a large,
median postepiphysial interspace of cartilage which extends forward from the anterior edge of the
supraoccipital. The anterior edge of this postepiphysial interspace of cartilage is slightly concave, and
extends from th e anterior edge of th e alisphenoid of one side to th a t of th e other side. From the
antero-lateral corner of the cartilage, a band of cartilage runs postero-laterally along the dorsal edge
of the plate-like body of the alisphenoid, the postero-lateral end of the band being continuous with a
band of cartilage th a t runs backward along the mesial edges of the sphenotic and pterotic and forms
the lateral boundary of the lateral cranial fontanelle. In Trigla gurriardus, a specimen of which was
used for the figure showing a dorsal view of the chondrocranium, there was a deep bay in th e anterior
edge of th e postepiphysial cartilage, much larger and deeper th an th a t found in the specimens of
Trigla hirundo th a t were examined.
The BASISPHENOID has a long pedicle which is directed downward and forward a t an angle
of from 300 to 45 °, th e two wings of the body of the bone being directed laterally and slightly upward.
The bone does not come into bounding contact with the alisphenoid. Along the dorsal surface of the
body of the bone, on either side, th e optic nerve pierces the membrane th a t closes th e orbital opening
of th e b rain case and enters the orbit. Slightly dorsal to the optic nerve, the nervus olfactorius pierces
th e same membrane, and from there runs forward along th e lateral surface of th e interorbital septum,
lying wholly free in the orbit. In the hind edge of th e body of the bone, in juy largest specimen, there
is a median and imperfectly closed foramen which unquestionably transmits the median encephalic
arte ry formed by th e fusion of th e internal carotid arteries of opposite sides of the head.
The LATERAL SURFACE OF THE BRAIN CASE is relatively flat and narrow, and its
anterior edge has a pronounced reentrant angle, a t about th e middle of its height. That p a rt of this
edge th a t lies ventral to th e point of the angle inclines forward and downward and is formed b y a th in
plate of bone which, in its dorsal portion, projects forward considerably beyond the adjoining portion