of the'orbital surface of the brain casé. The postero-ventral portion of the orbit is thus herè bounded
laterally by bone, this part of the orbit leading into and being continuous with the myodome.
The PROÜTIC forms th e middle three-fifths of th e anterior edge of th e brain case, the dorsal
fifth being formed by th e sphenotic, and th e ventral fifth b y th e short ascending process of th e para-
sphenoid. A t th e middle of th e entire edge there is a large foramen which perforates a thm plate-like
portion of th e edge and leads directly into a small recess which lies on th e orbital surface of the proôtic
immediately dorso-lateral to the orbital opening of the myodome. This recess is th e imperfectly
enclosed trigemino-facialis chamber, and th e large foramen th a t opens from it onto the lateral surface
of th e brain case is th e facialis opening of th a t chamber. The lateral wall of th e chamber is reduced
to th e slender column of bone th a t forms th e anterior boundary of th e facialis opening. Anterior to
this column of bone there is, on th e projecting plate-like edge of th e proôtic, a process of variable
length and shape, already referred to, which projects upward toward th e slight ridge on th e orbital
surface of th e alisphenoid. This la tte r ridge, as already stated, represents th e parasphenoid leg of
the alisphenoid, th e process of th e proôtic being a proôtic outgrowth w hich has invaded the alisphenoid
membrane, there replacing, in this fish, th e parasphenoid outgrowth found in Cottus. Across the
dorsal surface of this process of th e proôtic, or between it and th e column th a t bounds the anterior
edge of the facialis opening, this depending on the shape of th e process, the truncus trigeminus has
its exit from th é chamber.
The mesial wall of the trigemino-facialis chamber is perforated by three or four foramina;
two of them being large and th e o ther one or two considerably smaller. Where there are four foramina,
one of th e large ones transmits the root of th e trigeminus together w ith th e buccalis lateralis, the other
large one transmitting th e motor root of th e facialis together with th e lateralis facialis and all of the
communis fibers of th e trigemino-facialis complex; th e two small foramina transmitting, one, the
ophthalmicus lateralis and the other the ciliaris profundi with th e encephalic vein. Where there are
b u t three foramina, th e ophthalmicus lateralis issues with the trigeminus and buccalis lateralis through
a p a rtly separate portion of a single large foramen, the profundus and facialis always issuing through
independent foramina. The p alatinus facialis issues through the facialis foramen, then turns mesially
along th e floor of th e trigemino-facialis chamber, and so enters th e myodome. I t is not here enclosed
in a separate canal. Directly mesial to th e profundus foramen, the p repituitary portion of the mesial
process of the proôtic is perforated by the oculomotorius, th a t nerve in 5 cm and 6 cm specimens of
Lepidotrigla, separating into its superior and inferior divisions before reaching its foramen. The
postpituitary portion of th e mesial process is, in large specimens, either perforated or notched by a
foramen th a t transmits th e abducens, th a t nerve passing directly from the cranial cavity into the
myodome.
In the ventral edge of the proôtic, is the internal carotid incisure. Posterior to th a t incisure
the ventral edge of the bone is capped its full length with cartilage and abuts against the parasphenoid
in the deep groove along the lateral surface of the median longitudinal ridge on the dorsal surface
of the bone.
On the internal surface of the proôtic there is, as in Scorpaena, a trigemino-facialis recess, and
this recess lodges, as in Scorpaena, the communis, lateralis and profundus ganglia.
On the lateral surface of the dorsal portion of the proôtic there is a fossa, and immediately
anterior to the fossa a brace-like process, the process and fossa^giving insertion to the two internal
and firs t four external levators' of the branchial arches, as in Sòorpàena. Between the thick dorsal
end of this brace-like process and th e adjoining portion of the sphenotic, there is a deep socket-like
articular fàcet for the anterior articular head Of th e hyomandibular. Slightly posterior to this facet,
bn th e lateral surface of th e pterotic, is the oval and shallower facet for th e posterior articular head
of fhe Hyomandibular. Immediately dorsal to th e line between these two articular facets, there is
a 1 pit-like depression on the adjoining edges of the pterotic and sphenotic, -the depression lying immediately
beneath the póstfrontal. I t is th e dilatator fossa, the dilatator operculi arising pa rtly in this
fossa and p a rtly on th e external surface of th e dorsal end of th e hyomandibular, as- in Scorpaénà.
Immediately anterior to th e dilatator fossa, and. slightly dorsal to th e anterior articular facet for the
hyomandibular, on th e slightly còncave dorso-lateral corner of the sphenotic, the levator arcus palatini
has its Origin. A canal for th e ramus oticus traverses th e sphenotic, entering th a t bone On its
o rbital surface.
At about the middle of th e lateral surface of the brain case, and near the hind edge of the
proòtic, th e re is a small foramen which transmits the root of the nervus glossopharyngeus. Dorsal
to th e line between this foramen and the vagus foramen there is a triangular subtemporal depression
which, as in Scorpaena, gives origin to the adductor hyomandibularis and adductor operculi, and also,
immediately posterior to th e la tte r muscle, to th e external levators of the fourth and fifth branchial
arches. The levator operculi has its origin along the dorsal edge of th e lateral surface of the skull,
as in Scorpaena.
The PTEROTIC contains two latero-sensory organs innervated by the oticus lateralis, and
one post-preopercular organ innervated by th e supratemporal branch of th e lineae lateralis vagi.
The two organs innervated by th e oticus were found in both of the two specimens examined, one being
an adult Trigla and th e other a small Lepidotrigla. These two organs lie relatively close together
and there is no indication w hatever of a p rimary tube between them. They accordingly quite probably
represent th e two independent otico-squamosal organs of Amia, here, in process of concentration into a
single organ, exactly as already Set forth for the fourth and fifth supraorbital organs of this fish, of
Sebastes and of Scorpaena. Otherwise the pterotic of Trigla offers no apparent difference from the
bone in Scorpaena, excepting in th a t its posterior process is less extensive. The dorsal portion of the
hind edge of th e lateral surface of th e b rain case projects latero-posteriorly as a tall, th in ridge of bone,
b u t this ridge is formed mainly b y portions of the exoccipital and opisthotic, its dorsal edge only being
formed by th e posterior process of the pterotic. . • ...
The OPISTHOTIC forms an actual p a rt of the bounding wall of the posterior semicircular
canal, A p a rt of th a t p a rt of th e pterotic region of the chondrocranium th a t, in Scorpaena, bounds
this canal having been suppressed in Trigla, and a large opening, leading directly into the canal, being
exposed when the opisthotic is removed. The opisthotic does not, however, seem to have anywhere
acquired primary relations to the skull, the underlying cartilage-., Apparently having simply been
resorbed.
The EXOCCIPITAL-ds perforated b y two foramina, one for the vagus and the other for the
occipital nerves, these two-foramina being separated by the base of th e condylar process th a t gives
articulation to the anterior Articular process of th e first vertebra. In Scorpaena both of these foramina
lie antero-lateral to th e base of the condylar process, ■ separated b y a slight ridge which is a ventral
prolongation of the posteró-lateral Angle, of the skull. Dorsal to the foramen for the occipital nerves