The rod-like SYMPLECTIG lies in th e symplectic groove on the internal surface of th e quadrate.
Between it, and th e preopercular and the posterior process, of th e quadrate there is a large
oval opening which transmits the mandibularis externus facialis and th e a rteria hyoidea. Anterior
to th e symplectic, between it and the quadrate, there is a small canal which transmits th e mandibularis
intemus facialis.
The a rteria hyoidea has a course exactly similar to th a t in th e fishes already described.
The PREOPERCULAR has slightly indicated dorsal and ventral limbs, separated by a low
and granulated ridge on th e outer surface of th e bone. This granulated ridge is much more apparent
in small th a n in large specimens, and terminates posteriorly in a spine which, in small specimens, is
sharply pointed. Immediately ventral to this spine there is, in these small specimens, a smaller spine.
The dorsal limb of th e bone is firmly bound to th e hyomandibular, th e ventral limb being similarly
bound to th e posterior process of the quadrate. The anterior edge of th e bone gives support and is
bound to the hind edge of th e second bone of th e infraorbital series. The bone is traversed its lull
length by the preopercular latero-sensory canal, and lodges six organs of th e line, th e second organ
from th e dorsal end of the bone being a double one in th e one specimen examined.
The OPE RCULAR has a large bluntly pointed process which rises from the dorsal edge of the bone
immediately dorsal to the articular facet for th e hyomandibular, and, projecting dorsally or dorso-
anteriorly, nearly reaches the dorso-lateral edge of th e skull in the suprascapular region. The inner
surface of the process is slightly concave and gives insertion to th e adductor operculi,. th a t muscle
having a large surface of origin in the subtemporal depression on the lateral surface of th e skull, the
surface of origin of this muscle lying immediately posterior to th a t of th e adductor hyomandibularis.
Immediately posterior to the base of th e process, on the inner surface of the dorsal edge of th e opercular,
the levator operculi has its insertion; this muscle arising from th e dorsal margin of the lateral
surface of th e pterotic in a line beginning immediately posterior to the latero-sensory tube th a t
anastomoses with th e dorsal end of th e preopercular canal. The dilatator operculi arises p a rtly in
th e dilatator fossa and pa rtly on the external surface of the dorsal end of the hyomandibular, and is
inserted on th e anterior edge of the articular facet for the hyomandibular. On th e hind edge of the
opercular there are two s tout spines, th e dorsal one curving upward so th a t its point is directed almost
dorsally.
The SUBOPE RCULAR is a long, th in and delicate bone. In one of my large specimens th e ventral
half of this bone was wanting, and th e dorsal half was almost completely ankylosed with the hind
edge of th e opercular.
The INTE ROPE RCULAR is bound by strong ligamentous tissue, a t about the middle of its
dorso-anterior edge, to th e interhyal and ceratohyal. Its antero-ventral end is bound, by a short
strong ligament, to th e hind end of the mandible.
The MANDIBLE is relatively longer and more slender th a n th a t of Scorpaena. The hind
edge of the dentarv is Y-shaped and receives, in th e angle of the V, th e long pointed anterior end of
th e articular, overlapping th a t bone externally. The dorsal arm of the Y reaches th e summit of the
coronoid process of th e articular, and is bound to its internal surface, slightly below th e summit
of th e process. Between this arm of the dentary and the adjoining parts of th e articular there is a
relatively small and narrow space. The dorsal edge of th e dentary is broad and is covered with small
villiform te e th ; and immediately ventral to this toothed surface there is a deep longitudinal groove
which lodges, as in Scorpaena, a gristly tapering rod-like structure which forms th e core of the mandibular
labial fold of the fish. The pointed anterior limb of the articular is strongly convex externally
and concave internally, and lodges, in its concave internal surface, the rod-like Meckel’s cartilage.
Posterior to the hind end of Meckel’s cartilage the conformation of th e rod is continued a short
distance b y a rounded ridge of bone. There is a short, stout, sharply-pointed coronoid process. The
hind edge of the articular facet for the quadrate projects dorso-posteriorly as a stout process which
has a sliding articulation on the ventro-posterior surface of the posterior process of the quadrate,
as in Scorpaena. The angular is a small b it of bone th a t caps th e hind end of the articular and gives
insertion to th e strong mandibulo-interopercular ligament. The articular and dentary are both
traversed by the mandibular latero-sensory canal, and lodge, respectively, one and four organs of
th e line.
4. M U S C L E S .
The adductor mandibulae muscle of Trigla has anterior and posterior divisions, instead of, as
in Scorpaena, superficial and deeper ones. The anterior division forms the anterior third or quarter
of the entire muscle and has its origin from a tendinous band th a t extends along its own dorsal edge
and then backward along the dorsal edge of th e posterior division of th e muscle, to have its origin
on the tendinous tissue th a t forms the anterior edge of th e levator arcus palatini. This anterior
division of the adductor has its insertion w holly on a tendinous fascia th a t forms on its internal surface
and th a t terminates anteriorly in two tendons; a stout tendon inserted on the hind end of th e liga-
mentary process of the maxillary, and a less important one inserted on the dorsal surface- of the
same bone.
The large posterior division of the adductor, is pa rtly separated into two portions by th e ramus
mandibularis trigemini, th a t nerve traversing the muscle from its inner surface and issuing on its
outer surface close to its ventral edge. That p a rt of the muscle th a t lies anterior to the nerve has its
origin on th e tendinous band th a t extends along the dorsal edge of the entire muscle, and th a t gives
origin also to the anterior division of th e muscle. I t is inserted in p a rt on the tissues th a t extend
from the p alato-quadrate apparatus to the maxillary, p a rtly on a tendon th a t joins the tendon A2A3,
described below, an d p a rtly on a tendon th a t runs forward and has its insertion on th e dorsal surface
of the maxillary. This p a rt of this division of the muscle, and th e anterior division of th e entire
muscle, thus together correspond approximately to th e superficial portion, A v of the muscle of Scor-
paena. Tha t p a rt of the muscle of Trigla th a t lies posterior to the mandibularis trigeminus then
corresponds to the muscle A2 A3 of Scorpaena, and, like th a t muscle, it arises from the hyomandibular,
th e preopercular and th e outer surface of th e p alato-quadrate arch, and has its insertion on a tendon
th a t may be , called tendon A2A3. This tendon is double, having anterior and posterior portions.
The anterior portion separates into two parts one of which is continuous with a fascia th a t forms on
th e inner surface of Aw, th e other having its insertion on th e internal surface of the articular ventral
to the hind end of Meckel’s cartilage. The posterior portion of th e tendon A2A3 runs downward
along the hind edge of Aw and has its insertion on the inner surface of the articular dorsal to the hind
end of Meckel’s cartilage. There is, in Trigla, no. tendon running backward, as in Scorpaena, from
th e tendon A2A3 to the inner surface of th e quadrate.
The maxillo-mandibular ligament is as in Scorpaena.