The levator arcus palatini is a strong muscle which arises from the small roughened surface
on the dorso-lateral corner of the sphenotic. Running almost directly downward it spreads forward
and backward, its deeper fibers being immediately inserted on the external surface of the dorso-anterior
portion of the hyomandibular. The more superficial fibers of the muscle are inserted in part on the
dorsal edge of the lateral flange on the hind edge of the metapterygoid, but in larger part they run
downward between th a t flange and the mesial one and have their insertions on the latter flange, in
the membrane th a t extends from th a t flange to thé anterior edge of the .hyomandibular, and also
partly on adjoining portions of the hyomandibular.
The adductor arcus palatini is a broad sheet of muscle th a t has an origin and insertion similar
to th a t of the muscle in Scorpaena. The surface of origin begins posteriorly, on the external surface
of the narrow bridge of bone th a t forms the external wall of the trigemino-facialis chamber, runs
downward onto the ascending process of the parasphenoid and then, turning forward, extends along
the ventro-lateral surface of the parasphènoid nearly to the anterior end of th a t bone. Running
ventro-laterally the fibers of the muscle have their insertion in a long line th a t begins on the inner
surface of the anterior edge of the dorsal portion of the hyomandibular and extends forward along
the dorsal edge of the metapterygoid, and then onto the entopterygoid and the palatine cartilage and
bone, the line of insertion passing along the dorso-mesial edge of the metapterygoid instead of crossing
the internal surface of th a t bone, as it does in Scorpaena. The small entopterygoid lies upon the
internal surface of the ventral edge of the muscle and gives insertion to certain of its fibers.
The adductor hyomandibularis, and the dilatator, adductor and levator operculi have already
been sufficiently referred to when describing the opercular bones.
5. L A T E R O - S E N S O R Y C A N A L S .
The latero-sensory canals of Trigla differ in no essential particular from those of Scorpaena.
As in th a t fish, the primary tubes branch repeatedly after they leave the bones to which they are
related and enter the overlying dermal tissues, large and complex dendritic systems being formed.
The lachrymal lodges three sense organs of the main infraorbital line, the large second infraorbital
bone, four organs, and the third and fourth bones one organ each. This makes nine organs
in all in this part of the line of Trigla, which is two more than is found in Scorpaena, and one more
than is found in Cottus even when counting the small supplemental organ in the second infraorbital
bone of th a t fish.
The postfrontal lodges one sense organ innervated by the oticus lateralis, and the pterotic
two organs innervated by the same nerve. The two organs in the pterotic are without intervening
primary tube, and are probably, as already explained, in process of condensation into a single organ.
The pterotic also lodges a post-preopercular sense organ, innervated by a branch of the suprateni1-'
poralis lateralis vagi, this organ not being found in Scorpaena but being found in Cottus.
The lateral extrascapular, suprascapular and supraclavicular each lodge one organ of the main
line, the organs in the first two bones being innervated by branches of the supratemporalis lateralis
vagij and the organ in the supraclavicular by the next following and single branch of the nervus lineae
lateralis vagi.
The supratemporal canal forms a cross-commissure with its fellow of the opposite side, and
contains two organs, one lying in the lateral extrascapular and the other in the parieto-extrascapülar,
both innervated by branches of the supratemporalis lateralis vagi.
The supraorbital canal contains six sense örgans, one lying in the näsal and five in the frontal.
As in Scorpaena, the fourth primary tube anastomoses in the middle line with its fellow of the
opposite side to form a frontal commissure, the penultimate tube anastomoses with the main infraorbital
canal between the frontal and pterotic bones, and the primary' tube between the fourth and
fifth organs of the line has been suppressed.
The preoperculo-mandibular canal anastomoses a t its dorsal end with the main infraorbital
canal between the pterotic organs th a t are innervated by the oticus lateralis and the supratemporalis
lateralis vagi. I t contains eleven sense organs, four lying in the dentary, one in the articular and six
in the preopercular, as in Scorpaena, this being one more organ in the dentary and one more in the
preopercular than is found in Cottus. The next to the most dorsal organ in the preopercular was nearly
always a double organ.
II. Trigla lyra.
In Trigla lyra the granulations on the dorsal surface of the skull are considerably smaller than
in T. hirundo, and the striae smaller and more numerous. This gives to the surface a sand-paper-like
feel and appearance. The preorbital part of the skull is bent downward somewhat more than in
T. hirundo and the skull is everywhere relatively taller than in th a t fish, excepting only in the anterior
half of the snout, where it has the same relative height. On the posterior half of the dorsal surface
of the snout there is a large, low, median swelling. The interorbital portion of the dorsal surface of
the skull is but slightly concave, and there is, on either side, but one, short and stubby, preorbital
spine. The postorbital portion of the dorsal surface of the skull is decidedly convex in transverse
section, and slightly convex in median longitudinal section; and there is no slightest indication of a
subquadrangular groove.
The rostral depression is relatively larger than in T. hirundo. The nasal rests definitely upon
the summit of the anterior palatine process of the ethmoid cartilage, the rounded antero-ventral
surface of the latter process articulating with a facet a t the base of the maxillary process of the palatine.
The anterior edge of this facet on the palatine is raised to form an eminence which gives insertion
to the rostro-palatine ligament, and this eminence; lying-in front of the palatine process of the ethmoid
cartilage, fits in between the nasal above and the ascending process of the vomer below in such a
manner that it seems to form part of the articular contact of the palatine with this part of the skull.
The lateral edge of the nasal has a sliding articulation with the dorsal surface of the lachrymal, as in
T. hirundo.
The ectethmoids suturate with each other in the middle line behind the mesethmoid, as Gunther
has stated. The orbital surface of the bone includes the orbital surface of the bone in T. hirundo
and also th a t little surface that lies between the two posterior portions of the ridge along the lateral
edge of the ventral surface of the bone in the same fish. This condition thus being intermediate
between th a t in T. hirundo and th a t in Scorpaena.
The median anterior eye-muscle canal, in the antorbital cartilage, so well developed in
T . hirundo, is here represented by what is little more than a perforation of the extreme anterior end of
the interorbital septum. From there a canal for the olfactory nerve runs forward on either side, this
canal being enlarged, as in T.: hirundo, to form a deep and large recess in the hind end of the meseth