2. I N F R A O R B I T A L B O N E S .
The infraorbital-. bones are all marked with granulated surface striae,- and there were, in the
two large specimens,, b u t three of. these bones: In all of the several smaller specimens there were
four bones, the first and secpnd bones of the series, found fused-in theUarger specimens, here being
separate and distinct.' Trigla hirundo thus differs in the number-of; its, infraorbital bones froip. any
of the combinations given by Gunther in his descriptions of the fishes of the family, th a t author giying
five of these-bones in Trigla pini, two in Trigla gurnardus and six in Trigla lyra¿ But these numberjs,
given by. Giintber, may not be correct for all ages of the fishes mentioned,-for in two specimens of
T. gurnardus sent me by Dr. Allen, of Plymouth, England, there were five infraorbital bones instead
of two as stated by.Glinther,
The. anterior bone of the series, in thè smaller specimens of Trigla hirundo, is the lachrymal’,
and is a large and somewhat triangular bone, -the anterior end of which; curves strongly inesially
and so gives to the., bone, a concave, internal and convex external surface. The curved anterior end of
the bone is considerably thickened, but its ventro-anterior edge is simply coarsely serrated and not
furnished with prominent, spines, as Günther states in his descriptions of this fish. In this the fish
resembles Gunther’s.. descriptions of Trigla gurnardus rather than T. hirundo, its colour and, other
characteristics however identifying it as the latter. The thickening of this anterior end of the lachrymal
is apparently due to accretions to its inner surface, and this surface of this part of the bone
is partly covered with surface striae or granulations. From the hind end of this thickened portion,
two ridges run backward on the internal surface of the bone; one along the ventral edge of the bone;
and the other near and parallel to its dorso-anterior edge; both ridges being prolonged beyond the
body of the bone as relatively long and slender processes. The dorso-anterior edge of the bone, dorso-
anterior to the second one of the two ridges just above mentioned, is thin, and its anterior and posterior
thirds rest upon and are firmly bound to portions of the dorsal edge of the palatine. Between these
two regions of contact with the palatine, the lachrymal is cut away by a long oval incisure which
is bridged by the underlying palatine. An opening is thus left between the lachrymal and the palatine,
this opening lying directly opposite the slit-like opening of the nasal pit and lodging the lateral half
of the nasal sac. That part of this edge of the lachrymal th a t lies anterior to this nasal incisure rests
upon the maxillary process of the palatine, and there has a flat, pointed, and more or less developed
process which, as stated when describing the nasal, gives Sliding articulation to the antero-lateral corner
of that bone. That part of the edge of the lachrymal that lies'posterior to the nasal incisure inclines
mesially and rests upon those portions of the palatine bone and cartilage th a t form the posterior ethmoid
process. On the external surface of this part of this edge of the lachrymal there is a small groove,
parallel to the edge and extending posteriorly to the base of the slender ánd related- dorso-posteriof
process of the bone. At its anterior end this groove is bounded mesiáílyTby -a part of the palatine,
and hère, and throughout the larger part of its length, the groove isj in'-large spécimens', filled with
a line of tough fibrous tissue which binds the bone to the summit of the articular'ridge on the ventral
surface of the ectethmoid. There is thus articulation here between' théêe two'structures, but there
are no regular articular surfaces. The articulation, such a s1 it is; represents the combined ethmo-
lachrymal and posterior ethmo-palatine articulations. Posterior to this articular portion, thé dorso-
posterior process of thé lachrymal projects backward as a free and slender process which lies'against
and is closely attached to the largemone. of the two ethmo-palatine ligaments already ¿described. Thisligament,
running forward from its point of origin on the ectethmoid, has its insertion on the palatine
cartilage, the process of the lachrymal thus bèing developed in supporting relation to it. The second
ethmo-palatine ligament is, as already stated, a slender and delicate one th a t arises from the ventral
surface of the ectethmoid. Running forward from thère, parallel to but at a certain distance from
the larger ligament, it also is inserted on the hind end of the palatinè cartilage.
The lachrymal is traversed by the infraorbital latero-sensory canal and lodges three organs
of th a t line.
The second infraorbital bone is a large and almost parallelogrammic bone. The striae on its
o u te r surface radiate mainly from a p oint th a t lies n ear the ventral quarter of the bone directly superficial
to th e latero-sensory canal th a t traverses the bone, b u t pa rtly also from a second point th a t
lies slightly antero-ventral to the first -one- and also directly superficial to a portion of the latero-
sensory canal; these two points apparently representing the centers of ossification of- two bones,
here fused b u t found separate in a 63 mm specimen of Lepidotrigla examined in serial sections.1)
In the hind edge of thé bone, a t about its ventral third, there is a more or less pronounced
angular incisure. Dorsal to’ this’ incisure the hind edge of the bone abuts against the anterior edge
of the preopercular, overlapping it but slightly a t any place. Ventral to the incisure, the bone also
abuts against the anterior édge of the preopercular, but it there also rests upon the. lateral edge of
the posterior process’of the quadrate, the attachment to this latter bone being particularly strong,
miich stronger than to the preopercular. The point' of the incisure lies in the line, anteriorly produced,
of the dorsal and largest preopercular spine, and fits against a pointed portion, of the anterior surface
of the outer edge of the preopercular. From the point of the incisure, and extending backward across
the outer surface of the preopercular to the base of its dorsal spine, there is a slight but distinctly
evident tuberculated ridge, this ridge being also continued forward across the second infraorbital
bone. Ventral to the ridge, both the preopercular and second infraorbital incline slightly downward
and inward, the ridge thus separating two somewhat inclined surfacès. In my large specimens this
ridge is but- slightly indicated, while in the small ones it is quite pronounced.
• The infraorbital latero-sensory canal enters the second infraorbital bone on its outer surface
near the middle point of its dorsal edge, this point lying at the anterior edge of the orbit. Posterior
to this point there is a depressed region on the outer surface of the dorsal edge of the bone, the depression
lodging the ventral portions of the third and fourth infraorbital bones. From the point
where the canal enters the outer surface of the second infraorbital bone it runs downward and for-,
ward in the line of the striae on the outer surface of the bone until it reaches the principal point from
which those striae radiate. There it sends a long primary tube backward nearly to the hind edge of
the bone, and itself turns gradually forward to leave.the bone a t its anterior end and enter the
lachrymal. The, primary tubes [that arise from the canal as it traverses the bone all open on its outer
surface ventral tô thé longitudinal striated ridge just above described.. The bone lodges four organs
of the infraorbital line.
The third and fourth infraorbital , bones are relatively small. The third bone has the shape
of an elongated rectangle, occupies the larger part of the depressed region along the dorsal edge of
the second infraorbital bone, and forms the ventral edge of the orbit. The fourth bone is. somewhat
i) Since thè completion of the manuscript these two bones have also been found separate in a medium-sized specimen
of Trigla hirundo.
Zoologica. H e f t 57. 17