The ECTETHMOID has dermo-perichondrial and primary portions, and resembles, in general
shape, th e corresponding bone in Trigla. Its posterior surface forms th e anterior wall of th e orbit.
Posteriorly, its superficial component suturâtes with th e frontal, while mesially it suturâtes with
th e mesethmoid and nasal, extending forward, along th e lateral edge of th e la tte r bone, almost and
sometimes quite to the hind edge of a small .oval nasal incisure in th e lateral edge of th e skull. This
anterior end of th e ectethmoid, when it reaches the nasal incisure, forms only a point in the hind
wall of th a t incisure, and th e bone has no other bounding relations to th e nasal pit. The mesial edge
of th a t p a rt of th e ectethmoid th a t bounds th e nasal bone is grooved, and th e lateral edge of the
related portion of th e nasal bone, th a t edge of the nasal bone here being grooved on its dorsal surface,
fits into th e groove on the ectethmoid; th e nasal bone thus appearing, in dorsal views, to here
underlie th e ectethmoid, while in reality it overlies it. Between th e dorsal edge of this portion of the
ectethmoid and th e dorsal surface of th e body of th e nasal, there is th e long and wide groove above
referred to, which groove, although it appears to lie between th e two bones, lies largely on th e dorsal
surface of th e nasal bone alone. This groove is roofed, in th e recent state, by a th in and tightly
stretched drum-head-like membrane, which is pierced b y several small holes, th e groove lodging
he anteriorly-directed second supraorbital primary tube, and the several small holes being the pores
by which th a t tube opens onto th e outer surface. Similar drum-head-like membranes, perforated by
several small holes, are found associated with nearly all of the primary latero-sensory tubes on the
head of the fish, b u t none of them are so large as this second supraorbital one.
The ventro-lateral edge of th e ectethmoid presents three regions, one of which forms the
anterior half of th e edge, and the other two its posterior half. The edge of the bone in th e posterior
one of these three regions is presented ventrally, in a line th a t extends posteriorly and slightly
laterally, an d forms the ventral edge of th e lateral portion of th e orbital surface of th e bone. On
th e outer surface of this p a rt of the bone there is a smooth surface which gives a sliding articulation
to a corresponding surface on the inner surface of th e dorsal edge of the third infraorbital bone. Immediately
anterior to this posterior portion of th e ventro-lateral edge of th e bone, there is a short portion
which is thickenëd and rounded to form an articular edge which articulates with a groove on the
dorsal edge of w hat I shall later describe as th e dermo-ectopterygoid. Directly mesial to this articular
edge, a groove begins on th é ventral surface of the ectethmoid and continues forward along the
v entral surface of the lateral edge of th e anterior half of the bone. The anterior portion of th e lateral
edge of the bone, lateral to the groove, is rounded. When the cheek bones swing inward the groove
receives the dorsal edges of th e palatine and dermo-ectopterygoid, and limits th e swing of th e bones.
When the cheek bones swing outward th e rounded lateral edge of th e ectethmoid enters a groove
on th e dorsal edge of th e lachrymal, between it and th e palatine, and limits th e swing of the bones
in th a t direction.
A small olfactory canal perforates th e antorbital cartilage, mesial to th e ectethmoid, lying,
in its posterior portion, in th e specimens examined, wholly in th a t cartilage.
The VOMER caps the end of the th in flat and broad cartilage of the snout, and is wholly
without, teeth. I t has à broad th in and delicate body, which lies pa rtly on th e v entral surface of the
cartilage of the snout and p a rtly on th e ventral surface of th e parasphenoid, and two short wide
and somewhat stouter ascending processes which lie on th e dorsal surface of th e cartilage of the
snout and come into contact, posteriorly, with the anterior edges of the ventral plates of the nasals.
There is a broad rounded incisure between the two ascending processes, the incisure embracing the
anterior end of a small median interspace of cartilage which lies between this incisure and a median
incisure between the adjoining anterior edges of the ventral plates of the nasals. Directly anterior
to th e incisure in the vomer, there is a very small median eminence on the anterior edge of. the bone,
and midway between this eminence and the lateral edge of the bone there is a larger eminence, also
on the anterior edge of the bone. Running dorso-laterally from this la tte r eminence there is a slight
ridge which terminates in an eminence on the dorsal surface of the ascending process of th e bone.
Lateral to this ridge and eminence there is a broad and shallow groove which gives articulation, through
th e intermediation of a pad of tough fibrous tissue, to the postero-mesial surface of the ascending
process of the maxillary. Lateral to this articular groove, the ascending process of th e vomer bounds
and supports th e anterior palatine process of the ethmoid cartilage.
The ROSTRAL is pyramidal in shape, as in Trigla, and gives support, on its anterior surface,
to th e ascending processes of th e premaxillaries. Its internal surface rests upon the little median
interspace of cartilage on th e dorsal surface of the snout, and also on the adjoining portions of the
ascending processes of th e vomer. This interspace of cartilage lies considerably anterior to the nasal
pits, as it does in Trigla, instead of being internasal in position, as it is in Scorpaena.
Whether there is in Peristedion, as in Trigla, a diverticulum of th e nasal sac of either side
th a t extends into the rostral depression, was n o t investigated; b u t it would seem not, the space
beneath th e anterior end of th e nasal seeming too small to permit it.
The PREMAXILLARY is a slender untoothed bone, with a large flat and th in postmaxil-
lary process, and small ascending and articular processes. The proximal end of th e shank of the
bone is bent so as to project postero-ventrally and slightly mesially, and from th e base of this bent
portion th e short ascending process arises; this process and th e proximal end of the bone together
forming a straight edge, and together looking like the flattened and broadened proximal end of the
bone. This straight edge of th e bone lies close to its fellow of the opposite side, th e ascending process
being directed dorso-anteriorly instead of dorso-posteriorly. From the dorso-anterior end of the
process, or from th e rostral immediately posterior to it, a ligament arises, and running ventro-postero-
laterally is inserted on the maxillary a t the base of the ascending process of th a t bone. This ligament
is apparently the homologue of one half of the rostro-palatine ligament of Scorpaena and Trigla,
th e other half of th e ligament arising on the maxillary, close to the point of insertion of this one,
and extending from th a t bone to th e palatine. The articular process of the premaxillary is small,
is directed dorso-posteriorly, and articulates with a large b u t low articular eminence on the anterior
surface of the proximal end of the maxillary.
The MAXILLARY has a slender shank, with its distal end abruptly expanded. On the anterior
surface of the proximal end of th e bone there is a large oval eminence which gives articulation to
th e premaxillary, the long axis of the eminence being directed dorso-distally across the anterior
surface of the bone. From th e dorsal edge of th e bone, in the line of the axis of the articular eminence,
th e ascending process of th e bone arises, th e process lying transverse to the shank of the bone and
being directed dorso-postero-laterally. The postero-ventral edge of the process is thickened, and
has a sliding articulation with th e dorsal surface of the ascending process of th e vomer, in the groove
already described, the articulating surfaces being separated by a pad of tough fibrous tissue. In the
angle between th e distal surface of the process* and the shank of the bone, is the articular surface for