On either side of this median rod of cartilage, th e dorsal surface of th e vomer forms th e floor of the
anterior h alf of the rostral chamber. Posterior to the vomer, th e antorbital cartilage expands rapidly,
on either side, and th en again contracts to a narrow median column which is continuous dorsally
with th e ventral surface of th e anterior end of a broad band of cartilage which forms th e roof of the
interorbital, olfactory prolongation of th e cranial cavity. A diamond-shaped or nearly square surface
of cartilage thus forms th e median portion of the post-vomerine portion of the floor of the rostral
chamber, this cartilage being bounded laterally, on either side, by the pedicle of th e ectethmoid.
There is th u s no bone whatever a t any point in th e median line of th e floor of th e chamber.
The hind wall of the rostral chamber is formed by th e median column of cartilage ju s t above
referred to, and, dorsal to th a t column, by the broad anterior end of th e roofing band of interorbital
cartilage. This anterior end of this la tte r cartilage projects forward slightly beyond th e median
column, slightly overhangs th e hind end of th e rostral chamber, and gives support, on its dorsal
surface, to th e hind end of the so-called median ethmoid. Immediately beneath this p a rt of the
median ethmoid there is, on either side, a slight eminence on the anterior edge of the cartilage, each
eminence giving origin to a ligament which runs antero-ventrally and is inserted on the dorsal surface
of the maxillary immediately lateral to its ascending process. This ligament is thus the homologue
of the ethmo-maxillary ligament of the other fishes of th e group, and th e little eminence of cartilage
from which it has its origin must accordingly be the mesethmoid process; b u t it is a process of th e
ethmoid cartilage only, there being no primary bone whatever in any immediate relation to it. On
a slight m edian ridge in th e cartilaginous floor of th e chamber, th e v entral surface of the rostral glides.
There is accordingly, in this fish, no mesethmoid bone. Tha t th e median portion' of the ethmoid
cartilage should remain unossified, and th a t a median ethmoid bone, of primary origin, should
nevertheless be found wholly external to th a t cartilage, dorsal to the rostral instead of ventral to it,
and dorsal even to th e mesethmoid processes of th e ethmoid cartilage, is evidently impossible.
The roof of the rostral chamber is formed by the single median so-called ethmoid or prosethmoid.
This bone suturates posteriorly with the frontals. Laterally, on either side, it saturates,
in its posterior half, with the ectethmoid, while in its anterior half it forms th e mesial boundary of an
elongated nasal opening; which opening lies between this so-called ethmoid and th e anterior portion
of th e ectethmoid, opens directly into th e nasal p it and encloses th e two nasal apertures. At the
anterior end of th e opening, th e two bounding bones closely approach each other, b u t do n o t quite
come into contact, a narrow space being left between them, closed antero-ventrally by th e lachrymal.
Slightly antero-mesial to th e nasal opening, there is, on th e anterior edge of th e so-called
ethmoid, a short, broad, s tout process which projects ventrally and antero-laterally. This process
arises from th e deeper layers only of th e bone, the anterior edge of th a t superficial portion of the
bone th a t bears the surface m arkings continuing, uninterruptedly, external to it. The internal surface
of the process forms a large flat articular surface which gives a sliding articulation to the flattened
anterior end of th e m axillary process of th e palatine. On its external surface the process gives support
to th e internal surface of the dorsal edge of th e lachrymal, the two bones being strongly b u t somewhat
loosely bound together by fibrous tissue, a slight sliding and oscillating motion, combined, of th e
lachrymal being permitted. The process thus corresponds, in its relations to the palatine and lachrymal
bones, to th e process-like antero-lateral corner of the nasal bones of Trigla and Peristedion,
excepting th a t here, in Dactylopterus, it is developed as a process-like prolongation of the ventral
layers of th e bone, and is interposed between th e palatine and lachrymal instead of lying on the
dorsal surfaces of those two bones. The process may accordingly be called the lachrymo-palatine
process of the bone. From its postero-lateral edge, on the internal surface of the body of the bone,
a tall sharp ridge begins, and running postero-mesially, nearly to the hind end of the bone, marks the
boundary between th e dorsal portions of the rostral chamber and the nasal p it; those two chambers
being confluent beneath the ridge. Between the hind ends of the ridges of opposite sides there is,
on the internal surface of th e bone, a deep median p it which nearly perforates the bone and lodges
th e distal ends of th e ascending processes of th e premaxillaries. Immediately postero-lateral to the
lachrymo-palatine process, close to th e narrow space th a t leads into th e nasal opening, the supraorbital
latero-sensory canal begins, and running a t first dorso-mesially and then curving posteriorly,
traverses the bone and issues a t its hind edge, there entering the frontal. This median so-called
ethmoid or prosethmoid bone of Dactylopterus is thus certainly a bone formed by the fusion, in the
median line, of th e two nasal bones of th e fish.
The ROSTRAL is a narrow, flat and ta ll cartilage, which lies between the hind ends of the
articular processes of the premaxillaries, and gives support, on its dorsal edge, to the ascending
processes of those same bones. Its ventral edge has a slight median groove, and this groove slides
upon a slight median ridge on th e cartilaginous floor of the rostral chamber. The rostral is relatively
small, as are also the maxillary and premaxillary bones; and all of these elements of the upper jaw
of the fish are entirely concealed, in dorsal and lateral views, beneath th e nasal and lachrymal bones.
The PREMAXILLARY has a long, flat and pointed ascending process, a relatively long,
large and flat articular process, and a short and flat horizontal portion, or body. The short body
of the bone ends in a broad blunt end, and its flat oral surface is garnished its full length, or very
nearly so, with small villiform teeth. The ascending process arises by a broad base from the mesial
{proximal) end of the body of th e bone, and, in the medium-sized specimens, is directed dorsally
and b u t slightly backward. I t lies in a nearly longitudinal plane, inclining and b u t slightly ventro-
mesially, th e flat surfaces of the processes of opposite sides enclosing between them a deep and
narrow groove. The long flat articular process also lies in a nearly longitudinal plane, inclined a t a
slight angle to th e ascending process, th e two processes projecting dorso-posteriorly nearly parallel
to each other and separated by a narrow intervening space. From the distal surface of the base
of the ascending process a rod of tough gristly tissue arises, and extending distally along the dorsal
surface of the body of the bone, is attached, a t its distal end, to the distal end of the maxillary.
This rod of gristly tissue lies in the upper labial, or maxillary dermal fold, thus occupying a position
th a t corresponds to th a t occupied by a considerable p a rt of the body of th e premaxillary in the other
fishes of the group, the actual body of the premaxillary of Dactylopterus corresponding, not to
th e premaxillaries of th e other mail-cheeked fishes, but. approximately, to the premaxillaries of
those fishes in which the maxillary is said by Sagemehl to lie lateral (distal) to the premaxillary.
The MAXILLARY has a relatively large, right-angled ascending process, similar to th a t
of Scorpaena, and a short broad ligamentary process which corresponds to the proximal half only
of the process of Scorpaena. The distal end of the short and slender body of th e bone is slightly
expanded, gives attachment to th e hind end of the upper labial rod of gristly tissue, and lies in a
marked depression on the outer surface of the mandible. The bone articulates with the premaxillary
and vomer in the same way th a t it does in Scorpaena, and it gives articulation, on the dorsal surface
of its ligamentary process and the adjacent portions of its body and ascending process, to the anterior