The term „posterior“ , used by Sagemehl to describe tb e relations of the maxillary to th e pre-
maxillary, is confusing; for while th e articular end. of th e maxillary certainly lies posterior (internal)
to the premaxillary, the shank of th e bone, in all th e fishes of which I have specimens, lies dorso-
external (th a t is, anterior or lateral, as th e case may be) to th e shank of th e premaxillary, this relation
of the bones being particularly m arked w hen th e shank of th e premaxillary has a certain dorsal process
which I shall describe as th e post-maxillary process of th a t bone.
The dorsal limb of th e vonier of teleosts forms an anterior portion of th e m ore or less developed
internasal wall, and it is of membrane, or perhaps p a rtly of perichondrial origin. I t accordingly does
no t present th e only two conditions th a t I formerly (’98, p. 458) found unfavourable to th e homo-
logization of th e preethmoid (septomaxillary) of Ami a with th e vomer bone of mammals.
P A R A S P H E N O I D .
The parasphenoid of Scorpaena is a nearly straight bone, with well developed ascending processes
near th e middle of its length. I t has a rounded anterior, and a bifurcated posterior end, and
th e anterior portion of its ventral surface is grooved, as usual, to receive th e posterior portion of th e
body of th e vomer. Anterior to its ascending process there is, on th e dorsal surface of th e bone, a
th in longitudinal median ridge which fits into a corresponding depression on tb e ventral surface of
th e chondrocranium. Beginning immediately posterior to th e ascending processes, there is also, on
th e dorsal surface of th e bone, a median longitudinal ridge, b u t this ridge is broad and is grooved on
its dorsal surface. Anteriorly this groove is shallow, b u t posteriorly i t deepens gradually, until, near
th e hind end of th e bone, it cuts through it, leaving only two pointed processes, one on either side.
The groove forms th e median p a rt of th e floor of the myodome (eye-muscle canal), th e ridge lying be tween
th e ventral ends of th e prootics, and th e cartilage th a t caps those bones abutting, on either side,
against its lateral surface.
Swinnerton says (’02, p. 532) th a t, in Gasterosteus, th e ascending process of th e parasphenoid,
on either side, lies anterior to the exit of th e trigeminus nerve, and th a t it meets and overlaps a process
of th e frontal sent down immediately in front of th e sphenotic. Because of this position, anterior to
th e trigeminus foramen, he concludes th a t th e process in Gasterosteus can not be th e homologue of
th e similarly named process in Amia, in which fish i t lies posterior to th e trigeminus foramen. This
conclusion is p a rtly correct and pa rtly incorrect, for th e bases of th e ascending processes, in th e two
fishes, are homologous, while th e dorsal prolongations of those basal portions are not. The entire
process lies, in Scorpaena and Scomber, ventral to th e trigeminus foramen, and this would seem to
be the usual teleostean relation. In Amia, a dorsal prolongation of this basal portion of the process
passes posterior to th e trigeminus foramen, comes into contact with th e sphenotic, and seems to be
in some way related to th e spiracular canal. In Gasterosteus, a dorsal prolongation of th e basal
portion passes upward anterior to th e trigeminus foramen, there invading and taking possession of
th e region occupied, in Amia, by th e so-called pedicle of th e alisphenoid, which la tte r bone is said
by Swinnerton to be absent in Gasterosteus. This arrangement of th e parasphenoid, in Gasterosteus,
is apparently exactly similar to th a t found in Cottus, where th e process of th e bone comes in contact
with th e alisphenoid as well as with th e ventral flange of th e frontal, as will be fully described when
describing th a t fish. Here it need only be said th a t th a t p a rt of th e alisphenoid of Amia th a t has
been described as th e pedicle of th e bone, is largely or even wholly absent in certain teleosts, there
being replaced by membrane, which membrane might easily be invaded by outgrowths from a neighbouring
membrane bone.
In Gonorhynchus Grevi there is, according to Ridewood (’05 b), a process th a t would seem to
be similar to th a t of Gasterosteus and Cottus, b u t somewhat more developed, for it is said to come
in to contact with the sphenotic (postfrontal, Ridewood) as well as with the alisphenoid.
In Osteoglossum formosum, Bridge (’95) describes two processes on the parasphenoid, one of
which would seem to be exactly similar to th a t of Gonorhynchus; for, although its relations to the
trigeminus foramen are not given, it is said to come into contact with both the sphenotic and alisphenoid.
Bridge considers this process of Osteoglossum as th e equivalent of th e processes of Amia,
Acipenser and Polypterus; b u t if, as seems so evident, it is simply an exaggerated development of
th e processes of Gasterosteus and Cottus, it can not be th e equivalent of th e process of Amia. I t is
also not th e homologue of th e process of Polypterus, as is shown immediately below. Whether it is
the homologue of th e process of Acipenser, or not, I can not determine from th e descriptions and
figures th a t I find of th a t fish.
The second process of th e parasphenoid of Osteoglossum is said b y Bridge to grow out of the
lateral edge of th a t bone immediately ventral to the root of th e ascending process. I t projects laterally
and slightly upward, and gives articulation to an a rticular surface on th e dorsal edge of the metapterygoid.
I t is said to have no parallel in any other teleostean fish, b u t to be represented in Lepidosteus
by what is an essentially similar process. This process in Lepidosteus is fully described in th e chapter
of this work devoted to th e myodome, and th a t it is the homologue of the process of Osteoglossum
seems to me, from th e figures of this la tte r fish, very doubtful.
In Polypterus, according to Traquair (’70), th e ascending process of th e parasphenoid has not
only a horizontal portion, or process, which may perhaps be th e homologue of the horizontal process
of Osteoglossum, b u t also two dorsal prolongations. One of these dorsal prolongations is apparently
the homologue of the sphenotic prolongation of the process of Amia, the other being still a third
prolongation, n o t described in any other fish, which projects dorso-posteriorly, embraces the facialis
foramen, and comes into contact with th e so-called opisthotic bone.
P R E M A X I L L A R Y .
The premaxillary consists of a curved body, often called the horizontal p a rt of th e bone, and
th re e processes which rise perpendicularly to th a t body. The curved body of th e bone ends in a blunt
point, and its oral surface is covered, nearly its full length, with small villifornr teeth, while on its
dorsal surface, and extending its full length, there is a slight groove. The three processes of the bone
rise from the ental edge of this groove, and th e groove lodges th e ventral edge of the maxillary.
One of th e three processes of the premaxillary is a th in triangular flange th a t rises, longitudinally,
from th e distal half of the body of th e bone. I t projects upward and postero-mesially, perpendicularly
to the body of the bone, lies against the internal surface of the maxillary, and, because
of this position, may be called the postmaxillary process of the premaxillary. In certain teleosts
this process forms the hind end of the premaxillary, th e more distal portion of th e bone of Scorpaena
being represented, in such fishes, by tough gristly connective tissue. This would seem to indicate
th a t the premaxillary primarily extended only to this process, and it would also seem to in