dicate th a t the bone of Scorpaena, up to and including this process, is the equivalent of th e entire
premaxillary in those fishes in which th e maxillary lies, in Sagemehl’s terminology, lateral to th e
premaxillary. This, however, requires investigation.
The other two processes of th e premaxillary both arise from the proximal end of th e b'oner
and, in th e descriptions of many fishes, are both included under th e term ascending process. B ut
one of them only is properly th a t process, th e other being a greatly developed articular process..
The ascending process, properly so-called, is directed dorso-posteriorly, and is a long, thin,,
pointed, plate-like piece of bone which lies in a plane th a t crosses obliquely and perpendicularly
th e extreme proximal end of th e premaxillary. Its internal surface is presented ventro-postero-
laterally and its mesial and larger p a rt rests upon and is firmly attached by connective tissue to the
corresponding half of th e grooved dorsal surface of th e cartilaginous rostral, its mesial edge touching,
throughout nearly its entire length, in th e mid-dorsal line, th e corresponding edge of its fellow of
the opposite side. The external surface of the process is presented antero-dorso-mesially, and so
forms, with its fellow of th e opposite side, a Y-shaped longitudinal groove on th e dorsal surface of
the anterior end of th e snout. This groove is wide antero-ventrally, b u t tapers dorso-posteriorly
to a narrow end. The antero-ventral end of th e groove is filled with a pad of tough fibrous tissue
which extends downward between th e anterior ends of the two premaxillaries and binds them strongly
b u t loosely together. The dorso-posterior end of the groove lodges a similar b u t smaller pad of tissue,
and this pad gives attachment to a s tout ligamentous band which here crosses th e outer surface of
th e two ascending processes. This ligament, from here, runs downward and laterally, on either side,
passes ventral to th e nasal bone, between i t and th e ethmo-maxillary ligament, and is inserted on
the base of the maxillary process of the palatine. A branch of this ligament runs antero-ventro-
laterally to th e antero-mesial corner of the articular process of th e premaxillary and then laterally
to th e mesial (proximal) end of th e ligamentary process of th e maxillary, having an attachment a t
each of these points; while a smaller branch of th e ligament runs backward and laterally, and is
inserted on th e anterior surface of th e mesethmoid process. The function of this la tte r branch of the
ligament is evidently simply to fix a limit to th a t anterior motion of the rostral th a t accompanies
th e protrusion of the premaxillaries, th e main ligament holding th e rostral down upon th e dorsal
surface of th e snout.
The articular process of th e premaxillary arises from th e bone immediately lateral (distal)
to the ascending process. I t is a relatively large plate of bone which lies in a plane th a t begins a t
th e antero-lateral edge of th e base of th e ascending process, a t an acute angle to the plane of th a t
process, and from there runs postero-laterally across th e dorsal surface of th e body of th e bone. At
th e point where its antero-mesial edge joins th e antero-lateral edge of th e ascending process, there
is a marked b u t rounded angle in th e antero-lateral edge of th e la tte r process. The external surface
of th e articular process is flat and smooth. On th e postero-lateral portion of its internal surface
there is a large flat articular eminence which gives articulation to a p a rt of th e articular head of th e
maxillary, in a manner th a t will be later described.
In an earlier work (’98) I came to the conclusion th a t the ascending process of the premaxillary
of teleosts is primarily an independent bone, and th a t this independent bone is represented in th e
median dermal ethmoid of Amia, and probably also in bone 2 of Huxley’s descriptions of Esox. This
conclusion, in so far as it regards the dermal ethmoid of Amia, seems confirmed by the conditions
found in Lophius, Sphyraena, Salmo, Elops, and other fishes th a t I have been led to examine in this
connection. Regarding bone 2 of Esox I have made no further investigation, b u t it would certainly
seem to be the homologue of the dermal ethmoid of Amia.
In Lophius piscatorius, th e premaxillary has a well-developed articular process, b u t no a ttached
ascending process. A t the place where this la tte r process would normally arise, there is a
transverse facet which gives articulation to th e anterior end of a long and tapering bone. This is
all seen in Bruhl’s (’56) figures of this fish, and the long and tapering bone is considered by th a t author
as the detached ascending portion of th e ’ premaxillary (infra-maxillary), which it unquestionably is.
I t lies close against its fellow of the opposite side, the two bones, united, lying in a large rostral
chamber on the dorsal surface of th e snout. No rostral cartilage is found, b u t it is quite unquestionably
represented in the tissues th a t envelope and underlie the two bones. The ascending processes of
the premaxillaries thus here have a shape and position th a t render them easily recognizable as
those processes, which th e dermal ethmoid bones of Amia and Esox have not, and yet, as in these
la tte r fishes, the two bones are wholly independent of the bodies of th e premaxillaries.
In Sphyraena vulgaris the premaxillary has both articular and ascending processes. The
ascending process rests against the antero-mesial edge of the articular process, wholly free from it,
b u t flexibly and apparently uninterruptedly connected with the premaxillary immediately antero-
mesial to th e base of th e articular process. The connection is by the intermediation of what looks
like gristly tissue, and it is evident th a t a primarily independent bone is here in process of fusion
with th e premaxillary. Tha t the bone can not be an outgrowth of the premaxillary th a t is in process
of becoming detached from it, seems self-evident.
In Salmo salar, Parker (’73) shows th e premaxillary as a large and somewhat triangular bone,
the point of the triangle directed dorso-posteriorly and overlapping th e proximal end of th e maxillary.
At th e mesial edge of the bone a sh o rt process is shown which might, in the figure, be considered
as an ascending process. This is, however, probably an error in the drawing, for I have examined
both Salmo tru tta and Christivomer namaycush and do n o t find the process in either. The
premaxillary bone, in both these la tte r fishes, is somewhat triangular, as shown by Parker in Salmo
salar, b u t the dorso-posteriorly directed point of th e triangle lies near th e middle of th e length of
the bone and n o t a t its mesial edge, as an ascending process should. The process, moreover, overlaps
the proximal end of the maxillary, and gives articulation, on its internal surface, to th a t bone.
I t is accordingly a p a rt of th e articular process of th a t bone and not an ascending process. And in
all of these three fishes there is an independent so-called supraethmoid.
In Elops saurus the maxillary has the relation to the premaxillary th a t is designated b y Sage-
inehl as lateral. The premaxillary is without ascending process, and articulates, by its antero-mesial
end, with the antero-lateral edge of a bone th a t Ridewood (’04.a) considers as a mesethmoid firmly
united with a vomer. This mesethmoid bone of Elops is said by Ridewood to be separable without
much difficulty into two components, ,,the upper p a rt (supraethmoid of some authors) being a membrane
bone, while the lower pa rt, of diminutive size is a cartilage bone“. In my two specimens of the
fish this membrane component of the mesethmoid bone is traversed by a cross-commissural canal
which is in communication, a t either end, with th e infraorbital latero-sensory canal. I t was not
possible to establish the presence of sense organs in this canal, b u t it is, nevertheless, quite unquestionably
the homologue of the anterior or ethmoid commissure of the Crossopterygii and Ganoidei
Holostei (Allis, ’04), and it has never heretofore been found in any teleost. The infraorbital canal,
after having traversed the anterior one of the circumorbital bones shown in Ridewood’s figures;
Zoologica. Heft 57. ^