similar process is found on the premaxillary, there lying immediately external to and covering the
antero-mesial end of th e maxillary; and this must he th e articular process of th e bone, if th a t process
is not represented in bone 2 of Huxley’s descriptions.
The articular process of the premaxillary of teleosts would thus seem to be as early, or even
an earlier acquisition of th a t bone th a n th e ascending process. This has led me to reconsider th e
conditions found in Amia, in which fish there is, as is well known, a large posterior process of the
premaxillary, b u t no ascending process. This posterior process I was led, in an earlier work (*98),
to consider as an olfactory sensory ossicle fused with th e premaxillary, this conclusion being largely
based on a description of Gvmnarchus th a t I have since found to be erroneous (Allis, ’04). My p resent
work leads me to consider it as a greatly developed articular process of th e premaxillary; for the
maxillary articulates with its postero-ventral surface (Allis, ’98), as i t should, and its relations to the
nasal sac are such as might be readily acquired b y a posterior prolongation of the process of Scorpaena.
R O S T R A L .
The rostral is a median piece of- cartilage, longer th a n it is tall, and about as tall as it is broad.
Its external, or dorso-anterior surface, which is slightly concave, gives support and attachment, on
either side, to the ascending process of the corresponding premaxillary. Its internal, ventro-posterior
surface is considerably wider th a n th e external one, and is grooved its full-length, in the median line,
the groove fitting upon and sliding backward and forward upon th e median internasal ridge. A short,
sto u t ligament arises from the side of the rostral, and running downward and backward, is inserted
on the mesial surface of w hat I shall describe as th e ascending process of th e maxillary, near its v entral
edge. From th e posterior half of th e latero-ventral edge of th e rostral, and in pa rt, also, from its
ventral surface, arises a tough fibrous or ligamentous band, which is in p a rt inserted on th e pointed
mesial (proximal) end of th e maxillary and in p a rt on th e shank of th a t bone. In th a t p a rt of the
band th a t has this la tte r insertion is suspended the semi-cartilaginous nodule th a t is interposed b e tween
th e articulating surfaces of th e vomer and maxillary.
In Gasterosteus, according to Swinnerton, th e rostral is a chondrification, in late stages of
development, of a mass of densely nucleated tissue, which, in earlier stages, lies chiefly on th e underside
of th e ascending processes of th e premaxillaries. In Salmo, Gaupp (’03) finds th e rostral arising
in exactly th e same manner, and as he had not apparently noticed Swinnerton’s description he considers
the discovery of this development of this cartilage in Salmo as a support to th e assumption
th a t th e premaxillary is a dermal bone developed in relation to a labial cartilage. B u t if th e ascending
process of th e premaxillary is not primarily a p a rt of th a t bone, as I maintain, th e cartilage would
seem n o t to have this special significance. In any event th e rostral is quite certainly n o t a detached
portion of the primordial cranium.
M A X I L L A R Y .
The maxillary is a curved untoothed bone, with a flat, expanded hind end, and a somewhat
complicated anterior end. This la tte r end of th e bone forms its articular head, and may be said to
bear two plate-like processes of bone, so placed as to give to th e end of th e bone a broad and somewhat
Y-shaped appearance. The antero-mesial (proximal) end of the shank of the bone curves ra the r
sharply mesially and lies directly above th e dorsal limb of the vomer, b u t i t is apparently not in sliding
conta ct w ith th a t bone. On its v entral edge there is a pronounced angular eminence, th e dorso-anterior
(lateral) surface of which, and the corresponding surface of th e shank of th e bone above it, bears a
condylar thickening which articulates, by th e intermediation of a pad of semi-cartilaginous tissue,
with the internal (postero-mesial) surface of th e articular process of the premaxillary, th e pad of
tissue being suspended in tissues th a t are attached to th e premaxillary and rostral ra the r th a n to the
maxillary.
On th e dorsal edge of the extreme antero-mesial (proximal) end of the maxillary there is a
email bluntly pointed process which projects dorso-mesially and touches, or almost touches, the ventral
surface of th e rostral, being bound to th a t cartilage by tough fibrous tissue. Beginning a t the base
of this little process, a flange-like process rises from th e dorsal edge of the maxillary, extends distally
a short distance along the shank of th a t bone, and then tu rn s transversely, almost a t right angles,
across its dorsal surface. The process thus has longitudinal and transverse portions, th e la tte r of
which is much th e more important and forms a ta ll flange-like portion of the entire process which lies
perpendicularly to the maxillary and approximately in a vertical longitudinal plane of th e body.
This right-angled and flange-like process may be called th e ascending process of th e maxillary. Into
th e angle between its two portions th e postero-lateral edge of the articular process of the premaxillary
fits, the ascending process of the m axillary thus embracing and giving articulation, in th e angle between
its two parts, to th e edge of the articular process of th e premaxillary. From th e mesial surface of the
transverse portion of the process, a strong ligament, already referred to, runs upward and backward
and is inserted on th e lateral surface of th e rostral, near its ventral edge.
The transverse limb of the ascending process of the maxillary is longer th a n the shank of the
maxillary is wide, and hence projects anteriorly beyond th e lateral edge of th a t shank. The ventral
edge of this projecting portion of th e ascending process is fused with the anterior end of another plate-
like process of th e maxillary, this la tte r process arising in a longitudinal fine from the dorso-anterior
(lateral) surface of th e shank of the bone, beginning immediately distal to th e ascending process.
This longitudinal process, which m ay be called the ligamentary process of the bone, projects downward
and forward, eaves-like, along the anterior (lateral) surface of th e premaxillary. I t gives insertion,
o n the antero-mesial (proximal) corner of its external, dorso-anterior surface, to the ethmo-maxillary
and naso-maxillary ligaments, which ligaments from there run postero-dorso-mesially to their points
of origin on the mesethmoid process and th e nasal bone respectively; th e ligaments, in their course,
lying upon and crossing latero-mesially the anterior edge of the ascending process of the maxillary.
From th e antero-mesial (proximal) edge of th e process a wide band of fibrous tissue arises, and, running
mesially, crosses th e external surfaces of th e ascending processes of the two premaxillaries, near their
bases, and has its insertion on the antero-mesial edge of the ligamentary process of the maxillary of
th e opposite side. The cut ends,- only, of this band are shown in the figures. This intermaxillary
band of tissue, together with the short ligament, on either side, and already described, th a t extends
from th e base of th e ascending process of the premaxillary to the m esial (proximal) end of the ligamenta
ry process of th e maxillary, hold th e two maxillaries against the edges of the articular processes
•of the premaxillaries, the two ligaments being directly opposed to a ligament th a t arises from the
extreme postero-lateral (distal) corner of the ligamentary process. This la tte r ligament runs postero-
ventrally across the dorsal surface of the shank of the maxillary and then onward along th e internal
surface of th a t bone, lying in the th in membrane th a t extends from the inner surface of the maxillary,
near its dorsal edge, to the ventro-lateral edge of the palato-quadrate apparatus, and th a t forms p a rt