of th e arm of the hone. The space enclosed in this rounded angle is further bounded, latero-anteriorly,
by th e dorsal edges of the lachrymal and palatine, a large oval or rounded passage thus here being
formed, between these several bones, which leads from th e dorsal to th e ventral surface of th e skull
immediately lateral to th e nasal region.
On th e dorsal surface of th e skull, the m esial edge of th e superficial, dermo-perichondrial portion
of th e body of th e ectethmoid is serrated and articulates, by suture, with th e corresponding portion
of th e mesethmoid, th e two bones forming the floor and mesial wall of th e nasal pit. On th e ventral
surface of th e skull th e body of th e ectethmoid everywhere lies directly upon or is in synchondrosis
with th e antorbital cartilage, and is there overlapped externally, along.its mesial edge, b y the lateral
edge of th e parasphenoid. Anteriorly, on th e dorsal surface of th e skull, an interspace of cartilage
separates th e body of th e ectethmoid from th e dorsal limb of th e vomer, this interspace being bounded
mesiafly b y th e mesethmoid. On th e ventral surface of th e skull, in small and even medium-sized
specimens, this same interspace of cartilage intervenes between th e anterior portion of th e body of
th e ectethmoid and th e posteTO-laterally presented lateral edge of th e body of th e vomer; b u t in large
specimens, th e interspace may be cut into two portions by th e backward growth of a process of th e
vomer, this process meeting or even overlapping externally th e anterior edge of th e ectethmoid. The
lateral edge of th e interspace tu rn s slightly, upward, and may present an angle, which then forms a
prominence on th e lateral edge of this p a rt of th e skull. The lateral portion of the ventra l surface
of th e interspace, th e p a rt th a t lies lateral to th e process of th e vomer, when th a t process exists, is
presented ventrally and slightly latero-posteriorly, and gives articulation to a small articular surface
a t th e base of th e maxillary process of th e palatine. In Scomber, I described this articular surface
of the ethmoid cartilage as th e ventro-lateral, or septo maxillary process of th e mesethmoid, i t being
th e mesethmoid instead of th e ectethmoid th a t, in Scomber, forms its principal support. In most
current descriptions of th e teleostean skull, i t is called th e anterior palatine, or prepalatine articular
surface or process, the articular surface on th e outer end of th e ventral process-like portion of the
a rm of th e ectethmoid being called th e posterior palatine or postpalatine articular surface or process.
The posterior surface of th e ectethmoid forms th e concave anterior wall of th e o rb it; th e wing, th e
arm, and th e body of th e bone all contributing to it. A t th e anterior end of th e orbit, and somewhat
above its floor, there is a pit-like depression, lying p a rtly in th e body of th e ectethmoid and pa rtly in
th e adjoining cartilage. The p it gives insertion to th e oblique muscles of th e eye, and is accordingly the
anterior eye-muscle canal. In it, close to its lateral edge, is th e posterior opening of th e olfactory
canal through th e antorbital process, th a t canal being entirely enclosed in th e body of the ectethmoid.
Immediately lateral to th e p it, a strong ligament has its origin, as in Scomber, and running downward
is inserted on a transverse ridge-like process of th e palatine cartilage th a t forms th e hind edge of the
posterior ethmoid articular surface of th a t element. This ligament is thickened a t either edge, thus
seeming to represent two ligaments incompletely fused with each other.
Ridewood says (’04a, p. 56) th a t the ectethmoid (his prefrontal) is usually formed by th e fusion
of originally separate ectosteal and endosteal components, and he says (1. c., p. 39) th a t th e bone is
„purely ectosteal“ in Elops. As, in my work, I have never found a dermal ectethmoid, I have examined
Elops carefully in this connection, and th e bone, in my specimens, is certainly similar to the
bone of Scorpaena: th a t is, it is formed of a perichondrial layer th a t has acquired dermal accretions,
and these accretions do n o t represent a separate dermal component th a t has fused with an underlying
-perichondrial one. T h a t an independent and purely dermal ectethmoid, related to an underlying
endosteal bone, may have existed in earlier fishes, I can n o t Contest, b u t I g reatly doubt it; the apparently
dermal prefrontal described in certain fishes belonging, in my opinion, to the frontal or nasal
series and fusing with one or the other of those bones and not with th e ectethmoid.
V 0 M E R.
The vomer caps the pointed anterior end of th e antorbital cartilage, and has dorsal and ventral
limbs, one of which forms p a rt of the dorsal, and th e other p a rt of th e ventral surface of th e anterior
end of th e skull. The anterior edge of th e bone has the shape of a broad V, the point of the V directed
forward in the middle line; and on th e ventral surface of this edge of the bone there is a narrow
raised surface th e anterior portion of which is garnished with small villiform teeth, the band of teeth
passing uninterruptedly from one side of th e head to the other. This p a rt of the vomer forms the
head of the bone. Posterior to this head, the ventral limb, or body of th e bone projects backward
along th e ventral surface of th e skull as a th in plate which tapers rapidly to a sharp point. In its
anterior portion, the body of the bone lies against the ventral surface of the antorbital cartilage, while
posteriorly it fits into a depressed region on th e ventral surface of the parasphenoid. The bone has
no pronounced lateral processes, such as are found in Scomber, b u t in the angle between th e h ead and
th e body of th e bone, on either side, there is a slight process which projects toward, and in large
specimens may even come in contact with, th e anterior end of the ventral plate of th e corresponding
ectethmoid. This little process has already been referred to, when describing th e ectethmoid, this
la tte r bone and th e process of th e vomer both growing toward and giving support to the anterior
palatine articular process of th e ethmoid cartilage. Immediately anterior or antero-mesial to this
slightly developed lateral process of th e vomer, on the ventral surface of the bone, and slightly
posterior to th e raised portion th a t bears th e villiform teeth, there is a large b u t shallow depression
which gives origin to a strong ligament, the vomero-palatine ligament, which has its insertion on the
mesial surface of th e palatine.
On th e dorsal limb of the vomer there is a median ridge which forms an anterior prolongation of
th e m edian ridge on the mesethmoid. A median interspace of cartilage intervenes between the two bones
and extends forward a variable distance in a median slit in the hind edge of the dorsal limb of the
vomer, this slit separating this limb of the vomer into two parts which m ay be called th e right and left
ascending processes of th e bone. Near th e hind end of th e interspace of cartilage, and immediately
in front of th e mesethmoid, there is a marked angle in th e mid-dorsal line of the cartilage, this angle
lying not far from the middle of the entire internasal ridge. On either side of th e median ridge, there
is, on the dorsal surface of each ascending process of the vomer, a depressed region, and in th e line of
the bottom of this depression, near th e anterior edge of the bone, there is a slight eminence which is
found much more developed in th e Triglidae. With the lateral surface of this eminence, and in the
depressed region posterior to it, th e postero-ventral portion of th e ascending process of th e maxillary
articulates, as will be later described.
The ascending processes of the vomer are each in sutural contact, posteriorly, with the anterior
end of th e perichondrial portion of the mesethmoid; and this posterior portion of these processes
has, in th e adult, strikingly the same appearance as th e adjacent perichondrial portions of the three
ethmoid bones. The vomer can, however, be removed from the skull, in slightly macerated specimens,
without apparently injuring, in th e least, the underlying cartilage. Whether, because of this, the
entire bone should be considered as of purely membrane origin, or not, I can n o t decide; b u t it would
Zoologica. Heft 57. 3