p a rt of the dorsal surface of the skull. The postfrontal forms p a rt of th e roof of the dila ta to r fossa,
bears two or three short b lu n t spines, and is traversed by the main infraorbital latero-sensory canal,
lodging one organ of th a t canal, innervated b y th e ramus oticus lateralis.
In Scorpaena porcus, th e postfrontal is a short, small, tubula r bone, and bears b u t one, or a t
most two spines.
P A R I E T O - E X T R A S C A P U L A R .
The parieto-extrascapular is formed b y the fusion of the parietal with the mesial ossicle of the
extrascapular latero-sensory series. This fusion, in certain other fishes, of these two usually separate
elements was fully discussed b y me in a recent work (’04). As further confirmation of th e fusion,
th e conditions in Chanos can be cited, where, according to Ridewood (’04a, p. 58), „ th e parietals are
widely separated in the young b u t by subsequently fusing with th e scales of the commissural section
of th e sensory canal system, they come to meet above the supraoccipital bone”.
In Scorpaena, the parieto-extrascapular is a relatively large and very irregular bone, with a
much ridged dorsal surface. One of these ridges is th e parietal spinous ridge, which has already been
described. Another and lower ridge lies immediately lateral to th e p arietal ridge, is formed, anteriorly,
by the lateral bounding ridge of th e groove on th e vertex, and, posteriorly, by th e nuchal spinous
ridge; the ridge being interrupted between these two portions. Immediately lateral to this ridge,
there is a curved ridge, tall in its middle portion b u t low a t either end, th e hollow of th e curve presented
laterally. The posterior portion of this ridge marks the course of a p a rt of the supratemporal latero-
sensory canal. A mesially projecting comer of th e bone lies on the posterior portion of th e dorsal
surface of the supraoccipital, articulates by suture, usually serrate, with its fellow of th e opposite
side, and forms the summit of th e ridge th a t bounds posteriorly th e groove on the vertex. A large
reentrant angle a t th e postero-lateral comer of the bone receives th e antero-mesial comer of the
lateral extrascapular, th e edges of this p a rt of th e parieto-extrascapular overhanging slightly the
temporal fossa and forming p a rt of its roof.
The posterior half of th e parieto-extrascapular is a stout, broad process-like portion which
projects postero-laterally and lies slightly dorsal to th e dorsal surface of the suprascapular process of
th e epiotic; the narrow space between itself and th a t process of th e epiotic receiving th e epiotic arm
of th e suprascapular. From th e internal surface of this p a rt of th e bone, near its hind edge, a delicate
flange projects ventro-posteriorly. The antero-ventral surface of this flange lies upon th a t p a rt of
th e dorsal surface of the epiotic th a t lies immediately anterior to th e base of th e suprascapular process
of th a t bone. The postero-dorsal surface of th e flange forms p a rt of th e floor of the supratemporal
pocket and thus forms p a rt of the apparent posterior surface of the ad u lt skull, b u t it lies on a p a rt
of the dorsal surface of the primary skull, and n o t on its posterior surface, as already explained.
The anterior half of the parieto-extrascapular rests in p a rt upon th e dorsal surface of the
pterotic and supraoccipital, in p a rt upon remnants of the chondrocranium adjacent to those bones,
while, in part, it bridges the lateral fontanelle of the skull, there forming p a rt of the roof of the cranial
cavity. The anterior edge of th e bone articulates by suture with th e hind edge of th e frontal, the
mesial edges of the parieto-extrascapulars not here meeting in the middle line, and a median portion
of the supraoccipital being exposed between them. The bone is traversed by the supratemporal
latero-sensory canal, th e canal usually lodging a single sensory organ, b u t in one specimen this organ
had apparently separated into two parts, lying close together. In 46 mm specimens there is b u t a
single organ here, this showing th a t b u t a single extrascapular latero-sensory ossicle has here fused
with th e parietal.
The parietal spine on th e dorsal surface of th e parieto-extrascapular belongs to the anterior,
parietal p a rt of the bone, th e nuchal spine belonging to the posterior, extrascapular part.
L A T E R A L E X T R A S C A P U L A R.
The lateral extrascapular, th e only independent extrascapular element there is in the skull of
Scorpaena, is a small plate-like bone th a t forms th e larger p a rt of th e roof of the temporal fossa.
Its lateral edge rests upon th e dorsal edge of the posterior process of the pterotic, and its posterior
edge upon th e dorsal surface of th e suprascapular. Its anterior and mesial edges are almost entirely
enclosed in th e reentrant angle in th e postero-lateral corner of the parieto-extrascapular, from which
bone the extrascapular is separated by a narrow space bridged by fibrous tissue, this tissue holding
the extrascapular in place, forming p a rt of th e roof of th e temporal fossa, and transmitting the supratemporal
canal. The bone encloses a section of the main infraorbital latero-sensory canal, and also
th e lateral portion of the supratemporal canal, lodging one sense organ of each of those canals. The
bone bears, on its hind edge, th e anterior one of the two spines of the intermediate line.
S U P R A S C A P U L A R .
The suprascapular has a mesial, or epiotic, and an inferior, or opisthotic process, the epiotic
process forming th e larger p a rt of the bone and running insensibly into the body of the bone. The
body of th e bone, which forms the lateral edge of the entire bone, encloses a short section of the main
infraorbital canal and lodges one organ of th a t canal. The epiotic process projects upward forward
and mesially, and rests upon th e dorsal surface of the suprascapular process of the epiotic, fitting
closely into a narrow space between th a t bone, below, and the ventral surface of th e projecting posterior
portion of th e parieto-extrascapular above. The process of the suprascapular is firmly bound to each
of these two la tte r bones, its position relative to the posterior portion of the parieto-extrascapular
being th a t th a t i t normally has to an extrascapular bone. The opisthotic process of the bone projects
ventro-antero-mesially and rests upon and is bound by tissue to a thickened portion of the hind edge
of th e opisthotic. The process lies along, or internal to, the hind edge of the posterior process of the
pterotic, and forms th e lateral wall of th e posterior opening of th e temporal fossa.. On the internal
surface of th e postero-lateral corner of the bone, close to its hind end, there is a small articular eminence,
and immediately antero-mesial to this eminence, an articular facet; the two surfaces articulating
with corresponding surfaces on th e dorso-anterior corner of the supraclavicular. The bone bears,
on its h ind edge, two spines, one belonging to th e lateral row of spines and th e other to th e intermediate
row. I t is traversed by the main infraorbital latero-sensory cajial and lodges a single organ of th a t line.
S U P R A C L A V I C U L A R .
The supraclavicular is a triangular bone. I t lies along th e outer surface of the clavicle, and
articulates, by two articular surfaces on its dorso-anterior corner, with the ventral surface of the
suprascapular. One of these two articular surfaces is an articular head th a t rises prominently from
the anterior end of the dorsal edge of the bone, the other being an articular facet th a t lies immediately
latero-posterior to the articular head. The dorsal edge of the bone, posterior to these articular surfaces,