there is, in Trigla, a slight projecting ledge, this being much more marked in my small specimens
th an in th e large one used for the drawings. The hind edge of this ledge, in th e small specimens,
projects posteriorly as a sharp angle, and beneath this p a rt of the ledge the dorsal surface of th e
condylar process of the exoccipital gives support to the lateral portion of the base of the first v ertebral
arch. The mesial and larger portion of the base of the arch rests upon a portion of the dorsal surface
of the articular process of th e independent centrum of the first vertebra, this surface of contact lying
postero-mesial to and contiguous with th e supporting surface on the exoccipital. The arch does n o t
come into contact with the basioccipital.
The mesial process of th e exoccipital, so well developed in Scorpaena, is b u t slightly developed
in Trigla. I t is directed ventro-mesially, a t about 45°, its ventral end, which is widely separated
from its fellow of th e opposite side, resting upon a small process-like portion of th e dorsal surface
of th e basioccipital, this p a rt of th e basioccipital forming th e mesial wall of the hind end of th e
saccular groove.
The BASIOCCIPITAL is broad and relatively short. Its anterior end is deeply and widely
excavated b y the hind end of th e myodome, a narrow, longitudinal, and slit-like opening leading
from this groove onto the outer surface of th e bone. That p a rt of the basioccipital th a t forms the roof
of th e myodome is flat and inclines downward and backward almost a t an angle of 45 °, th e wide and
relatively shallow saccular groove of either side being, in consequence, pushed on to what appears
as a lateral portion of th e cerebral surface of the bone, and being also tilted upward a t a considerable
angle. The hind end of th e saccular groove forms a recess in th e basioccipital, and between th e
recesses of opposite sides there is, on the dorsal surface of th e bone, a large median p it which is the
cavum sinus imparis. Posterior to this pit, and a t a considerably higher level, a short portion of th e
dorsal surface of th e bone forms the floor of th e foramen m agnum. The hind end of the bone is irregular,
th e appearance being th a t of th e ordinary vertebra-like hind end of this bone, with th e dorso-lateral
comers deeply cu t away. This leaves a depressed surface on either side of th e dorsal portion of th e
hind end of th e bone, and this depression receives and gives support to th e anterior articular process
of th e first vertebra. On th e lateral surface of th e hind end of the bone there is a flattened surface
which gives origin to th e occipito-supraclavicular ligament.
The centrum of th e FIRST FREE VERTEBRA is an irregular disk of bone without attached
dorsal arch. The posterior surface of th e disk has th e usual concave vertebral depression, while on
its anterior surface there is simply a flat or slightly concave median portion. From th e dorso-lateral
portion of the centrum, on either side, a s tout process projects antero-laterally, rests upon the basioccipital
in th e depressed region a t th e dorso-lateral corner of its hind end, and there articulates
with the condylar process of the exoccipital. The bases of these two anterior articular processes of
th e first centrum are joined by a s tout web of bone which forms a shelf projecting forward from th e
dorsal edge of th e centrum, th u s making th e dorsal surface of th e centrum much wider, antero-
posteriorly, th a n its ventral surface. On either side of the dorsal surface of th e centrum there is a
depression which receives th e ventral surface of an anterior process of the second vertebra, this la tte r
process bearing and being fused with th e base of th e preforaminal portion of th e arch of its vertebra.
This process of the second vertebra, in small specimens, b u t n o t in th e ’large one used for the
figures, extends, in its lateral portion, almost to the anterior end of the corresponding process of th e
first vertebra, th e free arch of this la tte r vertebra thus appearing, in lateral views, to rest almost
entirely upon the condylar process of the exoccipital. This appearance is however deceptive, for,
as s tated when describing th e exoccipital, the postero-mesial and larger portion of the base of the arch
o f the first vertebra rests upon the mesial portion of th e dorsal surface of th e anterior process of its
own centrum. The dorsal arch of the first vertebra is represented by two bones, one on either side,
which touch in th e mid-dorsal line above the spinal cord b u t are n o t there ankylosed with each
other. On th e lateral surface of each half of the arch, there is a deep p it which gives insertion to the
most anterior rib. Ventral to this pit, the base of th e arch is perforated b y a foramen which transmits
th e first spinal nerve. The base of the second arch is similarly pierced by a large foramen which
tran sm its the second spinal nerve; and dorsal to this foramen there is, on th e lateral surface of the
arch, a large depression which gives insertion to th e second rib. The two halves of this arch of the
second vertebra meet and ankylose in the mid-dorsal line above the spinal canal, but, like the arch
o f th e first vertebra, this arch does not extend dorsally beyond the point of ankylosis; these two
arches being much shorter th a n th e next following ones.
The POSTERIOR SURFACE OF THE SKULL of Trigla differs somewhat from th a t of
Scorpaena. I t slopes rapidly downward nearly to the level of the large foramen magnum, and then
curves ra th e r abruptly backward to form the nearly straight and horizontal dorsal edge of th a t
foramen. Each half of the surface is separated into two portions by the nearly vertical epiotic ridge,
and across the dorsal portion of th e mesial one of these two portions there is a large and rounded
transverse ridge. This ridge is formed entirely by th e epiotic and supraoccipital, and apparently
corresponds to what I have described, in Scorpaena, as th e hind edge of the primary skull; this
being more evident in Trigla gurnardus th a n in Trigla hirundo. Such being the case, the slightly
depressed region, on either side, between the transverse ridge and the hind edge of the secondary
skull would correspond to th e supratemporal pocket aof Scorpaena.
The TEMPORAL FOSSA is relatively small, as compared with Scorpaena. Its posterior
opening is bounded mesially and laterally, respectively, by the epiotic ridge and the opisthotic process
o f the suprascapular, the la tte r process lying in a nearly vertical longitudinal plane, instead of, as
in Scorpaena, in the inclined plane of the lateral surface of the skull. Because of this position of the
opisthotic process of th e suprascapular, there is a large opening leading into th e fossa from the lateral
surface of the skull. In the mesial wall of the fossa there is a large b u t low preepiotic fossa, this fossa
being simply a pocket-like diverticulum of the temporal fossa. The roof of the fossa is formed mainly
b y th e suprascapular and lateral extrascapular, b u t pa rtly also b y projecting edges of the epiotic,
pterotic and parieto-extrascapular.
The SUPRAOCCIPITAL has a large postero-ventral limb which forms a large median portion
o f th e posterior surface of the skull. A small median ridge near the dorsal end of this limb of the
bone represents the much reduced spina occipitalis. The dorsal limb of the bone is completely covered
b y th e overlying parieto-extrascapulars excepting only a narrow hind edge an d .a small and variable
portion of its dorsal surface which lies slightly anterior to th a t hind edge. The anterior edge of this
limb of the bone bounds and is continuous with th e hind edge of th e post-epiphysial cartilage, its
lateral edges bounding, on either side, the posterior portion of the lateral cranial fontanelle.
The EPIOTIC has a s tout suprascapular process, this process and also the dorsal surface
o f th e bone itself, being entirely covered, dorsally, by overlying portions of the suprascapular and
parieto-extrascapular; the epiotic thus being wholly excluded from the dorsal surface of the skull.