skull, not, accordingly, traversing th e so-called jugular foramen, which foramen is th e facialis opening
of th e trigemino-facialis chamber of my descriptions. This course of these two arteries being so
unusual, I have h ad i t looked up b oth in R hombus and Solea. In both these fishes th e efferent pseudo-
branchial arte ry runs forward external to the cranium, th e external carotid traversing the trigemino-
facialis chamber, both arteries th u s having exactly.the same general course th a t they have in Scorpaena
and th a t they are known to have in many other teleosts. T h a t Pleuronectes forms an exception
to this rule I greatly doubt, th e particular specimen examined by Cole & Johnstone doubtless presenting
an abnormality in th e course of these two arteries, as it apparently does also in th e absence
of an encephalic artery arising from the transverse commissure th a t is said to connect th e internal
carotids of opposite sides.
The internal carotid of Scorpaena, having given off the orbito-nasal arte ry or th e communicating
branch to the efferent pseudobranchial artery, as th e case may be, runs mesially and b u t
slightly anteriorly along the floor of the myodome, lying immediately beneath th e rectus internus
muscle. Having reached th e middlé line of th e head, th e arte ry tu rn s upward between th e two recti
interni muscles, there lying closely pressed against its fellow of th e opposite side. Whether there is
here an anastomosis of th e arteries of opposite sides to form a single, median encephalic artery, such
as Allen describes in Ophiodon, or not, could n o t be determined; b u t there probably is, as, otherwise,
there would be no circulus cephalicus in this fish. I t may, however, here be s tated th a t th e
diagrams ordinarily given of this circulus, and as given by Ridewood (’99) for Cottus and Trigla,
are misleading, for there is not here a simple transverse commissure, such as there is for th e efferent
pseudobranchial arteries. There are two arteries, one on either side, which, running upward to enter
th e cranial cavity, lie close together and fuse in th e middle line for a short distance, and then separate
again as they enter th e cranial cavity. The one or two arteries in Scorpaena, whichever it be, running
upward enters th e hind end of th e median vertical band of fibrous tissue, already described, th a t
arises from th e hind edge of th e pedicle of th e basisphenoid and ends posteriorly in th e fibrous tissues
th a t close the pitu ita ry opening of th e brain case. Having traversed this tissue, the two arteries
become distinct again, perforate separately th e membrane th a t closes th e pituitary opening of the
brain case, along the hind edge of the basispheniod, and enter th e cranial cavity, the ir further course
n o t ’being traced.
In Scomber I have s tated (’03, p. 93) th a t the internal carotid enters th è cranial cavity along
th e anterior edge of th e basisphenoid, there perforating the membrane th a t closes th e orbital opening
of th e brain case. This marked difference in the relations of th e arte ry to the basisphenoid, in this
fish and in Scorpaena, has led me to reexamine Scomber, and I find th a t my statement regarding
th a t fish is an error, the arte ry there running up posterior to the basisphenoid, as it does in Scorpaena^
The vèssel x was examined in sections of young specimens of Scorpaena, Trigla, Lepidotrigla
and Dactylopterus, b u t the results obtained were so unsatisfactory th a t I am preparing material
for a further study of it. I t is so small a vessel th a t it was n o t looked for in any of th e adults.
In the sections examined of Scorpaena, Trigla and Lepidotrigla strictly similar conditions were found,
while in Dactylopterus the vessel presented a slightly different arrangement.
In Scorpaena, Trigla and Lepidotrigla the vessel is formed by th e union of what seem to
be small arteries th a t arise in some sort of relation to the efferent arteries of the first three
branchial arches. Running forward parallel and close to the common carotid, the vessel soon
separates into two pa rts which may be called its internal and external branches. The internal branch
closely accompanies the internal carotid and could be traced as far as the internal carotid foramen,
where it either fused with the internal carotid or vanished in the sections. The external branch
closely accompanies the external carotid until it reaches the facialis opening of the trigemino-facialis
chamber. There it separates slightly from th e carotid, b u t enters and traverses the trigemino-facialis
chamber, lying somewhat dorsal to the carotid. Issuing from the chamber, the vessel separates into
three branches. One of these branches accompanies the sclerotic-iris branch of the carotid artery
and passes into th e cranial cavity with th a t branch of th e la tte r artery th a t traverses the little
foramen in the alisphenoid, already described. A second branch of the vessel closely accompanies
th a t branch of the carotid th a t goes to the levator arcus palatini. The third branch turns backward
and immediately gives off a small b ranch which accompanies th a t terminal portion of the carotid th a t
runs downward to fall into the arteria hyoidea. The remainder of this third branch then continues
backward along the side wall of the s k u ^ ; joins the truncus hyoideo-mandibularis facialis and
traverses, with th a t nerve, th e facialis canal through the hyomandibular. Slightly before it enters
the la tte r canal it sends a branch backward, this branch joining the ramus opercularis profundus
facialis and going to the region of the adductor hyomandibularis and the adductor and levator
operculi. The terminal portion of the third branch of the vessel x of these fishes, this branch being
given off from the external a rte ry a fter th a t a rte ry issues from the trigemino-facialis chamber through
its trigeminus opening, thus has a distribution similar to th a t of a branch of the hyo-opercularis
of Amia given off before th e arte ry enters the trigemino-facialis chamber. In Amia, in fact, this
la tte r branch is th e important p a rt of th e artery, and so led me to call it the hyo-opercularis, the
p a rt th a t enters the trigemino-facialis chamber appearing as a small branch only.
P T E R O T I C .
The pterotic (squamosal) forms a small lateral portion of the dorsal surface, and the dorso-
posterior portion of the lateral surface of the brain case, and the larger p a rt of the lateral wall of
th e temporal fossa. The bone is bounded, as usual, by th e sphenotic, prootic, exoccipital and epiotic
with all of which bones it is in synchondrosis, and by the lateral extrascapular, parieto-extrascapular,
frontal and postfrontal, with which bones it is in sutural contact. The opisthotic overlaps externally
th e outer surface of its postero-ventral portion. On its internal surface there is a large recess which
leads into a canal which lodges th e outer portion of the external semicircular canal.
On the dorsal surface of the bone, near its lateral edge, there is a prominent longitudinal ridge
which ends posteriorly in a short sharp point which forms one of the spines of the lateral row. A
th in flat posterior process projects backward from the dorsal half or two-thirds of th e hind edge of
th e bone, and gives insertion to th e dorsal end of the fibrous membranes th a t line th e anterior and
posterior surfaces of th e opercular opening. Degenerate muscle fibers are found in the dorsal ends
of these membranes. No portion of the tru n k muscles arises from the process. On the dorsal edge
of the process the lateral edges of the lateral extrascapular and suprascapular rest, b u t the process
gives no support to the supraclavicular, such as Sagemehl describes in the Characinidae and
Cyprinidae. On the lateral surface of the bone, close to its dorsal edge and extending nearly the
full width of the body of the bone, there is an oval facet for the posterior articular head of the
hyomandibular, th e facet lying considerably dorsal to th a t portion of the bone th a t lodges the
external semicircular canal. Dorsal to the anterior portion of this facet, a depression on the anterior
edge of the bone forms the posterior portion of the dilatator fossa. The pterotic is traversed by the