minus, lateralis trigemini and ciliaris profundi nerves from its anterior opening. The chamber lodges
th e trigeminus portion only of the trigemino-facialis ganglionic complex, together with the associated
sympathetic ganglia, a recess on th e cerebral surface of th e bone lodging the lateralis and communis
portions of th e ganglionic complex. The chamber might accordingly be more properly called the
trigeminus or semilunar chamber, th e recess on the cerebral surface of the bone being called the
facialis or geniculate recess. B ut u ntil th e manner of development is b e tte r known, of this chamber
and recess, from a single chamber lodging the entire ganglionic complex, as in Amia, it seems to me
best to retain the name already given to th e chamber in Scomber, and to call the recess the tr igemino
facialis recess. The main sympathetic trunk, the jugular vein, the external carotid artery
and th e vessel x all traverse th e chamber in Scorpaena, the chamber th u s representing either
the whole or a portion of the upper lateral chamber of the eye-muscle canal of Amia (Allis, ’03, p. 94).
In to the chamber two to four foramina open; a large trigeminus one, a slightly smaller facialis one,
and two small foramina, one or both of which may be in c lu d e in th e large trigeminus foramen. One
of th e two small foramina, when found, transmits the ramus ophthalmicus lateralis, th e other tra n s mitting
th e truncus ciliaris profundi. The ophthalmicus foramen lies slightly dorso-anterior to
th e trigeminus foramen, this la tte r foramen lying anterior to the facialis foramen, while th e profundus
foramen lies in the internal jugular groove a t a variable distance anterior to the trigeminus
foramen. The trigeminus foramen transmits the radix trigemini, th e ramus buccalis plus oticus
lateralis and the encephalic branch of the jugular vein. The oculomotorius traverses a foramen th a t
perforates the prootic anterior to these several foramina, as will be later described, and in one
instance, this nerve was accompanied, as it traversed its foramen, by th e truncus ciliaris profundi.
Sagemehl says (’91, p. 568) th a t in the Cyprinidae th e ramus ophthalmicus superficialis (trigeminus
lateralis) always perforates the alisphenoid; and Stannius says (’49, pp. 33 & 36) th a t this
same nerve pierces th e alisphenoid (Keilbeinfliigel) in most teleosts. Sagemehl further says (’84b,
p. 70) th a t independent foramina for the truncus trigemini and th e ramus ophthalmicus superficialis
trigemini is a primitive condition, and th a t a single foramen for these two nerves is exceptional.
Neither of these statements is tru e either for Scomber or Scorpaena, and it would seem as if the
foramina referred to must be, as in Amia, th e foramina by which th e nerves referred to issue from a
trigemino-facialis chamber and not those by which they issue from th e cranial cavity to enter th a t
chamber. Tha t there is a radical difference in these two sets of foramina was pointed out in my
work on Scomber, and will be further discussed in the course of th e present work.
The ventral portion of the prootic of Scorpaena, the part th a t lies ventral to the mesial process
of the bone, forms, as usual, the lateral wall of the myodome, and its ventral edge is edged its full
length with a broad band of cartilage, this cartilage being held in a deep slit-like groove in the edge
of the bone. This groove lies between thin external and internal laminae of the prootic, of perichon-
drial origin, the anterior edges of these laminae being united along the anterior edge of the bone.
The anterior edge of the endosteal bone, thus formed, then receives membranous additions which
prolong it anteriorly, especially in its dorsal portion. Ventro-mesial to this edge of the bone, the
ventro-anterior corner of the edging band of cartilage is cut away to form a large incisure which
bounds the passage for the internal carotid artery. Posterior to this incisure the ventral edge of the
edging cartilage forms the lateral boundary of the hypophysial fenestra, the ventral edge of the
cartilage being presented ventro-mesially and abutting against the lateral surface of the median
ridge on the dorsal surface of the postorbital portion of the parasphenoid.
The ventral edge of this ventral portion of the prootic is overlapped externally by the lateral
edge of the body of the parasphenoid, its anterior edge being in part overlapped externally by, and
in part suturating with the hind edge of the ascending process of the same bone. In the angle between
the ascending process and the body of the parasphenoid, between that bone and the prootic, is the
internal carotid foramen, which leads from the external surface of the skull inward and forward
between the parasphenoid and the prootic, and then across the internal carotid incisure, into the
myodome. On the external surface of the prootic, and running from the dorsal edge of the internal
•carotid foramen upward and backward toward the facialis opening of the trigemino-facialis chamber,
there is a slight groove which marks the course of the internal carotid artery before it enters the
foramen. Immediately anterior to this groove, on the lateral surface of the ascending process of
the parasphenoid, the infrapharyngobranchial of the first branchial arch is flexibly attached by strong
fibrous tissues.
The mesial process of the prootic forms, as usual, part of the roof of the myodome and part
of the floor of the cranial cavity. The angle between it and the ventral part of the bone forms the
dorso-lateral angle of the myodome, and in this angle, near its anterior end, there is a deep pit leading
upward in the bone almost to the floor of the trigemino-facialis chamber; a remnant, doubtless, of
the passage which, in Amia, connects the ventral portion of the myodome with its upper lateral
chamber. Immediately anterior to this pit is the ventral opening of the canal for the palatinus facialis,
that canal beginning on the cerebral surface of the bone, in what has already been referred
to as the trigemino-facialis recess. The canal lies wholly in a part of the bone that is of membranous
origin, as will be later explained.
The dorso-lateral angle of the myodome is well rounded, and is continued forward upward
and laterally to the internal jugular notch, where, turning backward, it falls into and is continuous
with the anterior end of the internal jugular groove. The internal jugular notch, as already fully
described when describing the alisphenoid, lies between the dorsal end of the ascending process of
the parasphenoid and the ventral, process-like end of the anterior one of the two little ridges on
the external surface of the alisphenoid, and the internal jugular groove, beginning there, runs backward
and laterally along the orbital surface of the prootic into the ventral end of the trigeminus
opening of the trigemino-facialis chamber. The slight ridge on the prootic that forms the ventral
edge of the groove is closely applied, in its anterior portion, to the inner surface of the dorsal edge
of the ascending process of the parasphenoid, while posteriorly it is continuous with the anterior
edge of the lateral wall of the trigemino-facialis chamber. In the dorso-lateral angle of the orbital
opening of the myodome, immediately mesial to the internal jugular notch, is the external opening
•of the oculomotorius foramen, th a t foramen lying wholly in the prootic. Dorsal to the internal jugular
groove, on the orbital surface of the prootic, there is often a slight ridge with a process-like and downwardly
projecting ventral end, exactly similar to the two ridges on the alisphenoid. The processlike
end of this prootic ridge is, like the processes on the alisphenoid, connected by fibrous tissue
with the dorsal edge of the ascending process of the parasphenoid, the process and tissue evidently
representing an anterior extension of the lateral bounding wall of the trigemino-facialis chamber.
In Amia the lateral bounding wall of the trigemino-facialis chamber is well developed, being
wholly of bone or cartilage, while the mesial wall is wholly of membrane. In Scorpaena, and also
in Scomber, it is the mesial wall that is well developed, the outer wall being greatly reduced, while
Lepidosteus presents a condition intermediate between Amia and Scorpaena.