of the recess. The membranes closing this recess toward the cranial cavity were n o t investigated,
b u t th e recess is certainly a myodomic recess, similar to, and as well developed as, th a t recess in
Gadus. Uranoscopus thus has a myodome of th e kind found in Gadus. I t furthermore has a prootic
vacuity larger even th a n th e vacuity in Gadus, and which, as in Gadus, extends posteriorly into
th e anterior end of th e basioccipital.
In Blennius gattorugine th e posterior portion of th e ventral edge of th e prootic is thick and
grooved, the mesial edge of this groove representing th e mesial process of the bone, and the other
edge representing the ventral portion of th e body of the bone. Anterior to the groove th e actual
ventral edge of th e bone is formed by th e mesial edge of its mesial process. This edge of the bone,
as also both edges of the posterior, grooved portion, are widely separated from th e corresponding
portions of the bone of th e opposite side, th e space between th e mesial processes being bridged by
a membrane w hich underlies the hypoaria and p itu ita ry body. Anteriorly, this membrane is a ttached
to th e hind edge of th e basisphenoid, th a t bone being, in this fish, unusually wide in an antero-posterior
direction. Beneath this membrane and the basisphenoid, between them and th e underlying pa ra sphenoid,
there is a long and relatively large space which lodges certain of th e eye muscles and is
accordingly a well developed and perfectly normal myodome. The p itu ita ry opening and the hypophysial
fenestra are simply unusually large, and the p itu ita ry opening lies much further posteriorly
th a n in Scomber and Scorpaena.
In Lophius piscatorius there is, in th e prepared skull, no myodome, as Vrolik has stated.
In th e fresh skull, however, there is a pocket between th e bony floor of th e skull and an overlying
membrane, and in this pocket certain of th e eye-muscles have their origin. The pocket is accordingly
a myodome. The overlying membrane is thick and strong, and forms th e hind wall of th e orbit as
well as th e roof oi th e myodome. Laterally, on either side, it extends upward and forms, as in Amia,
th e mesial wall of th e trigemino-facialis chamber. The membrane is thus similar to th a t in Amia,
b u t it is even more extensive th a n in th a t fish, for it entirely replaces, in Lophius, th e bony mesial
processes of th e prootics.
In both Syngnathus and H ippocampus, which I have examined in serial sections, there is a large
myodome, roofed, in Syngnathus, entirely by membrane, while in Hippocampus the recti externi extend
backward beyond the other muscles and pass beneath the cranial floor, between it and the parasphenoid,
In Gymnarchus, of th e Mormyridae, a dilapidated skull of which I have, there is apparently
no myodome, th e conditions here being similar to those found in Ameiurus, which will be later described;
b u t in two other members of th e family, Mormyrops deliciosus and Petrocephalus bane,
Ridewood (’04b) says there is a myodome.
In Osteoglossum Leichardti and Heterotis niloticus, of th e Osteoglossidae, Ridewood (’05a)
says there is a myodome; as there also is, according to the same author, in Pantodon Buchholzi and
Phractolaemus Ansorgii.
In Galaxias of th e Galaxiidae, Swinnerton (’03) says there is a myodome.
In Pleuronectes platessa, Cole & Johnston (’01, p. 13) say there is a myodome.
In Echeneis, of Boulanger’s Discocephali, I find, ventro-antero-mesial to the trigemino-facialis
chamber, a large aperture, which, in th e prepared skull, leads directly into th e cranial cavity, along
its floor. The aperture is bounded dorso-mesially by a bone th a t must be the basisphenoid, although
th e sutures in this region can n o t be distinguished in my one specimen; and from the hind 6dge of
this bone a strong membrane extends, in the recent state, backward and downward and is attached
to the floor of the cranial cavity.. Through the aperture and into th e space roofed by this membrane,
certain of the eye muscles extend, the space thus being a perfectly normal myodome.
Of th e Cottidae, said by Cope to be without a myodome, I have described it in the present
work, well developed, in Cottus octodecimospinosus; and Gill (’91b) gives as one of the characteristics
of his family Cottoidea, „Myodome more or less, developed“ .
Of th e Rhamphocottidae, I have no specimens, b u t th e Cottidae having a myodome, certainly
well developed in some species, it must surely be also found in the closely related Rhamphocottidae.
In Gonorhynchus greyi, Ridewood (’05b) says there is a myodome.
Of the entire list of fishes said to be w ithout a myodome, all of the individual species mentioned,
excepting only Caularchus, Callionymus, Fistularia, Cyclothone, Silurus and the eel, are thus shown
to have th a t canal; while of the several families in which the canal is said to be absent, some one or
more members of each family, or of a closely related subfamily, are also shown to have it, excepting
only the Cyclopteroidea, Cromeriidae, Gobiidae, Gobiesocidae, Stomiatidae, Batrachididae and
Comephoridae. Of th e Cyclopteroidea, Cromeriidae, Gobiesocidae, Stomiatidae, Batrachididae and
Comephoridae, I have no specimens; neither have I of Caularchus, Callionymus, Fistularia or Cyclothone.
These fishes must accordingly be left out of consideration. Of Fistularia, it may, however,
be s tated th a t Swinnerton shows a myodome in Gasterosteus, and th a t I find a well-developed myodome
in Centriscus, both of which fishes belong with Fistularia to th e Hemibranchii. Of the Siluridae,
Muraenidae, and Gobiidae, I have specimens and they can now be considered.
In Conger conger of the Muraenidae, there is, a t the hind end of the orbit, a small median
transverse shelf of bone which projects forward slightly above the parasphenoid. The optic nerves
leave th e cranial cavity along the dorsal surface of this shelf, and beneath it, between it and
th e parasphenoid, the recti musclés have their origins. The bones of th e skull are here all so
firmly ankylosed in my specimens th a t I can not with certainty identify them, b u t the shelf of bone
must certainly be either a basisphenoid, a prootic bridge similar to the bridge of Gadus, or a transverse
ridge of th e parasphenoid, as in Dactylopterus. And in either case the little space between
th e bone and the body of the parasphenoid would be a perfectly normal b u t very much reduced
myodome. In a series of sections th a t I have of a young Conger, the recti muscles all seem to
arise from a delicate median membrane, which lies pa rtly beneath and pa rtly anterior to the shelf
of bone, each muscle arising directly11 opposite its fellow of the opposite side; no one of the muscles,
apparently, having its origin either on the shelf or on the parasphenoid bone.
In a single small specimen of Gobius cruentatus th a t I have been able to obtain, the arrangement
seems to be exactly similar to th a t in Dactylopterus. The prootic has a narrow orbital surface
which lies a t a slight angle to th a t p a rt of the bone th a t lies immediately posterior, to it. and th a t
forms the uniformly thin floor of this p a rt of the cranial cavity. The narrow orbital surfaces of the
bones of opposite sides are separated by a wide median interval, and the ventral p a rt o f this interval
is filled by a transverse ridge on the dorsal surface of the parasphenoid. This ridge on the parasphenoid
has th e same antero-dorsal inclination as the orbital surfaces of the prootics, and forms
the hind wall of a small pocket which lies a t the hind end of the orbits, and recalls both.the myodomic
pocket of Gadus, and the myodome of Dactylopterus.
Of Silurus I can find no description th a t is of value in this connection. B ut McMurrich’s
(’84) descriptions of Ameiurus catus (nebulosus) are of value, and, as I have a few specimens of this
fish, it can be described. Short reference must, however, first be made to Sagemehl’s descriptions of