The osseous fishes are occasionally devoid
of any exoskeleton. Sometimes they present scattered
dermal plates of true bone; or, as in the Trunkfishes
), the body may be encased in a complete cuirass, which is
calcified, but has not the structure of bone. Again, as in the
), the skin may be beset with innumerable
small spines, somewhat like those which form the shagreen of
in appearance, though they differ from them
in structure. But, usually, the exoskeleton of the Teleosteans
takes the form of overlapping scales, which rarely exhibit the lacunae
characteristic of true bone. The free portions of the
scales are sometimes smooth, and rounded at the edge, when
they are termed cycloid
; or they are roughened with ridges
and minute spines, when they are called ctenoid
|Fig. 44. - The cartilaginous cranium of the Pike (Esox lucius), with its intrinsic ossifications;
viewed, A, from above; B, from below; C, from the left side: N, N, nasar fossae; I. Or, Interorbital septum; a, groove for the median ridge of the parasphenoid; b, canal
for the orbital muscles. Sq., wrongly so marked, is the Pterotic. V. and VIII. mark
the exits of the fifth and pneumogastric nerves; 3, 3, small ossifications of the rostrum.
The spinal column always presents ossified vertebral centra,
and the primordial cartilage of the skull is more or less
replaced by bone. The centra of the vertebrae are usually biconcave,
each face presenting a deep conical hollow. In certain Eels (Symbranchus
), the centra of most of the vertebrae
are flat in front and concave behind, the most anterior possessing
a convexity in front. In many Siluroid fishes a certain
number of the anterior vertebrae are anchylosed together,
and with the skull, into one mass, as in the Ganoids.
The vertebrae are distinguishable only into those of the
trunk and those of the tail. The latter are provided with complete
inferior arches traversed by the caudal artery and vein.
The former usually possess ribs, but these do not unite with
one another, nor with any sternum, in the ventral median line,
and they enclose the thoracico-abdominal viscera. The vertebrae are commonly united by zygapophyses, or oblique processes,
placed above the centra; in addition to which, the
lower margins of the centra are, not unfrequently, united by
additional articular processes. Transverse processes commonly
exist, but the ribs are articulated with the bodies of the
vertebrae, or with the bases of the transverse processes, not
with their extremities.
When a dorsal fin exists in the trunk, its rays are articulated
with, and supported by, elongated and pointed bones -
the interspinous bones,
which are developed around preexisting
cartilages, and lie between, and are connected with, the
spines of the vertebrae. The fin-rays may be entire and completely
ossified, or they may be transversely jointed and longitudinally
subdivided at their extremities. Not unfrequently,
the articulation between the fin-rays and the interspinous bone
is effected by the interlocking of two rings-one belonging to
the base of the fin-ray and its included dermal cartilage, and
the other to the summit of the interspinous bone-like the
adjacent links of a chain.
In all Teleostean fishes the extremity of the spinal column
bends up, and a far greater number of the caudal fin-rays lie
below than above it. These fishes are, therefore, strictly
speaking, heterocercal. Nevertheless, in the great majority
of them (as has been already mentioned, page 19), the tail
seems, upon a superficial view, to be symmetrical, the spinal
column appearing to terminate in the centre of a wedge-shaped
hypural bone, to the free edges of which the caudal fin-rays
are attached, so as to form an upper and a lower lobe, which
are equal, or subequal. This characteristically Teleostean
structure of the tail-fin has been termed homocercal-a name
which may be retained, though it originated in a misconception
of the relation of this structure to the heterocercal condition.
|Fig. 45. - Longitudinal and vertical
section of a fresh Pike'a
skull. - The cut surface of ourttilage
is dotted. For S. V. C. and P.V.G., read a.s.c., anterior,
and p.s.c., posterior
semicircular canal; x, the
parasphenoid; y, the basi
sphenoid; Vo, the vomer P., the pituitary fossa.
In no Teleostean fish is the bent-up termination of the
notochord replaced by vertebrae. Sometimes, as in the Salmon
(Fig. 6, page 20), it becomes ensheathed in cartilage, and
persists throughout life. But, more usually, its sheath becomes
calcified, and the urostyle thus formed coalesces with
the dorsal edge of the upper part of the wedge-shaped hypural
bone, formed by the anchylosis of a series of ossicles, which are
developed in connection with the ventral face of the sheath of
In the caudal region of the body, interspinous bones are
developed between the spines of the inferior arches of the vertebrae, and bear the fin-rays of the anal, and, in part, of the
differ very much in the extent to which the
primordial cranium persists throughout life. Sometimes, as
in the Pike (Figs. 44 and 45), it grows with the growth of the
fish, and only becomes partially ossified; in other cases it almost
disappears. A basi-occipital (B. 0.
), ex-ocoipital (E. 0.
and supra-occipital (S. 0.
) bone are developed in it, and form a
complete occipital segment. The proper basi-sphenoid (BS
bone is always a very small, and usually somewhat Y-shaped,
bone. The alisphenoids (AS.
) sometimes are and sometimes
are not developed. The presphenoidal and orbitosphenoidal
regions commonly, but not always, remain unossified.
In most osseous fishes, the base of the skull in front of the
basisphenoid is greatly compressed from side to side, and
forms an interorbital septum (I Or.
). The anterior moiety of
the cranial cavity is consequently reduced
to a comparatively narrow passage
above the septum (Fig. 45). In
the Siluroid and Cyprinoid fishes,
however, this septum is not formed,
and the cranial cavity is of nearly equal
size throughout, or gradually diminishing
forward. The ethmoidal cartilage
usually remains unossified, but sometimes,
as in the Pike, ossification may
take place in it. (Fig. 44, 3, 3.) The
antorbital, or lateral ethmoidal, processes
of the primordial cranium ossify,
and give rise to the prefrontal
). The postorbital processes
also ossify as postfrontals (Ptf.
The upper and posterior part of the
primordial cranium exhibits five processes-one postero-median, two postero-
lateral, and two postero-external.
The postero-median ossifies as part of
the supra-occipital (S. 0.
). The postero-lateral ossifies as part of the epiotic
), which lies upon the summit
of the superior vertical semicircular
canal. The postero-external closely
corresponds with the squamosal of the
in position; but, as
a cartilage bone, it corresponds with
an ossification of the capsule of the ear,
in the higher Vertebrata
Not unfrequently, as in the Cod, for
example, the opisthotio (Op. O.
) is a
distinct bone, and enters into the formation
of the postero-external process.
The prootio (Pr. 0.
) is always a welldeveloped
bone, and occupies its regular
place, in front of the anterior vertical
semicircular canal, and behind the
exit of the trigeminal nerve.
|Fig. 46. - Side and upper views of the skull of a Pike (Esox lucius), without the facial or
supra-orbital bones: y, the basisphenoid; z, the alisphenoid; a, the articular fecet for
the hyomandibular bone.
In addition to these cartilage
bones, the brain-case of osseous fishes
is additionally defended by numerous membrane bones. These are, on the roof of the
1. The parietal bones (Pa
.), which sometimes meet in a
sagittal suture, as in most of the higher Vertebrata
, but are
very generally separated by the junction of the frontals
2. The large frontals (Fr.
), which may or may not unite
3. The nasal bones (Na.
), apparently replaced in the Pike
by the bones 1 and 2.
The under-surface of the skull possesses two membrane
bones: in front the vomer
), and, behind, the huge parasphenoid
), which ensheathes all the basis cranii
the basi-occipital to the vomer.
A supra-orbital bone (S. Or.
) is the only membrane bone
attached to the sides of the brain-case. Two premaxillary
) are attached, sometimes closely, sometimes
loosely, to the anterior extremity of the cranium; and behind
these are the maxillae (Mx.
), which are sometimes large and
single, as in the Cyprinoid fishes, but may become subdivided,
or be reduced to mere styliform supports for cirri, as in many
Siluroid fishes. In most osseous fishes the maxillae take little
or no share in the formation of the gape, which is bounded
above by the backwardly-extended premaxillae.
|Fig. 47. - Side-view of the skull of a Pike (Esox lucius): Prf, prefrontal; II. M hyomandibular
bone; Op, operculum; S.Op., suboperculum; L. Op, interoperculum; Pr, Op,
preoperculum; Brg, branchiostegal rays; Sy, symplectic; Mt, metapterygoid; Pl, palato-pterygoid arch; Qu, quadrate bone; Ar, articular; An, angular; D, dentary: S.Or, suborbital bone.
The palato-quadrate and hyomandibular have essentially
the same structure and arrangement as in Lepidosteus
, The homologue of the suspensorium of the Elasmobranchii
is articulated with a surface furnished to it by the
postfrontal, pterotic, and prootic bones. Usually it moves freely upon that surface, but, in the Plectognathi
, it may be
fixed. It ossifies so as to give rise to two bones: an upper
), with which the operculum articulates; and a lower styliform symplectic
), which fits into
a groove on the inner and posterior surafce of the quadrate,
and is firmly held there.
The palato-quadrate arch is represented by several bones,
of which the most constant are the palatine (Pl.
) in front, and
the quadrate (Qu.
) behind and below. Besides these there
may be three others: an external, ectopterygoid
), and a metapterygoid
The last envelops the upper and posterior portion of the
primitive quadrate cartilage; and, fixing itself against the
hyomandibular, contributes to the firmness of the union already
effected by the symplectic.
Meckel's cartilage (Mck.
) persists throughout life, but the
ossification of its proximal end gives rise to an os articulare
in the lower jaw. To these an angular (An.
) and a dentary
) membrane bone are commonly added (Fig. 47).
|Fig. 48. - Palato-quadrate arch, with the hyomandibular and symplectic of the Pike, viewed
from the inner side; the articular piece (Art), of the lower jaw, and Meckel's cartilage
(Mck.) of the Pike; seen from the inner side: a, the cartilage interposed between the hyomandibular (H.M.), and the symplectic (Sy); b, that which serves as a pedicle to
the pterygo-palatine arch; c, process of the hyomandibular with which the operculum
articulates; d, head of the hyomandibular which articulates with the skull.
The hyoidean arch is usually composed of two large cornua - connected with the cartilaginous interval between the hyomandibular
and the symplectic by a stylohyal
abutting, in the middle line below, upon one or more median
pieces, the anterior of which (entoglossal
) supports the tongue,
while the posterior (urohyal
) extends back to join the median
elements of the branchial apparatus. The cornua themselves
are usually ossified into four pieces: an upper (epihyal
) and a
) large ossification, and two small ones (basihyals
connected with the ventral ends of the lower large
There are usually five pair of branchial arches connected
by median ventral ossifications. The posterior pair are single
bones, which underlie the floor of the pharynx, bear no branchial
filaments, but commonly support teeth, and are called hypopharyngeal
bones. In certain osseous fishes, thence
, they anchylose together into one bone.
The anterior four pair are composed of several joints, and the
uppermost articulations of more or fewer of them usually
expand, bear teeth, and form the epipharyngeal
important membrane bones are connected with the mandibular
and hyoidean arches. The preoperculum
, (P. Op.
, and branchiostegal
), already met with
among the Ganoidei
, are the most constant of these. Beneath
the operculum, lies a suboperculum
), and below this
), which is connected by ligament
with the angular piece of the lower jaw, and is also united to
the outer face of the hyoidean arch. It may be altogether
ligamentous, as in the Siluroids.
The branchiostegal rays are attached partly to the inner,
and partly to the outer, surface of the hyoidean arch. They
support a membrane, the branchiostegal membrane
serves as a sort of inner gill-cover.
possess two pair of limbs, the pectoral and
the ventral fins. But the latter are often absent, and the
former are occasionally wanting. When the pectoral fins are
absent, the pectoral arch usually remains, though it may be
reduced to little more than a filament, as in Muraenophis,
The ventral fins are frequently situated in their normal position
beneath the posterior part of the trunk; but in considerable
groups of these fishes they are immediately behind the
pectoral fins (thoracic
), or even in front of them (jugular
In the asymmetrical Pleuronectidae
one pectoral fin may be
larger than the other, or may alone remain, as in Monochirus
|Fig. 49. - The bones of the pectoral arch and fore-limb of the Pike (Esox lucius): A, a
semi-diagrammatic view of these bones, to show their relative natural position. The
clavicle (Cl) is supposed to be transparent. S.cl, supra-clavicula; p.cl, post-clavicula c, d, the posterior and anterior ends of the outer margin of the scapulo-coracoid. - B, the
scapulo-coracoid and limb separate and on a larger scale; Scp, scapula; Or, coracoid
a, basal cartilages; b, fin-rays; c, corresponds with c in the foregoing figure.
The pectoral arch always consists of a primarily cartilaginous coraco-scapular
portion - which usually ossifies in two
pieces, a coracoid below, and a scapula above - and of sundry
membrane bones. The chief of these membrane bones is the clavicula
), which meets its fellow in the middle line, and
is usually joined to it by ligament, but sometimes, as in the
Siluroids, by sutural union. By its inner surface it gives
attachment to the coraco-scapular - and sometimes above
them, to a styliform bone which extends back among the
lateral muscles-the post-clavicula (p.cl.).
Attached to the dorsal end of the clavicle, there is usually
a second much smaller bone, the supra-clavicula
this is very generally connected with the skull by a superficial
membrane bone, the post-temporal
, which, in front, becomes
forked, and attaches itself by one prong to the epiotic bone,
by the other to the pterotio, or lower down to the side of the
cranium. The base of the fin contains a series of not more
than five, more or less ossified, cartilages, which are placed
side by side and articulate with the coraco-scapular; to these
succeed one or more rows of small cartilages, partially hidden
by the bases of the exoskeletal fin-rays. The most anterior
of these basal cartilages (the mesopterygial basale) is enclosed
by the base of the anterior fin-ray, and effects that articulation
with the shoulder-girdle which is so remarkable in many solenoid fishes.
The posterior cartilage, or bone, is the metapterygial
basale, and the intermediate three are radialia (p. 39).
possess teeth, and, in the majority of these
fishes, teeth are very widely distributed over the surface of
the walls of the oral and pharyngeal cavities. The teeth very
very much in structure; ordinarily, they consist of dentine,
capped with structureless enamel. The parietes of the tooth
are not unfrequently longitudinally folded toward the base,
but this folding never goes so far as in the Ganoids. The different
kinds and modes of arrangement of the teeth may be
classified as follows:
1. Isolated, more or less pointed teeth, developed from
papillae of the mucous membrane, which do not become enclosed
in sacs-frequently anchylosed to the subjacent bone,
but not imbedded in alveoli, nor replaced vertically. The great
majority of ordinary osseous fishes have teeth of this kind.
2. Isolated teeth, which become imbedded in sockets, and
are replaced vertically.
Such teeth are seen in the premaxillae of Sargus
they curiously simulate the form of human incisors; and, imbedded
in the coalesced hypopharyngeal bones, in Labrus.
3. Isolated teeth, imbedded in the substance of the bone
which supports them. The teeth and the supporting bone
wear away in front, and are replaced by new teeth developed
behind the others. This structure is seen in the coalesced
hypopharyngeal bones of the Parrotfish (Scarus
4. Beak-like compound teeth, attached to the premaxillae
and dentary bones of the mandible.
These are of two kinds. In the Parrotfish (Scarus
beak is formed by the union of numerous separately-developed
teeth into one mass. But in the Gymnodonts (Tetrodon
) the beak is produced by the coalescence of broad
calcified horizontal lamellae thrown off from a subjacent pulp.
5. In the Carp and its allies the basi-occipital sends down
a median process, which expands at the end, and supports a
broad, thick, horny tooth.
The stomach is usually wide and sac-like, but sometimes
(in Scomberesoces, Cyprinoids
, and others) is not wider than
the intestine. Occasionally, as in Mugil
, it acquires thick
walls and becomes gizzard-like. The commencement of the
small intestine is very generally marked by the presence of
more or less numerous caecal diverticula, the pyloric caeca
The small intestine has no spiral valve, though the mucous
membrane may be raised into large transverse folds. The rectum
does not terminate in a cloaca, and almost always opens
quite separately from the urinary and genital ducts, and in
front of them.
In many Teleostean fishes an air-bladder
underlies the vertebral
column, and is connected by an open pneumatic duct
with the dorsal wall of the oesophagus, or even with the stomach,
as in the Herring. In other Teleostei
, the air-bladder occupies
the same position, but is closed, the duct by which the
air-bladder is primitively connected with the alimentary canal
becoming obliterated. In a comparatively small number of
, the Pleuronectidae
the Sand-eel (Ammodytes
), the Loricarini
, and Symbranchii
and some members of other families-there is no air-bladder.
In those Teleostei
in which it is present, it may be divided into
two parts by a constriction; or it may be prolonged into diverticula; or retia mirabilia
may be developed in its walls.
Sometimes the air-bladder is brought into direct relation with
the membranous labyrinth, as in Myripristis
the Herring, Shad, and Anchovy-prolongations of the one organ
being separated from the other only by a membranous
fenestra in the wall of the skull. In the Siluroidei
, and in the Gymnotini
, the anterior
end of the air-bladder is connected with the membranous vestibule
by the intermediation of a series of bones attached to the
vertebral column, some of which are movable.
The vessels of the air-bladder are derived from, and empty
themselves into, those of the adjacent parts of the body, in
which respect, and in the dorsal position of the oesophageal
aperture of the pneumatic duct, this structure differs from a
The heart consists of a single auricle, receiving its blood
from a venous sinus; and of a single ventricle, separated by a
single row of valves from the bulbus aortoe
, which is not rhythmically
The cardiac aorta divides into trunks to form the branchial
arteries, which run upon the outer, or convex, side of the branchial
arches, and are distributed to the branchial filaments.
The blood is collected thence into a branchial vein, which also
lies on the convex side of the arch; and, increasing toward its
dorsal end, opens into one of the trunks of the original dorsal
aorta. Of these there are two, a right and a left, which pass
backward and meet in the trunk of the dorsal aorta under the
The anterior branchial vein gives off, at its dorsal termination,
a considerable carotid trunk, which passes forward under
the base of the skull; and this is united with its fellow by a
transverse branch-so that a complete arterial circle, the circulus
, is formed beneath the base of the skull. Below,
the anterior branchial vein gives off the hyoidean artery,
which ascends along the hyoidean arch, and very generally
terminates by one branch in the cephalic circle, and by another
enters a rete mirabile
, which lies in the inner side of the
hyomandibular bone, and sometimes has the form of a gill. This
is the pseudobranchia
. The branches of the rete mirabile
unite again into the ophthalmic artery, which pierces the sclerotic,
and breaks up into another rete mirabile
, the choroid
, before being finally distributed.
In the Lamprey, as has been seen, the respiratory organs
are pouches, the anterior and posterior walls of which are
raised into vascular folds. The walls of adjacent pouches are
distinct and but loosely connected together; and considerable
spaces of integument separate their rounded outer apertures.
In the ordinary Elasmobranchii
, the branchial pouches are
more flattened from before backward, and their outer apertures
are more slit-like. The integumentary spaces between the
slits are correspondingly narrower, and the adjacent walls of
successive pouches are more closely approximated, so that they
are divided only by sepia; but the vascular plaits of the surface
of the respiratory mucous membrane do not reach the
outer edges of these septa.
, the free edges of the septa are exceedingly
narrow, and the apices of the branchial processes extend outward
In the Sturgeon, the septum is not more than three-fourths
as long as the branchial processes, the apices of which are
The process of reduction is carried still further in the Teleostei-the septum
not attaining to more than one-third the
length of the branchial processes; and, as in the Ganoids,
each process is supported by an osseous or cartilaginous
have no functional hyoidean, or opercular,
gill; and, as a general rule, each of their four branchial arches
possesses a double series of branchial processes, making eight
in all. Not unfrequently (Cottus, Cyclopterus, Zeus,
number is reduced to seven; the fourth branchial arch having
only one series, the anterior. In this case, the gill-cleft, which
should lie between this arch and the fifth, is closed. Sometimes
there are only six series of branchial processes, the fourth
arch being devoid of any (e. g., Lophius, Diodon
). In Malthaea
the number is reduced to five, only the anterior series of
the third arch being developed; and in Amphipnous cuchia
only the second branchial arch possesses branchial filaments,
the first, third, and fourth, being devoid of them.
Many Teleostean fishes possess accessory respiratory organs.
These may take the form of arborescent appendages to
the upper ends of some of the branchial arches, as in Clarias,
, and Heterotis
; or, as in the Climbing Perch
) and its allies, the epipharyngeal bones may enlarge
and acquire a labyrinthic honeycombed structure, and support
a large surface of vascular mucous membrane; or, as in the Clupeoid
), an accessory gill may be developed
in a curved caecal prolongation of the branchial cavity. Finally,
in Saccobranchus singio
and in Amphipnous cuchia
membrane lining the branchial chamber is prolonged into sacs,
which lie at the sides of the body, and receive the blood from
the divisions of the cardiac aorta which supply the branchise,
while they return it into the dorsal aorta.
|Fig. 50. - Brain of tlie Pike, viewed
from above: A, the olfactory
nerves or lobes, and beneath
them the optic nerves; B, the
cerebral hemispheres; C, the
optic lobes; D, the cerebellum.
All these fishes (except Lutodeira
) are remarkable for their
power of sustaining life out of the water. Many inhabit the
marshes of hot countries, which become more or less desiccated
in the dry season.
The kidneys of Teleostean fishes receive a great part of
their blood from the caudal vein, which ramifies in them. They
vary greatly in length, sometimes extending along the whole
under-surface of the vertebral column, from the head to the
termination of the abdomen. The ureters pass into a urinary
bladder which opens behind the rectum.
The brain in the Teleostei
cerebral hemispheres, and, when
viewed from above, the thalamencophalon
is hidden by the approximation
to the hemispheres of the large
and hollow optic lobes of the mesencephalon,
which has a pair of inferior
enlargements, lobi inferiores
is a peculiarity about the structure. of
the optic lobes, which has given rise
to much diversity of interpretation of
the parts of the brain in osseous fishes.
The posterior wall of these lobes,
where it passes into the cerebellum, or
in the region which nearly answers
to the valve of Vieussens in mammals,
is thrown forward into a deep fold
which lies above the crura cerebri,
and divides the iter a tertio ad quartum
from the ventricle
of the optic lobes throughout almost
the whole extent of the latter. This
fold is the "fornix" of Gottsche. On
each side of it the floor of the ventricle of the optic lobes is
raised up into one or more eminences, which have the same
relation to the optic lobes as the corpora striata
have to the
The optic nerves simply cross one another, and form no
chiasma. The cerebellum is usually large.
The cephalic part of the sympathetic nerve is present, as
in the higher Vertebrata
Each of the nasal sacs usually opens externally by two
apertures. In some Gymnodonts a solid tentacle is said to
take the place of a nasal sac.
The eyes are abortive in the Blind-fish of the caves of Kentucky
). A fibrous band often passes
from the back of the orbit to the sclerotic, and represents the
cartilaginous pedicle of the Elasmobranchs. There is no nictitating membrane, but immovable external eyelids may be
developed. The choroidal gland, mentioned above, surrounds
the optic nerve between the sclerotic and the choroid. Very
generally, a falciform process
of the latter membrane traverses
the retina and vitreous humor to the crystalline lens. This
represents the pecten
of higher Vertebrata
. As in other fishes,
the lens is spheroidal, and the cornea flat. The sacculus of the
auditory organ contains large solid otoliths, which are usually
two in number - the larger, anterior one, is termed Sagitta
the smaller, posterior, Asteriscus
. There are always three
large semicircular canals.
The reproductive organs are either solid glands which burst
into the abdominal cavity, whence their reproductive elements
are conveyed away by abdominal pores; or, as is more usual,
they are hollow organs, and are continued backward into ducts
which open beside, or behind, the urinary aperture.
Some few Teleostei
are ovoviviparous (e. g., Zoarces viviparus
the eggs being retained in the interior of the ovary,
and hatched there. In the male Syngnathus
, and other Lophohranchii
integumentary folds of the abdomen grow down
and form a pouch, into which the eggs are received, and in
which they remain until they are hatched.
The young of osseous fishes are not known to undergo any
metamorphosis, nor are they provided with external gills, nor
The classification of the Teleostei
is not yet in a thoroughly
satisfactory state, and the following arrangement must be regarded
1. The Physostomi
.- This group contains the Siluroidei
, the Characini
, the Cyprinodontes
, the Salmonidoe
, the Esocini
, the Mormyri
, the Galaxice
, the Heteropygii
, the Muraenoidei, Symbranchii,
. The air-bladder is almost always
present, and, when it exists, has an open pneumatic duct. The
skin is either naked, or provided with bony plates, or cycloid
scales; the ventral fins, when present, are abdominal in position.
The fin-rays (except in the pectoral and dorsal fins of
) are all soft and jointed. The inferior pharyngeal
bones are always distinct.
In all other Teleostean fishes the air-bladder is either absent,
or devoid of an open pneumatic duct. Hence they are
termed, collectively, Physoclisti
2. The Anacanthini.
- The body has cycloid or ctenoid
scales, or is naked. The ventral fins, if present, are jugular in
position. The fin-rays are all articulated. The inferior pharyngeal
bones are distinct. (Ophidini
are the most aberrant of all Teleostean
fishes, on account of the disturbance in the bilateral symmetry
of the body, skull, and fins, to which reference has already
been made (p. 30).
3. The Acanthopteri
have generally ctenoid scales, thoracic
or jugular ventral fins, entire fin-rays in some of the fins, and
distmct inferior pharyngeal bones. The Percoidei, Cataphracti,
Sparoidei, Scicenoidei, Labyrinthici, Mugiloidei, Notacanthini,
Scomberoidei, Squamipennes, Taenioidei, Gobioidei,
Blennioidei, Pediculati, Theuthyes,
to this great group.
4. The Pharyngognathi
is the name given by Muller to a
somewhat artificial assemblage of fishes, the only common
characters of which are the anchylosis of the inferior pharyngeal
bones and the closed pneumatic duct. They have either
cycloid or ctenoid scales. The ventral fins may be abdominal
or thoracic. The anterior dorsal and ventral fin-rays may be
either unjointed, as in the Labroidei, Pomacentridae, Chromidae;
or articulated, as in the Scomberesoces
The two remaining groups are very peculiar; but I confess.
I do not see upon what ground they can be regarded as
of ordinal value.
5. The Lophobranchii
. - The body is covered with bony
plates. The ventral fins are almost always absent. The inferior
pharyngeal bones are distinct. The branchial processes
have a clavate form, being larger at the free than at the attached
ends, and are in this respect unlike those of any other
fishes. (Pegasidae, Syngnathidae.
6. The Plectognathi
. - The body is covered with plates or
spines. The ventral fins are absent or represented only by
spines. The inferior pharyngeal bones are distinct. The premaxillae
and, usually, the hyomandibular, are immovably united
with the skull-a character of rare occurrence among other
fishes. (Gymnodontidae, Ostraciontidae, Balistidae.
The greater number of Teleostei
are marine. No Anacanthini,
, and only one family of Pharyngognathi
), inhabit completely fresh
water. Comparatively few Acanthopteri
are fluviatile. On
the other hand, by far the greater number of the Physostomi
are, either temporarily or permanently, fresh-water fish.
If the Leptolepidae
(Thrissops, Leptolepis, Tharsis
Ganoids, the Teleostei
are not known before the Cretaceous
epoch, when both Physostomi
appearance, under forms, some of which (e. g., Beryx
generically identical with fish living at the present day.