SERIES PLECTOGNATHI
=THE Plectognaths.=—Derived directly from the _Acanthuridæ_, from which
they differ by progressive steps of degeneration, are the three
suborders of _Sclerodermi_, _Ostracodermi_, and _Gymnodontes_, forming
together the series or suborder of _Plectognathi_. As the members of
this group differ from one another more widely than the highest or most
generalized forms differ from the _Acanthuridæ_, we do not regard it as
a distinct order. The forms included in it differ from the _Acanthuridæ_
much as the swordfishes differ from ordinary mackerel. The
_Plectognathi_ (πλεϡτός, woven together; γνάθος, jaw) agree in the union
of the maxillary and premaxillary, in the union of the post-temporal
with the skull, in the great reduction of the gill-opening, and in the
elongation of the pelvic bones. All these characters in less degree are
shown in the _Squamipinnes_. We have also the reduction and final entire
loss of ventral fins, the reduction and loss of the spinous dorsal, the
compression and final partial or total fusion of the teeth of the upper
jaw, the specialization of the scales, which change from bony scutes
into a solid coat of mail on the one hand, and on the other are reduced
to thorns or prickles and are finally altogether lost. The number of
vertebræ is also progressively reduced until in the extreme forms the
caudal fin seems attached to the head, the body being apparently
wanting. Throughout the group poisonous alkaloids are developed in the
flesh. These may produce the violent disease known as ciguatera,
directly attacking the nervous system. See p. 182, vol. I.
The three suborders of plectognathous are easily recognized by external
characters. In the _Sclerodermi_ (σκλερός, hard; δέρμα, skin) the
spinous dorsal is present and the body is more or less distinctly scaly.
The teeth are separate and incisor-like and the form is compressed. In
the _Ostracodermi_ (ὀστράκος, a box; δέρμα, skin) there is no spinous
dorsal, the teeth are slender, and the body is inclosed in an immovable,
bony box. In the _Gymnodontes_ (γυμνός, naked; ὀδούς, tooth) the teeth
are fused into a beak like that of a turtle, either continuous or
divided by a median suture in each jaw, the spinous dorsal is lost, and
the body is covered with thorns or prickles or else is naked.
=The Scleroderms.=—The _Sclerodermi_ include three recent and one
extinct families. Of the recent forms, _Triacanthidæ_ is the most
primitive, having the ventral fins each represented by a stout spine and
the skin covered with small, rough scales. The dorsal has from four to
six stiff spines.
_Triacanthodes anomalus_ is found in Japan, _Hollardia hollardi_ in
Cuba. _Triacanthus brevirostris_, with the first spine very large, is
the common hornfish of the East Indies ranging northward to Japan.
[Illustration:
FIG. 345.—The Trigger-fish, _Balistes carolinensis_ Gmelin. New York.
]
=The Trigger-fishes: Balistidæ.=—The _Balistidæ_, or trigger-fishes,
have the body covered with large rough scales regularly arranged. The
first dorsal fin is composed of a short stout rough spine, with a
smaller one behind it and usually a third so placed that by touching it
the first spine may be set or released. This peculiarity gives the name
of trigger-fish as well as the older name of _Balistes_, or cross-bow
shooter. There are no ventral fins, the long pelvis ending in a single
blunt spine. The numerous species of trigger-fishes are large coarse
fishes of the tropical seas occasionally ranging northward. The center
of distribution is in the East Indies, where many of the species are
most fantastically marked. _Balistes carolinensis_, the leather-jacket,
or cucuyo, is found in the Mediterranean as also on the American coast.
_Balistes vetula_, the oldwife, oldwench, or cochino, marked with blue,
is common in the West Indies, as are several other species, as
_Canthidermis sufflamen_, the sobaco, and the jet-black _Melichthys
piceus_, the black oldwife, or galafata. Several species occur on the
Pacific Coast of Mexico, the Pez Puerco, _Balistes verres_, being
commonest. Still others are abundant about the Hawaiian Islands and
Japan. The genus _Balistapus_, having spinous plates on the tail,
contains the largest number of species, these being at the same time the
smallest in size and the most oddly colored. _Balistapus aculeatus_ and
_Balistapus undulatus_ are common through Polynesia to Japan. Most of
the tropical species of _Balistidæ_ are more or less poisonous, causing
ciguatera, the offensive alkaloids becoming weaker in the northern
species. _Melichthys radula_ abounds in Polynesia. In this species great
changes take place at death, the colors changing from blue and mottled
golden green to jet black. Other abundant Polynesian species are
_Xanthichthys lineopunctatus_, _Balistes vidua_, _Balistes bursa_, and
_Balistes flavomarginatus_.
[Illustration:
FIG. 346.—File-fish, _Osbeckia lævis_ (_scripta_). Wood's Hole, Mass.
]
[Illustration:
FIG. 347.—The Needle-bearing File-fish, _Amanses scopas_ of Samoa.
]
=The File-fishes: Monacanthidæ.=—Closely related to the _Balistidæ_ are
the _Monacanthidæ_, known as filefishes, or foolfishes. In these the
body is very lean and meager, the scales being reduced to shagreen-like
prickles. The ventral fins are replaced by a single movable or immovable
spine, which is often absent, and the first dorsal fin is reduced to a
single spine with sometimes a rudiment behind it. The species are in
general smaller than the _Balistidæ_ and usually but not always dull in
color. They have no economic value and are rarely used as food, the dry
flesh being bitter and offensive. The species are numerous in tropical
and temperate seas, although none are found in Europe. On our Atlantic
coast, _Stephanolepis hispidus_ and _Ceratacanthus schœpfi_ are common
species. In the West Indies are numerous others, _Osbeckia lævis_ and
_Alutera güntheriana_, largest in size, among the commonest. Both of
these are large fishes without ventral spine. _Monacanthus chinensis_,
with a great, drooping dewlap of skin behind the ventral spine, is found
on the coast of China. Of the numerous Japanese species, the most
abundant and largest is _Pseudomonacanthus modestus_, with deep-blue
fins and the ventral spine immovable. Another is _Stephanolepis
cirrhifer_, known as _Kawamuki_, or skin-peeler. _Alutera monoceros_,
and _Osbeckia scripta_, the unicorn fish, abound in the East Indies,
with numerous others of less size and note. In the male of the
Polynesian _Amanses scopas_ (Fig. 347) the tail is armed with a brush of
extraordinarily long needle-like spines.
In _Stephanolepis spilosomus_ the caudal fin is of a brilliant scarlet
color, contrasting with the usual dull colors of these fishes. In
_Oxymonacanthus longirostris_ the body is blue with orange checker-like
spots and the snout is produced in a long tube. About the islands of
Polynesia, filefishes are relatively few, but some of them are very
curious in form or color.
[Illustration:
FIG. 348.—Common File fish, _Stephanolepis hispidus_ (Linnæus).
Virginia.
]
=The Spinacanthidæ.=—In the extinct family _Spinacanthidæ_ the body is
elongate, high in front and tapering behind. The first dorsal has six or
seven spines, and there are rough spines in the pectoral. The teeth are
bluntly conical. _Spinacanthus blennioides_ and _S. imperalis_ are found
in the Eocene of Monte Bolca. These are probably the nearest to the
original ancestor among known scleroderms.
=The Trunkfishes: Ostraciidæ.=—The group _Ostracodermi_ contains the
single family of _Ostraciidæ_, the trunkfishes or cuckolds. In this
group, the body is enveloped in a bony box, made of six-sided scutes
connected by sutures, leaving only the jaws, fins and tail free. The
spinous dorsal fin is wholly wanting. There are no ventral fins, and the
outer fins are short and small. The trunkfishes live in shallow water in
the tropical seas. They are slow of motion, though often brightly
colored.
[Illustration:
FIG. 349.—Horned Trunkfish, Cowfish, or Cuckold, _Lactophrys
tricornis_ (Linnæus). Charleston, S. C.
]
[Illustration:
FIG. 350.—Horned Trunkfish, _Ostracion cornutum_ (Linnæus). East
Indies. (After Bleeker.)
]
[Illustration:
FIG. 351.—Spotted Trunkfish, _Lactophrys bicaudalis_ (Linnæus).
Cozumel Island, Yucatan.
]
[Illustration:
FIG. 352.—Spotted Trunkfish (face view), _Lactophrys bicaudalis_
(Linnæus).
]
[Illustration:
FIG. 353.—Spineless Trunkfish, _Lactophrys triqueter_ (Linnæus).
Tortugas.
]
Against most of their enemies they are protected by the bony case. The
species range from four inches to a foot in length, so far as known.
They are not poisonous, and are often baked in the shell. Three genera
are recognized: _Lactophrys_ with the _carapace_, three-angled;
_Ostracion_ with four angles; and _Aracana_, resembling _Ostracion_, but
with the carapace not closed behind the anal fin. In each of these
genera there is considerable minor variation due to the presence or
absence of spines on the bony shell. In some species, called cuckolds,
or cowfishes, long horns are developed over the eye. Others have spines
on some other part of the shield and some have no spines at all. No
species are found in Europe, and none on the Pacific coast of America.
The three-angled species, called _Lactophrys_, are native chiefly to the
West Indies, sometimes carried by currents to Guinea, and one is
described from Australia. _Lactophrys tricornis_ of the West Indies has
long horns over the eye; _Lactophrys trigonus_ has spines on the lower
parts only. _Lactophrys triqueter_ is without spines, and the fourth
American species, _Lactophrys bicaudalis_, is marked by large black
spots. The species of _Ostracion_ radiate from the East Indies. One of
them, _Ostracion gibbosum_, has a turret-like spine on the middle of the
back, causing the carapace to appear five-angled; _Ostracion diaphanum_
has short horns over the eye, and _Ostracion cornutum_ very long ones;
_Ostracion_ _immaculatus_, the common species of Japan, is without
spines; _Ostracion sebæ_ of Hawaii and Samoa is deep, rich blue with
spots of golden. _Aracana_ is also of East Indian origin; _Aracana
aculeata_, with numerous species, is common in Japan. A fossil species
of _Ostracion_ (_O. micrurum_) is known from the Eocene of Monte Bolca.
[Illustration:
FIG. 354.—Hornless Trunkfish, _Lactophrys trigonus_ (Linnæus).
Tortugas, Fla.
]
=The Gymnodontes.=—The group of _Gymnodontes_, having the teeth united
in a turtle-like beak, carry still further the degeneration of scales
and fins. There is no trace of spinous dorsal, or ventral. The scales
are reduced to thorns or prickles, or are lost altogether. All the
species have the habit of inflating themselves with air when disturbed,
thus floating, belly upward, on the surface of the water. Very few, and
these only northern species, are used as food, the flesh of the tropical
forms being generally poisonous, and that often in a higher degree than
any other fishes whatever.
[Illustration:
FIG. 355.—Skeleton of the Cowfish, _Lactophrys tricornis_ (Linnæus).
]
=The Triodontidæ.=—The most generalized family is that of the
_Triodontidæ_. These fishes approach the _Balistidæ_ in several regards,
having the body compressed and covered with rough scales. The teeth form
a single plate in the lower jaw, but are divided on the median line
above. The compressed, fan-like, ventral flap is greatly distensible.
_Triodon bursarius_, of the East Indies and northward to Japan, is the
sole species of the family.
[Illustration:
FIG. 356.—Silvery Puffer, _Lagocephalus lævigatus_ (Linnæus).
Virginia.
]
=The Globefishes: Tetraodontidæ.=—In the _Tetraodontidæ_ (globefishes,
or puffers), each jaw is divided by a median suture. The dorsal and anal
are short, and the ventrals are reduced in number, usually fifteen to
twenty (7 + 13 to 7 + 9). The walls of the belly are capable of
extraordinary distension, so that when inflated, the fish appears like a
globe with a beak and a short tail attached. The principal genus
_Spheroides_ contains a great variety of forms, forming a closely
intergrading series. In some of these the body is smooth, in others more
or less covered with prickles, usually three-rooted. In some the form is
elongate, the color silvery, and the side of the belly with a
conspicuous fold of skin. In these species, the caudal is lunate and the
other fins falcate, and with numerous rays. But these forms (called
_Lagocephalus_) pass by degrees into the short-bodied forms with small
rounded fins, and no clear line has yet been drawn separating the group
into genera. In these species each nostril has a double opening.
_Lagocephalus lagocephalus_, large and silvery, is found in Europe.
_Lagocephalus lævigatus_ replaces it on the Atlantic Coast of North
America. In Japan are numerous forms of this type, the venomous
_Lagocephalus sceleratus_ being one of the best known. Numerous other
Japanese species, _Spheroides xanthopterus_, _rubripes_, _pardalis_,
_ocellatus_, _vermiculatus_, _chrysops_, etc., mark the transition to
typical _Spheroides_. _Spheroides maculatus_ is common on our Atlantic
coast, the puffer, or swell-toad of the coastwise boys who tease it to
cause it to swell. _Spheroides spengleri_ and _S. testudineus_ abound in
the West Indies. _Spheroides politus_ on the west coast of Mexico.
[Illustration:
FIG. 357.—Puffer, inflated, _Spheroides spengleri_ (Bloch). Wood's
Hole, Mass.
]
[Illustration:
FIG. 358.—Puffer, _Spheroides maculatus_ (Schneider). Noank, Conn.
]
In _Tetraodon_ the nasal tentacle is without distinct opening, its tip
being merely spongy. The species of this genus are even more inflatable
and are often strikingly colored, the young sometimes having the belly
marked by concentric stripes of black which disappear with age.
_Tetraodon hispidus_ abounds in estuaries and shallow bays from Hawaii
to India. In Hawaii, it is regarded as the most poisonous of all fishes
(muki-muki) and it is said that its gall was once used to poison arrows.
_Tetraodon fahaka_ is a related species, the first known of the family.
It is found in the Nile. _Tetraodon lacrymatus_, black with white spots,
is common in Polynesia. _Tetraodon aërostaticus_, with black spots, is
frequently taken in Japan, and _Tetraodon setosus_ is frequent on the
west coast of Mexico. This species is subject to peculiar changes of
color. Normally dark brown, with paler spots, it is sometimes deep blue,
sometimes lemon-yellow and sometimes of mixed shades. Specimens showing
these traits were obtained about Clarion Island of the Revillagigedos.
No _Tetraodon_ occurs in the West Indies. _Colomesus psittacus_, a river
fish of the northern part of South America, resembles _Spheroides_, but
shows considerable difference in the skull.
[Illustration:
FIG. 359.—_Tetraodon meleagris_ (Lacépède). Riu Kiu Islands.
]
But few fossil _Tetraodontidæ_ have been recognized. These are referred
to _Tetraodon_. The earliest is _Tetraodon pygmæus_ from Monte Bolca.
The _Chonerhinidæ_ of the East Indies are globefishes having the dorsal
and anal fins very long, the vertebræ more numerous (12 + 17),
twenty-nine in number. _Chonerhinus naritus_ inhabits the rivers of
Sumatra and Java.
The little family of _Tropidichthyidæ_ is composed of small globefishes,
with a sharply-keeled back, and the nostrils almost, or quite, wanting.
The teeth are as in the _Tetraodontidæ_. The skeleton differs
considerably from that of _Spheroides_, apparently justifying their
separation as a family. The species are all very small, three to six
inches in length, and prettily colored. In the West Indies
_Tropidichthys rostratus_ is found. _Tropidichthys solandri_ abounds in
the South Seas, dull orange with blue spots. _Tropidichthys rivulatus_
is common in Japan and several ether species are found in Hawaii.
[Illustration:
FIG. 360.—Bristly Globefish, _Tetraodon setosus_ Rosa Smith. Clarion
Island, Mex.
]
Other species occur on the west coast of Mexico, in Polynesia, and in
the East Indies.
[Illustration:
FIG. 361.—Porcupine-fish, _Diodon hystrix_ (Linnæus). Tortugas
Islands.
]
=The Porcupine-fishes: Diodontidæ.=—In the remaining families of
_Gymnodontes_, there is no suture in either jaw, the teeth forming an
undivided beak. The _Diodontidæ_, or porcupine-fishes, have the body
spherical or squarish, and armed with sharp thorns, the bases of which
are so broad as to form a continuous coat of mail. In some of them, part
of the spines are movable, these being usually two-rooted; in others,
all are immovable and three-rooted. All are reputed poisonous,
especially in the equatorial seas.
In _Diodon_ the spines are very long, the anterior ones, at least,
movable. The common porcupine-fish, _Diodon hystrix_, is found in all
seas, and often in abundance. It is a sluggish fish, olive and spotted
with black. It reaches a length of two feet or more, and by its long
spines it is thoroughly protected from all enemies. A second species,
equally common, is the lesser porcupine-fish, _Diodon holacanthus_. In
this species, the frontal spines are longer than those behind the
pectoral, instead of the reverse, as in _Diodon hystrix_. Many species
of _Diodon_ are recorded from the Eocene, besides numerous species from
later deposits. One of these, as _Heptadiodon heptadiodon_ from the
Eocene of Italy, with the teeth subdivided, possibly represents a
distinct family. _Diodon erinaceus_ is found in the Eocene of Monte
Bolca and _Progymnodon hilgendorfi_ in the Eocene of Egypt.
[Illustration:
FIG. 362.—Rabbit-fish, _Chilomycterus schœpfi_ (Walbaum). Noank, Conn.
]
In the rabbit-fishes (_Chilomycterus_) the body is box-shaped, covered
with triangular spines, much shorter and broader at base than those of
_Diodon_. Numerous species are known.
_Chilomycterus schœpfi_ is the common rabbit-fish, or swell-toad of our
Atlantic coast, light green, prettily varied with black lines. The
larger, _Chilomycterus affinis_, with the pectoral fin spotted with
black, is widely diffused through the Pacific. It is rather common in
Japan, where it is the torabuku, or tiger puffer. It is found also in
Hawaii, and it is once recorded by Dr. Eigenmann from San Pedro,
California, and once by Snodgrass and Heller, from the Galapagos.
=The Head-fishes: Molidæ.=—The headfishes, or _Molidæ_, also called
sunfishes, have the body abbreviated behind so that the dorsal, anal,
and caudal fins seem to be attached to the posterior outline of the
head. This feature, constituting the so-called gephyrocercal tail is a
trait of specialized degradation.
[Illustration:
FIG. 363.—Headfish (adult), _Mola mola_ (Linnæus). Virginia.
]
_Mola mola_, the common head-fish or sunfish, is found occasionally in
all tropical and temperate seas. Its form is almost circular, having
been compared by Linnæus to a mill-wheel (mola), and its surface is
covered with a rough, leathery skin. It swims very lazily at the surface
of the water, its high dorsal often rising above the surface. It is
rarely used as food, though not known to be poisonous. The largest
example known to the writer was taken at Redondo Beach, California, by
Mr. Thomas Shooter, of Los Angeles. This specimen was 8 feet 2 inches in
length, and weighed 1200 pounds. Another, almost as large, was taken at
San Diego, in April, 1904. No difference has been noticed among
specimens from California, Cape Cod, Japan, and the Mediterranean. The
young, however, differ considerably from the adult, as might be expected
in a fish of such great size and extraordinary form. (See Figs. 109 and
110, Vol. I.)
Fragments named _Chelonopsis_, and doubtfully referred to _Mola_, are
found in the Pliocene of Belgium. Certain jaws of cretaceous age,
attributed to _Mola_, probably belong, according to Woodward, to a
turtle.
[Illustration:
FIG. 364.—The King of the Mackerel, _Ranzania makua_ Jenkins, from
Honolulu. (After Jenkins.)
]
In the genus _Ranzania_, the body is more elongate, twice as long as
deep, but as in _Mola_, the body appears as if bitten off and then
provided with a fringe of tail. The species are rarely taken. _Ranzania
truncata_ is found in the Mediterranean and once at Madeira. _Ranzania
makua_, known as the king of the mackerels about Hawaii, is beautifully
colored brown and silvery. This species has been taken once in Japan.
In Hawaii it is believed that all the Scombroid fishes are subject to
the rule of the makua and that they will disappear if this fish be
killed. By a similar superstition, _Regalecus glesne_ is "king of the
herrings" in Norway and about Cape Flattery, _Trachypterus rex
salmonorum_ is "king of the salmon."