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the anal fin furnished with three spines and numerous soft rays. In form, the
compressed body is either elevated or oblong, and the lateral line continuous. The
single dorsal fin has a spinous portion in front, and a scaly sheath along the base,
separated by a groove from the body-scales. Small teeth are present in the jaws,
but the palate is toothless. Generally not exceeding a pound in weight, these
fishes are confined to the temperate region of the North Pacific, where they are
much more numerous on the American than on the Asiatic side. While the
majority belong to the genus Ditrema, of which an example (D. argenteum) from
San Francisco is represented in the illustration, one species constitutes the genus
Heterocarpus, distinguished by the number of dorsal spines being from sixteen to
eighteen, instead of only from seven to eleven. All these fish produce living
young, which are contained in the sheath of the ovaries, instead of in the oviduct.




Chromids.




TKISTIIAM'S CHHOMID.

Although some members of the preceding family may occasional!,
enter rivers, the chromicls, family Chromididce, differ from all the othi
fish with united lower pharyngeals in being exclusively fresh-water forms. Tin
distribution is somewhat peculiar, and very similar to that of the lung-fish
(exclusive of the Australian form). Thus they are found in the rivers of Tropiea
America and Africa, together with Madagascar, Syria, and Palestine, one outlyin
genus occurring in India ; and it may be remarked that all the genera from
New World are distinct from those of the Old World. Mostly of comparative!
small size, although one species of the type genus from the Nile grows to a 1m
of about twenty inches, the chromids may be distinguished from all the other tlnvr
Families of the present group by the absence of false gills. The body, which is
somewhat variable in form, is generally covered with ctenoid scales, although in
some cases these may be cycloid; and the lateral line is more or less interrupted.







MAILED TUBE-MOUTHS.



423



In the single dorsal tin the spinous portion usually exceeds the soft in extent ; the
anal fin having three or more spines, and its rayed portion being similar to the
soft dorsal. The jaws are provided with small teeth, but the palate is smooth;
and the number of gills is four, In some species the teeth are lobate and the
intestines complicated by many foldings; these types being vegetable -feeders
while all the remainder are carnivorous. Among the best known representatives
of the typical genus Chromis is the so-called butti of the Nile (C. niloticus), which
is one of the largest members of the family ; while Tristram's chromid ((7. tristrami)
here figured is from salt and other lakes in the Sahara and Ashanti. As a genus,
Chromis is distinguished by its lobate teeth, the presence of only three spines in
the anal fin, and the scaly gill-cover ; and it therefore belongs to the vegetable-
feeding group. Nineteen existing genera have been described; and the family
ippears to be represented by one, or perhaps two extinct generic types from the
eniddle Eocene of Monte Bolca, in Italy.

THE TUFT-GILLED AND CoMB-GiLLED FISHES, Suborders

LOPHOBRANCHII AND PLECTOGNATHI.

The two small subordinal groups of fan-finned fishes now to be noticed
lave been generally placed after the soft -finned fishes, but from recent
investigations into their anatomy it appears more probable that they are highly
specialised types related to the spiny-finned group.

THE MAILED TUBE-MOUTHS, Family SOLENOSTOMATID^;,

A few small fishes from the Indian Ocean constituting the genus Solenostoma
the sole representatives of the first family of the suborder Lophobranchii ; the
listinctive features of that subordinal group being as follows. The body is
rested in a segmented bony dermal skeleton, and the bones of the gill-cover are
luced to a single plate. The gill-openings are small, and the gills themselves
isist of small, rounded tufts springing from the gill-arches; while the
iscular system is characterised by its very slight development. The simple air-
ladder, when present, resembles that of the spiny-finned group in being unpro-
'idcd with a duct communicating with the pharynx; and the prolonged muzzle
e rm mates in a small toothless mouth, in which the bones are arranged as in the
;roup last named. In the family under consideration the gill-openings are wide ;
he rays of the first of the two dorsal fins are not articulated ; and the whole of the
ther fins are well developed. The mailed tube-mouths take their title from the great
longation of the tube-like muzzle ; the compressed body having a very short tail,
iid, like the head, being covered with a thin skin, beneath which are the large
i>ony plates, marked with a radiate pattern. The soft dorsal and anal fins arise
rom boss-like elevations of the hinder part of the body ; the pelvic fins, which are
'laced close together in the same vertical line as the tall first dorsal, and have seven
ays, are separate from one another in the males, but in the opposite sex have their
Inner edges joined to the skin of the chest so as to form a pouch for the reception
if the eggs. The air-bladder is wanting. A female of the blue-finned species (8.



TUFT-GILLED GROUP.

cyanopteruni) is shown in the accompanying illustration; the range of this form
extending from the coast of Zanzibar to China and Ceram. The female takes the
whole charge, not only of the exceedingly minute eggs, but likewise of the newly-
hatched fry. Like the members of the next family these fishes generally swim in
a more or less nearly vertical position, the dorsal fin exerting the chief propelling
power. The family is represented by an extinct genus from the Italian Eocene.




BLUE-FINNED TCBE-MOUTH (nat. S1ZC).

THE PIPE-FISHES AND SEA-HORSES, Family SYNGNATHID^E.

From the members of the preceding family the pipe-fishes may be dis-
tinguished by the reduction of the gill-opening to a very small opening at the
superior hinder angle of the gill-cover, as well as by the single soft dorsal fin, and
the absence of the pelvic fins; some of the other fins being likewise wanting in
certain genera. Mainly marine, although frequently entering brackish, and more
rarely fresh waters, these strange fishes are to be found on the coasts of tropical
and temperate seas in such situations as, from the abundance of seaweed, offer
them sufficient shelter. They are naturally poor swimmers, and if carried away
from protective covert may be borne helplessly out to the open ocean by the action
of currents. Unlike the tube-mouths, the males take charge of the eggs ;u
young, being often provided with a pouch formed by a fold of skin arising fi
each side of the body and tail, and joined together in the middle line; in the
horses this pouch being completely closed, save for a small aperture in froi
In this receptacle the eggs are deposited, and remain there till hatched. Tl
typical genus, as well as Siphonostoma, is represented in a fossil state in tl
middle Eocene of Monte Bolca, where there likewise occurs an extinct gem
of sea-horses. Including several genera, the pipe-fishes are characterised
the absence of prehensile power in the tail, which generally terminates
a fin. In the typical genus Syngnatkus, as represented by the great pipe-f
(S. acus), shown in our illustration, the body is marked with more or less distil
longitudinal ridges, among which the one down the back is not continuous wit
that on the tail. The pectorals are well developed, the caudal present, and the
dorsal fin placed nearly or exactly above the vent. In the males the pouch
fully developed, and of the type described above. The great pipe-fish is
common species in European seas, extending westwards across the Atlantic



PIPE-FISHES AND SEA-HORSES.



425



iouth wards to the Cape, and grows to a length of a foot and a half. As an
Example of a second genus, we may mention the deep-nosed pipe-fish (S. typhle),
>f the British seas, distinguished by the upper ridge on the tail being continuous
vith the lateral line, but not with the dorsal ridge. In the tropical genus
Voryichthys, as in some others, we find that the eggs are only glued to the skin
jkf a broad groove on the under surface of the males, instead of being protected by
i', closed pouch. The slender straight-nosed pipe-fish {Neropliis ophidium), which
aay not unfrequently be seen served up among a dish of whitebait, is a British
xample of a fourth genus, in which not only is there no pouch on the under




lurface of the males, but the body is rounded and nearly smooth, and the caudal
in either rudimentaiy or wanting. All the pipe-fishes are carnivorous in their
[iet ; and it is stated that in those species provided with a pouch, the fry will
jturn to this for shelter till a considerable time after birth. The pipe-fishes
rim about slowly in a very peculiar manner, more generally vertically or in an
iclined position than horizontally, contorting their bodies into every conceivable
lind of posture, and poking their long snouts inquisitively into bunches of sea-
] in their search for food.

The prehensile structure of the tail is the chief difference between sea-
)rses and pipe-fish, although in all the existing representatives of the former
roup there is no caudal fin. The sea-horses are divided into several genera, of



426



TUFT-GILLED GROUP.



which the typical one is best known by the short-snouted sea-horse (Hippocampus
antiquorum), ranging from the Atlantic and Mediterranean to Australia, and occa-
sionally found in the British seas. In this genus the body is more or less com-
pressed and deep, with its investing bony shields raised into tubercles or spines
of variable length ; while the back of the head is compressed into a crest, terminat-
ing in a well-marked knob. Small pectoral fins are present, and the males have
a pouch beneath the tail, with its aperture near the vent, in which to carry the
eggs. The curious resemblance presented by the heads of these fishes to that of
a horse has obviously given rise to their popular name. They are represented






FUCUS-LIKE SEA-HOIISE ( liat. size).

by about a score of species. A remarkable instance of resemblance to their nati
surroundings is afforded by the three representatives of an Australian genus
sea-horses, one of which (Phyllopteryx eques) is shown in the accompai
illustration. In these fishes the body may be either compressed or as broad as dt
some or all of its smooth bony plates being furnished with long spine-like pi
projecting from its edges, and many of these terminating in irregular Ira Hi
appendages. There are a pair of spines on the muzzle, and others above the
pectoral fins are present ; and the tail is about equal in length to the body,
the absence of a pouch, the eggs are embedded in soft membranous skin on
under surface of the tail. These sea-horses closely resemble the colour of tin-
weeds to which they attach themselves, while the filamentous appendages of tl



FILE- FISHES AND COFFER-FISHES. 427

)|)ines appear as if they were actually a part of the vegetable growth. These
Ipecies are of relatively large size, attaining a length of as much as a foot.

FILE-FISHES AND COFFER-FISHES, Family EALISTIDJE.

With the file-fishes and their allies we come to the first of the two families
instituting the suborder Plectognathi, of which the following are the distinctive
aaracters. In the head the bones are completely ossified, while in the rest of the
iceleton they are incompletely hardened ; the number of vertebrae being few.
me small gill-openings are situated in front of the pectoral fins, and the gills
piemselves are pectinate ; the mouth being narrow, with some of the bones of the
ipper jaw united, and in certain cases both jaws prolonged to form a beak. There
i generally a single soft-rayed dorsal fin, placed far back on the body, and situated
jhmediately above the anal ; and there may be remnants of a spinous dorsal ;
*hile the pelvic fins, when retained at all, take the form of simple spines. The
Kin may be either entirely naked, covered with rough scales, invested in a
Complete cuirass of plates composed of true bone, or dotted over with bony spines,
'here is no duct connecting the air-bladder with the pharynx. As a family, the
ie-fishes and their allies are specially distinguished by the presence of a small
umber of distinct teeth in the jaws. Their bodies are either compressed or
agulated, with a somewhat produced muzzle ; more or less distinct vestiges of a
oinous dorsal and pelvic fins generally occur ; and the skin may be either rough
<: spiny, or the whole body invested in a bony cuirass. These fishes, which are
(' medium size, range over all tropical and temperate seas, although more numerous
i the former than in the latter, and may be divided into three subfamilies, in each
(' which we notice an example. Extinct generic types date from the period of
] le lower Eocene, while the file-fishes themselves are recorded from the middle
ocene of Monte Bolca.

The first subfamily is typically represented by Triacanthus brevirostris, from

lie Indian Ocean, the other genera being from the Australian seas. The special

aaracters of the group are to be found in the compressed form of the body, and

i s covering of rough, scale-like plates, as well as in the presence of a pair of strong

>ines representing the pelvic fins ; the type genus being distinguished by having

lloni four to six spines in the spinous dorsal fin. The typical file-fishes (Batistes)

long to a group of three genera in which the body is compressed, and covered
fcther with a rough skin or movable scale-like plates ; and the pelvic fins are either
panting or represented merely by a single median swelling on the abdomen. These
phes are distributed over all tropical and subtropical seas ; the first two genera
deluding a very large number of species. Whereas in the typical genus there are
iiree spines to the dorsal fin, and the chin is devoid of a barbel, Monacantkus
IjfFers in the reduction of the dorsal spines to two or one, and Anacanthus, which
jhs a single dorsal spine, is distinguished from both the others by the barbel on the
min. In many districts the flesh of these fishes, if eaten, gives rise to symptoms

most acute poisoning. Many of the species are beautifully ornamented with sym-
tietrical markings ; and while the majority are of small size, some attain as much as
couple of feet in length. Of the members of the typical genus Dr. Glinther writes



428 COMB-GILLED GROUP.

that, " both jaws are armed with eight strong incisor-like and obliquely truncated
teeth, by means of which these fishes are enabled to break off pieces of the corals
on which they feed, or to chisel a hole into the hard shells of molluscs, in order
to extract the soft parts. They destroy an immense number of molluscs, thus
becoming most injurious to the pearl-fisheries. The first of their three dorsal
spines is very strong, roughened in front like a file, and hollowed out behind to
receive the second much smaller spine, which, besides, has a projection in front at
its base, fitting into a notch of the first. Thus these two spines can only be ra
or depressed simultaneously, and the first cannot be forced down unless the ser
lias been previously depressed. The latter has been compared to a trigger, hei
second name trigger-fish has been given to these fishes." Two Atlantic sp<
of the genus are now and then met with on the British coasts.

The box-like coffer-fishes (Ostracion), of which there are rather more than
a score of species from the tropical and subtropical seas, alone represent the
third and last subfamily, and are easily recognised by the enclosure of the
angulated body in a complete cuirass formed of six-sided bony plates with their
edges in juxtaposition, thus forming a mosaic-like pattern. Both the spinous
dorsal and the pelvic fins are wanting, although their position may be indicated
by prominences. In the whole backbone there are but fourteen vertebra, of,
which the last five are very short, while those in the front of the series arej
much elongated ; and the ribs are entirely wanting. In some of the species the j
cuirass is marked by three, and in others by four or even five ridges; but in >
cases it is armed with long spines, which vary in length according to the age of
their owner. A species (0. qucidricornis) is figured in the coloured Plate.

THE GLOBE-FISHES AND SUN-FISHES, Family DIODONTILJE.

Unlike as they are in external appearance, the spine-clad globe-fishes ands
the huge flattened sun -fishes are referred to a single family, distinguish^
from the last by the bones of the jaws being confluent and modified into ,
cutting beak, which may or may not have a median suture, the dentition taking
the form of dental plates composed of thin parallel layers. The body is more or
shortened ; a spinous dorsal, anal, caudal, and pectoral fins are developed, but
pelvics are wanting. The external covering may take the form either of a nmn
of small or large spines, or of plates; and the air-bladder may be either pivsrn
absent. Inhabitants of tropical and subtropical seas, with the exception of a fe\\
found in the fresh waters of the same regions, the members of this family an
mostly small or medium-sized forms, although this is by no means the case witl
the sun-fishes. In many of them the flesh is of a highly poisonous nature, at
during certain seasons of the year. Like the preceding, the present family
be divided into three groups or subfamilies, the first of which is represented o
by the sac-fish (Triodon bwnariue) of the Indian seas, which takes its name f
the sac formed by the dilatable skin of the abdomen ; this sac being supported
the pelvic bone, and tilled with air at the \\ill of t he lish, although its lo\vei- po
consists merely of a flap of skin into which no air can enter. The dental p
of the upper jaw is divided by a median suture, while that of the lower ja



;iii:







GLOBE FISH AND COFFER FiSH.




GLOBE-FISHES.

mtinuous. The elongate tail terminates in a forked fin ; and the body is invested
ith spiny bony plates, which do not overlap one another. The single species, which
may attain a length of 20 inches, ranges over the Indian and Malayan seas, and is of
a general brown colour, with a spot of variable colour on the sac, and the fins yellow.
be Fishes Tne essen tial characteristics of the globe-fishes, which form the

second subfamily, are that the tail and its fin are distinct and well
eveloped, and that a portion of the oesophagus is highly distensible and capable of
ing inflated with air. All the globe-fishes, or, as they are sometimes called, sea-
edgehogs, are easily recognised by the short and cylindrical or rounded form of
e body ; which is generally covered with a scaleless skin bearing a number of
iries of variable size. When these spines are of large size, they are spread uniformly
er the whole body, but when small they are partial in their distribution. These
shes are divided into two groups, according to the nature of the dental plates. In
the first, or small-spined group, as typified by the genus Tetrodon,o which a
cies is represented in the lower figure of the coloured Plate, the dental plate of
ach jaw is divided by a median suture, and the spines are frequently very small,
d may be even altogether absent; many of the species being very brilliantly
iloured. One member of the genus inhabits the rivers of Brazil, and A second
those of West Africa and the Nile, while a small form is found in the brackish-
water estuaries of India. According to Day, the flesh of some of the species is
poisonous, while that of other kinds is eaten by the Andamanese and Burmese.
In the second group, of which the porcupine globe-fish (Diodon liystrix) is shown
in the lower figure of the coloured illustration, the dental plates in the jaws are
undivided, and the spines are large and frequently erectile. In addition to the

t divided dental plates on the edge of the jaws, in the members of this group
3re is another crushing plate in the middle of the palate, opposed by a similar
one in a corresponding position in the lower jaw ; these plates being divided by a
median suture, and from their laminated structure forming most admirable
triturating instruments. The porcupine globe-fish, which may measure fully a
couple of feet in length, is distributed over both the Atlantic and Indo-Pacific
Oceans, where it is accompanied by the smaller spotted globe-fish (D. maculatus).
Fossil diodons have been discovered in the Miocene strata of Malta and Sicily, as
well as in the middle Eocene of Monte Bolca, and in other Eocene beds on the
coasts of Algeria and Arakan ; while an extinct genus has also been recorded from
the Italian Eocene. In their normal state the globe-fishes have rather elongated
cylindrical bodies, but they are able to assume a globular form by swallowing air,
which passes into the oesophagus and blows out the whole animal like a balloon,
with the spines standing out at right angles from the tense skin. In this condition
the fish naturally floats back-downwards, and it is then driven to and fro on the
ocean-surface by waves and currents in a perfectly helpless condition ; although
the bristling spines render it perfectly safe from all attack. The distention is,
therefore, evidently for the purpose of defence ; and it has been suggested that
when swimming below the surface these fishes may inflate themselves in a similar
manner by swallowing water instead- of air. When desirous of returning to its
normal condition, the fish expels the air from the oesophagus through the mouth
and gill-openings ; a loud, hissing noise being produced by the expulsion.






430 SOFT-FIN NED GROUP.

The gigantic sun-fishes (Orthagafiicua), which are pelagic forms
distributed throughout the whole of the temperate and tropical seas,
alone represent the third subfamily, and are distinguished by the extremely short
and truncated tail, the confluence of all the median fins, and the short and highly
compressed body, the dental plates of the jaws being undivided. The skin is
either rough or smoothly tesselated, and incapable of distention with air; there
are no pelvic fins ; the air-bladder is wanting ; and there is an accessory opercular
gill. As in the globe-fishes, there are no pelvic bones in the skeleton, and the
vertebral column is remarkable for its extreme shortness, there being only
seventeen segments in the whole series, of which seven belong to the tail. In all
the members of the suborder the spinal cord is noticeable for its shortness ; but in
the sun-fishes this abbreviation has been carried to such an extent that the whole
cord is little more than a conical backward appendage of the brain. The creatures
considered to be very young sun-fish are utterly unlike the adult form, having
an enormous eye, and the head and body armed with a number of large spine-like
projections. The caudal fin is not developed till much later than the dorsal and
anal, which in the adult are very short, of great height, and placed opposite to one
another at the hinder end of the body. The common sun-fish (0. mom), which
has a rough, finely granulated skin, attains very large dimensions, an example
caught off the coast of Dorsetshire in 1846 measuring 7| feet in length.

Far rarer is the oblong sun-fish (0. truncatus), which is, indeed, one of the
scarcest objects in museums. It is readily distinguished by its smooth, tesselated
skin, and the more elongated form of the body ; the entire length being nearly
three times the breadth. An example of this fish, weighing 500 Ibs., was taken in
Plymouth Sound in the year 1734. Both species appear to feed on small pelagic
crustaceans. In a fossil state sun-fishes have been recorded from strata of lower
Miocene or upper Eocene age in Belgium.

THE SOFT-FINNED FISHES, Suborder Anacanthini.

This suborder, which includes the important families of the flat-fish and cods,
is characterised by the median and pelvic fins being entirely composed of soft
jointed rays ; the pelvic fins, if present, being either jugular or thoracic in position ;
and the air-bladder, when developed, having no duct communicating with the
oesophagus. It should, however, be mentioned, that a fresh- water Australian fish
(Gadopsis) forms an exception as regards the structure of its fins, having spines
in the anterior portion of both the anal and dorsal. The suborder is divided into
two sections, according to whether the head and body are symmetrical or distorted,
the first representatives of the former section being



Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 45 of 62)