Teleosts in possessing a rudiment of a conus arteriosus to the heart,
provided with two rows of valvules.[642] Its single species inhabits all
the warm and tropical seas. Prof. Gilbert has ascertained that the young
pass through a metamorphosis, analogous to that of the Eels. The
"Leptocephalid" described as _Esunculus_ by Kaup is probably a larval
_Albula_.
[Illustration: FIG. 328.—Larva of _Albula conorhynchus_. (After Gilbert.)]
The deep-sea Japanese _Pterothrissus_ (_Bathythrissa_) must be placed in
this family; its skeleton is very similar to that of _Albula_. It differs
in the elongate dorsal fin, in the presence of small teeth on the maxillary
bone, and in the small number of branchiostegal rays (6 instead of 12 to
14).
{549}_Albula_ is represented in the Eocene (London Clay and Bruxellian);
and the Cretaceous _Istieus_ and _Anogmius_ are believed to be possibly
related to _Pterothrissus_. Four Cretaceous types (_Plethodus_,
_Thryptodus_, _Syntegmodus_, and _Ancylostylus_) are referred with doubt to
the Albulidae.
FAM. 7. MORMYRIDAE.—Margin of the upper jaw formed by the single
praemaxillary and the maxillaries, the latter articulated above the former
to the ethmoid. Parietal bones separating the supraoccipital from the
frontals; a large hole on each side of the skull, between the squamosal,
the epiotic, and the opisthotic, covered by a large, thin, bony plate (the
supratemporal), which may extend over a part of the parietal; symplectic
absent; suboperculum small and hidden under the operculum, or absent;
interoperculum well developed. Basis cranii simple. No pharyngeal teeth.
Opercular bones hidden under the skin; gill-clefts narrow. Anterior ribs
sessile; epineurals, no epipleurals. Pectorals directed upwards. Ventrals
with 6 or 7 rays. Air-bladder communicating with the ear.
[Illustration: FIG. 329.—_Mormyrus caballus_. ⅕ nat. size.]
Curious-looking Fishes, very variable in the form of the head and body and
in the extent of the fins. Mouth often very small; teeth in jaws usually
few; teeth usually present on the parasphenoid, working against a similar
patch on the glossohyal; eye covered over by skin, sometimes very
indistinct; scales small, cycloid; branchiostegal rays 4 to 8. The dorsal
and anal fins may be nearly equally developed (_Genyomyrus_,
_Gnathonemus_); or the former (_Mormyrus_) or the latter (_Hyperopisus_)
are several times the longer. _Gymnarchus_, Eel-shaped, apodal, and
deprived of the caudal fin, lacks the anal fin, the dorsal extending over
the whole extent of the body. Some species of _Mormyrops_ show how a form
{550}like _Gymnarchus_ may have been evolved out of a more typically-formed
Fish. Nothing is more striking than the variation in shape of the snout
within one and the same genus, and the names given to some of the species
(_ovis_, _caballus_, _elephas_, _tamandua_, _numenius_, _ibis_) are
suggestive of resemblances with the heads of various animals.
[Illustration: FIG. 330.—Head of _Gnathonemus curvirostris_.]
[Illustration: FIG. 331.—Head of _Gnathonemus numenius_.]
The Mormyrids are highly remarkable for the enormous development of the
brain, the weight of which equals 1/52 to 1/82 of the total, a thing
unparalleled among lower Vertebrates; and for the problematic organ which
surmounts it; also as being among the few Fishes in which an electric organ
has been discovered. The organ, situated on each side of the caudal region,
is derived from the muscular system and is of feeble power, as ascertained
by Babuchin and by Fritsch; it was long considered as "pseudo-electric."
The natural affinities of this family appear to be with the Albulidae, and
there is nothing to justify the term "Nilhechte" (Nile-pike) which has been
bestowed on them by German {551}authors. Ninety-three species are known
from the fresh waters of Africa north of the Tropic of Capricorn, and may
be referred to two sub-families and ten genera[643]:—
(i.) MORMYRINAE, with teeth on the parasphenoid and tongue, with ventral,
anal, and caudal fins, and a simple air-bladder; vertebrae 37 to 64;
peculiar (Gemmingerian) linear bones, without known homologues, along each
side of the tail, above and beneath the electric organ; scapular foramen in
the scapula, or between the scapula and the coracoid. _Mormyrops,
Petrocephalus, Isichthys, Marcusenius, Stomatorhinus, Myomyrus,
Gnathonemus, Genyomyrus, Mormyrus_.
(ii.) GYMNARCHINAE, without teeth on the parasphenoid and tongue, without
ventral, anal, or caudal fins, and with a cellular air-bladder; vertebrae
about 120; Gemmingerian bones absent; scapular foramen in the coracoid.
_Gymnarchus_.
Fossil Mormyrids are unknown.
Venerated by the ancient Egyptians, the Mormyrs of the Nile are frequently
represented on hieroglyphics and mural paintings as well as in bronze
models. Very little is known of the habits of these Fishes. Prof. G.
Fritsch, of Berlin, during his stay in Egypt for the purpose of
experimenting on electric Fishes, observed that they perish very rapidly
when removed from the river, and he had the greatest difficulty in keeping
some alive in an aquarium for two or three days. The species with
comparatively large mouths (_Mormyrops_, _Gymnarchus_) feed principally on
fishes and crustaceans, the others on tiny animals and vegetable and more
or less decomposed matter. Delhez, on the Congo, found that many are
attracted to the borders of the river in the neighbourhood of human
dwellings, where they feed on the refuse thrown into the water. It is
probable that the species with a rostrum use it to procure small prey
hidden between stones or buried in the mud, and that the fleshy mental
appendage with which many are provided is a tactile organ compensating the
imperfection of the vision in the search for food. A small Mormyrid from
the Congo (_Stomatorhinus microps_) has the eyes so much reduced and the
skin so feebly pigmented as to convey the impression of a cave Fish. Until
quite recently, absolutely nothing was known {552}of the breeding habits
and development in this important family. To the late J. S. Budgett we owe
some very interesting observations made in the Gambia on _Gymnarchus
niloticus_.[644] The Fish makes a floating nest, emerging on three sides,
over which the male keeps a fierce watch; the recently-hatched larvae are
remarkable for the enormous size of the yolk-sac, which hangs down, acting
as a sort of anchor, and for the presence of long external branchial
filaments, as in Selachian embryos. The Fish propels itself through the
water entirely by the action of its dorsal fin, forwards and backwards with
equal facility; when swimming rapidly backwards, it may be seen to use the
end of its tail as a feeler to guide the way. Budgett has also identified,
with some doubt, the eggs of _Hyperopisus bebe_, out of which emerged
embryos not unlike those of some tailless Batrachians, which hung suspended
to rootlets of grass in swamps by means of threads of viscid mucus secreted
from glands on the top of the head.
[Illustration: FIG. 332.—_Gymnarchus niloticus_. ¼ nat. size.]
FAM. 8. HYODONTIDAE.—Margin of the upper jaw formed by the praemaxillaries
and the maxillaries, the latter the more developed and firmly united to the
end of the former. Parietal bones separating the supraoccipital from the
frontals; a large hole on each side of the skull, between the parietal, the
squamosal, and the epiotic (paroccipital), closed by a large, thin, bony
plate (the supratemporal), which extends over the greater part of the
parietal; suboperculum and interoperculum small, the latter partly hidden
below the praeoperculum. Basis cranii double. Jaws, palatines, pterygoids,
vomer, parasphenoid, and glossohyal toothed; no pharyngeal teeth. Ribs
sessile, inserted above and behind well-developed parapophyses; epineurals,
no epipleurals. {553}Pectorals low down, folding like the ventrals.
Post-temporal forked; the upper branch attached to the epiotic, the lower
to the squamosal; no post-clavicle; coracoids forming together a ventral
keel; scapular foramen between scapula and clavicle; pterygials well
developed, three in contact with coracoid. Ventrals with 7 rays.
Branchiostegal rays in moderate number (8 to 10). Air-bladder communicating
with the ear. No oviducts, the eggs falling into the abdominal cavity
before exclusion.
[Illustration: FIG. 333.—Upper (A) and posterior (B) views of skull and
pectoral arch of _Hyodon alosoides_ (the supratemporal removed on the left
side). _bo_, Basioccipital; _cl_, clavicle; _cor_, coracoid; _eo_,
exoccipital; _eot_, epiotic; _eth_, ethmoid; _f_, frontal; _m_, maxilla;
_mcor_, mesocoracoid; _n_, nasal; _oo_, opisthotic; _p_, parietal; _pcl_,
postclavicle; _pm_, praemaxilla; _por_, praeorbital; _ptf_, postfrontal;
_ptr_, pterygials; _ptte_, post-temporal; _scl_, supraclavicle; _so_,
supraoccipital; _sor_, suborbital; _sq_, squamosal; _ste_, supratemporal.]
Elongate, compressed, silvery Fishes, covered with moderate-sized cycloid
scales; head naked; mouth large, with strong dentition; gill-openings wide;
dorsal fin short, posterior to the ventrals; anal rather elongate; caudal
well developed, forked.
A single genus (_Hyodon_) with three species (Moon-Eyes of the Americans),
all reaching the length of about a foot, inhabiting the fresh waters of
North America east of the Rocky Mountains.
{554}FAM. 9. NOTOPTERIDAE. The Fishes which form this family may be
regarded as an eccentric modification of a type very similar to the
preceding, with which they agree in most osteological features as well as
in the dentition, in the connexion between the air-bladder and the ear, and
in the absence of oviducts. They differ in the absence of the lid-like
supratemporal, the hole which it covers in _Hyodon_ being here bordered by
the post-frontal and the squamosal (fused with the opisthotic), sometimes
also by the epiotic, in the absence of the suboperculum, in the absence or
incomplete ossification of the upper branch of the post-temporal (the lower
articulating with the opisthotic), and in the presence of accessory bones
(named adpleurals) attached to or fused with the distal extremity of the
anterior ribs, which they prolong to the mid-ventral line, where they are
embraced by dermal ossifications forming a doubly serrated crest.
[Illustration: FIG. 334.—_Notopterus afer_, skeleton, with outline of soft
parts. ⅔ nat. size.]
The bones of the head are cavernous, the mouth is large; the anterior
nostril is produced into a tentacle. The body is very strongly compressed,
with very short precaudal region, attenuate behind; the ventral fins are
much reduced or absent; the dorsal is short or absent, {555}and the anal is
much elongate and confluent with the caudal, which may be regarded as
aborted. The scapular foramen is entirely in the scapula. The air-bladder
is very large, with several divisions, forked in front and behind, and
prolonged along each side of the caudal region; its extraordinary condition
has been described by Bridge.[645]
These Fishes live in marshes and lakes, fresh-water or brackish, and feed
on worms and insects. Nothing is known of their breeding habits and
development.
Two genera: _Notopterus_, with a dorsal fin and 6 to 9 branchiostegal
rays—three species from India, Burma, and the Malay region, and one from
West Africa; _Xenomystus_, without dorsal fin and with only 3
branchiostegal rays, the unique species inhabiting the White Nile and West
Africa. Remains of _Notopterus_ have been found in the marl slates
(Tertiary) of Padang, Sumatra. The largest species, the Indian _N.
chitala_, attains 4 feet in length; its flesh is said to be uncommonly rich
and well flavoured, but a strong prejudice exists against it, owing to the
Fish being supposed to live on human carcases.
FAM. 10. OSTEOGLOSSIDAE.—Margin of the upper jaw formed by the
praemaxillaries and the maxillaries, the latter the more developed and
firmly attached to the end of the former. Parietal bones separating the
supraoccipital from the frontals; suboperculum much reduced, and entirely
or partially concealed under the praeoperculum. Basis cranii simple. Teeth
in jaws, and on pterygoid and hyoid bones; no pharyngeal teeth. Head
scaleless, the thin skin confluent with the bones; body covered with large
bony scales, composed of pieces like mosaic. Ribs inserted on the strong
parapophyses; epineurals, no epipleurals. Pectoral fins low down.
Post-temporal forked, the upper branch attached to the epiotic, the lower
to the squamosal; post-clavicle present; scapular foramen in scapula;
pterygials well developed, only one in contact with coracoid. Dorsal and
anal fins originating behind the ventrals; latter with 5 or 6 rays. No
oviducts, the eggs falling into the abdominal cavity before exclusion (at
least in _Heterotis_, as observed by Budgett).
This family is represented at the present day by five species, referred to
four genera; thus characterised:—
{556}[Illustration: FIG. 335.—Principal forms of Osteoglossids. A,
_Dapedoglossus testis_ (restoration); B, _Scleropages leichardti_; C,
_Osteoglossum bicirrhosum_; D, _Arapaima gigas_; E, _Heterotis niloticus_.
All much reduced.]
{557}_Scleropages_.—Mouth large; vomer, palatines, pterygoids, and
glossohyal toothed; mandibular barbels; branchiostegal rays 15 to 17; body
compressed, with trenchant abdomen; coracoids forming a ventral keel;
dorsal fin short; ventral fins nearly equally distant from end of snout and
caudal fin; vertebrae 29 to 31 + 30; air-bladder not cellular. One species
from the northern parts of Australia, and one from Sumatra, Banka, and
Borneo.
_Osteoglossum_.—Mouth large; vomer, palatines, pterygoids, and glossohyal
toothed; mandibular barbels; branchiostegal rays 10; body compressed, with
trenchant abdomen; coracoids forming a ventral keel; dorsal fin long;
ventral fins nearly twice as far from the caudal as from the end of the
snout; vertebrae 28 + 59; air-bladder not cellular.—South America (Guianas,
Brazil).
_Arapaima_.—Mouth rather large; vomer, palatines, pterygoids, and
glossohyal toothed; branchiostegal rays 16; belly rounded; dorsal fin
rather long; ventral fins equidistant from head and caudal fin; vertebrae
36 to 38 + 41 to 42; air-bladder cellular.—South America (Guianas, Brazil).
_Heterotis_.—Mouth moderate; branchiostegal rays 7; belly rounded; dorsal
fin rather long; ventral fins nearer end of snout than caudal fin;
vertebrae 27 + 42 to 43; air-bladder cellular; fourth branchial arch with
an accessory breathing-organ. Africa (Nile, Senegal, Gambia, Niger).
_Dapedoglossus_, from the Eocene of Wyoming, appears to be nearest to
_Scleropages_, and _Brychaetus_, from the Eocene (London Clay) of Sheppey,
Kent, to _Arapaima_, so far as the state of preservation of these fossils
enables us to form an opinion.
[Illustration: FIG. 336.—Distribution of the Osteoglossids.]
Dr. Günther has directed attention to the remarkable {558}coincidence of
the geographical distribution of this family and the Dipneusti, although,
however, the latter are not known to be represented in the Malay
Archipelago. "Not only," he adds, "are the corresponding species found
within the same region, but also in the same river systems; and although
such a connexion may and must be partly due to a similarity of habit, yet
the identity of this singular distribution is so striking that it can only
be accounted for by assuming that the Osteoglossidae are one of the
earliest Teleosteous types which have been contemporaries of and have
accompanied the present Dipnoi since or even before the beginning of the
Tertiary epoch."
The Queensland species of _Scleropages_ (_S. leichardti_) is known to the
settlers by the name of Barramunda, which has also been applied to
_Neoceratodus_. _Arapaima gigas_ is one of the largest fresh-water Fishes
known, exceeding a length of 15 feet and a weight of 400 pounds. Its flesh
is much valued. Sir R. Schomburgh has observed that the mother protects the
young, who, for some time after their birth, always swim in front of her. A
similar observation has been made in the Gambia on _Heterotis niloticus_ by
the late J. S. Budgett, who states that the Fish builds enormous nests in
swamps, in about two feet of water; the walls of the nest are made of the
stems of the grasses removed by the Fish from the centre; the floor is the
swamp-bottom, and is made perfectly smooth and bare. The nest appears to be
used for at most four or five days; the newly-hatched larvae are provided
with long external gill-filaments of a blood-red colour.[646]
FAM. 11. PANTODONTIDAE.—The little West African Fish described by Peters as
_Pantodon buchholzi_ is the unique representative of a family closely
related to the Osteoglossidae, but distinguished by the very small, single
praemaxillary and the absence of suboperculum and interoperculum. The
pectoral fins are very large and are remarkable for the fleshy process to
which the inner ray is adnate; the ventrals, formed of 7 rays, some of
which are simple and prolonged into filaments, are placed more forward than
in any other type of this sub-order, the Ctenothrissidae excepted, viz.
immediately behind the pectorals. Teeth in the jaws and on the vomer,
palatines, pterygoids, parasphenoid, {559}glossohyal, and pharyngeal bones.
Mesocoracoid arch slender, strongly curved, and meeting its fellow on the
median line; coracoids forming a ventral keel. Vertebrae few (16 + 14).
[Illustration: FIG. 337.—_Pantodon buchholzi_, natural size.]
Observed by M. de Brazza to be a freshwater Flying-Fish.
[Illustration: FIG. 338.—_Ctenothrissa vexillifer_ (restored by A. S.
Woodward).]
FAM. 12. CTENOTHRISSIDAE.—A curious type characterised by small
praemaxillaries, large maxillaries, with feeble dentition, {560}the
parietals in contact on the median line, vertebral centra without
transverse processes, a moderately large dorsal with simple anterior rays,
and large ventrals advanced far forwards and formed of 8 rays. Its
affinities are still obscure, but the condition of the jaws decides its
allocation to the suborder Malacopterygii, whilst in the position of the
ventrals it is most nearly approached by the Pantodontidae. Small Fishes
known only by two genera, of the Cretaceous period (England and Mount
Lebanon), one with ctenoid scales (_Ctenothrissa_), the other with cycloid
scales (_Aulolepis_).
FAM. 13. PHRACTOLAEMIDAE.—Mouth edentulous, projectile, bordered by the
very slender praemaxillaries and maxillaries. Supraoccipital in contact
with the frontals, widely separating the small parietals; operculum and
suboperculum well developed; praeoperculum small; interoperculum enormous,
covering the gular region and overlapping its fellow; symplectic absent.
Basis cranii single. No pharyngeal teeth. Only 3 slender branchiostegal
rays. Ribs stout, sessile, nearly completely encircling the body; slender
epineurals; no epipleurals; caudal region very short. Supratemporal small,
simple, fixed to the parietal and squamosal; no postclavicle; scapular
foramen in the scapula. Pectoral fin inserted low down, folding like the
ventrals; latter with 6 rays.
[Illustration: FIG. 339.—_Phractolaemus ansorgii_. ⅔ nat. size.]
The remarkable little Fish, _Phractolaemus ansorgii_, discovered by Dr. W.
J. Ansorge in the Niger Delta in 1900, and which has since also been found
in the Congo, stands quite apart among the Malacopterygians, its nearest
allies being apparently the Osteoglossidae. The body is elongate and
subcylindrical, covered with large striated scales; the head is small, the
skull strongly ossified, covered with thin skin; the mouth small,
proboscidiform, {561}capable of being thrust forwards, when at rest folded
over and received into a depression on the upper surface of the head; the
narial orifice is single, and preceded by a barbel; the gill-openings are
narrow, restricted to the sides. The ventral fins are inserted far back,
the dorsal and anal are short. The air-bladder is very large, and the
intestine extremely long and much convoluted. Vertebrae 26 + 8.
FAM. 14. SAURODONTIDAE.—Margin of the upper jaw formed by the
praemaxillaries and the maxillaries, the latter the more developed and
firmly united to the former; these bones, as well as the mandible, with
teeth implanted in deep sockets; palate toothless. Supraoccipital
separating the small parietals; opercular bones well developed; symplectic
present, exposed. Basis cranii double. Ribs sessile, very low down on the
centra; no parapophyses; neural arches not fused with the centra. Pectorals
inserted very low down; postclavicle apparently absent. Caudal fin deeply
forked, without fused hypurals.
This family, comprising several Cretaceous genera, may be regarded as
ancestral to the _Chirocentridae_, with or near which it has been placed by
Cope and various later authors. The normal position of the symplectic,
however, entitles its members to rank as a separate family, and the
autogenous neural arch, as well as the distinctness of the bones supporting
the caudal fin, are also indicative of a greater generalisation. The
restoration of _Ichthyodectes_ as given by Loomis, shows a general form
similar to an ordinary Herring, but it does not appear to be reliable.
The members of the Saurodontidae have been referred to two groups: (_a_)
with praedentary (praesymphysial) bone, _Saurocephalus_, _Saurodon_; (_b_)
without praedentary, _Chirocentrites_, _Portheus_, _Ichthyodectes_,
_Spathodactylus_, _Cladocyclus_. These Fishes are from the Chalk of Europe
and North America, and some among them attain a very large size, perhaps
not less than two metres in length.
FAM. 15. CHIROCENTRIDAE.—Margin of the upper jaw formed by the
praemaxillaries and the maxillaries, the latter the more developed and
firmly united to the former; these bones, as well as the mandible, with
large teeth not implanted in true sockets; minute teeth on the palatines,
pterygoids, and hyoid bones, Supraoccipital in contact with the frontals,
separating the small parietals; opercular bones well developed; symplectic
hidden {562}between the inner surface of the quadrate and a descending
process of the hyomandibular. Basis cranii double. Ribs very slender,
sessile, very low down on the centra; no parapophyses; epipleurals and
epineurals. Pectorals inserted very low down. Post-temporal forked;
postclavicle absent; a thin bony lamina, similar to the postclavicle, above
the pectoral fin, attached to the scapula; scapular foramen in scapula;
coracoids in contact with each other, forming a keel. Ventrals very small,
with 7 rays. Brachiostegal rays 8. Air-bladder large, not communicating
with the ear, incompletely divided into cells. Mucous membrane of the
intestine forming a spiral fold.
The body is very elongate and strongly compressed, covered with thin,
deciduous scales; the vertebrae number 75. The dorsal fin is short and
opposite to the anal, which is long.
[Illustration: FIG. 340.—Side view of skull and pectoral arch of
_Chirocentrus dorab_.]
_Chirocentrus dorab_, the only representative of this family, inhabits the
Indian Ocean and the seas of China and Japan.
FAM. 16. CLUPEIDAE.—Margin of the upper jaw formed by the praemaxillaries
and the maxillaries. Supraoccipital separating the small parietals;
opercular bones well developed. Basis cranii double. Ribs mostly sessile,
inserted behind parapophyses; intermuscular bones (epineurals, epipleurals,
adpleurals) usually numerous. Post-temporal forked, the upper branch
attached to the epiotic, the lower to the opisthotic; post-clavicle applied
to outer side of clavicle. Ventrals with 6 to 11 rays. Air-bladder large,
communicating with the ear.
Four sub-families:—
(i.) THRISSOPATRINAE.—Mouth large; praemaxillaries very small; maxillaries
large, with rather narrow supplemental bone, firmly attached to
praemaxillaries; branchiostegals about 30; abdomen compressed to an edge,
without serration; no lateral line. _Thrissopater_, from the Gault of
Folkestone.
{563}(ii.) ENGRAULINAE.—Mouth moderate or large; praemaxillaries very
small; maxillaries large, with narrow supplemental bones, more or less
firmly attached to praemaxillaries; branchiostegals 6 to 19; abdomen
rounded or more or less compressed, with or without serration; no lateral
line. Recent genera: _Dussumieria_, _Etrumeus_, _Engraulis_,
_Cetengraulis_, _Heterothrissa_, _Coilia_. Fossil: _Spaniodon_, Upper
Cretaceous.
(iii.) CLUPEINAE.—Mouth small or moderate; maxillaries freely movable
behind the praemaxillaries, usually with large supplemental bones;
branchiostegals 5 to 10; abdomen usually serrated; lateral line usually
absent. Recent genera: _Clupea_, _Hyperlophus_ (_Diplomystus_),
_Opisthonema_, _Brevoortia_, _Pellonula_, _Clupeichthys_, _Odaxothrissa_,
_Pellona_, _Chirocentrodon_, _Pristigaster_, _Raconda_, _Chatoessus_.
Fossil: _Pseudoberyx_, _Histiothrissa_, _Scombroclupea_, _Leptichthys_,
Upper Cretaceous.
[Illustration: FIG. 341.—Showing the wide range of variation, within the
family, of the bones (_pm_, praemaxillary, _m_, maxillary) forming the
upper border of the mouth. A, _Dussumieria_; B, _Coilia_; C, _Pellona_; D,
_Chatoessus_; E, _Chanos_. In these semi-diagrammatic figures the orbit is
represented of the same size in all, as affording the best term of
comparison in judging of the relative development of the bones of the upper
jaw.]
(iv.) CHANINAE.—Mouth small, toothless; maxillaries firmly attached to
praemaxillaries; branchiostegals 4, very broad; abdomen rounded or
flattened; lateral line distinct. _Chanos_, recent; _Chanoides_, Upper
Eocene; _Prochanos_, Cretaceous.
{564}Heralded by the genus _Thrissopater_,[647] which may be regarded as a
connecting type between the Elopidae and the Clupeidae, this family is
largely represented in Cretaceous times, more abundantly still in the
Eocene and Miocene, where _Clupea_ and _Engraulis_ occur in numerous
species; _Hyperlophus_, distinguished from _Clupea_ by the presence of a
dorsal serrated ridge similar to the ventral, occurs in the Upper
Cretaceous of Syria, Southern Europe, and South America, in the Eocene of
North America and Europe, and is represented at the present day on the West
Coast of South America and on the coast and in the rivers of New South
Wales. About 200 Clupeids are known to live at the present day, mostly
marine species, but a few are confined to fresh-waters; none may be termed
deep-sea forms; some, like the Allis Shad (_Clupea alosa_) and Twait Shad
(_C. finta_), are anadromous, ascending rivers to spawn. The range of the
family is almost cosmopolitan. Several species are remarkable for the
extreme abundance of individuals, as for example the Herring (_Clupea
harengus_), the Pilchard or Sardine (_C. pilchardus_), and the Anchovy
(_Engraulis encrasicholus_). The Herring inhabits the northern parts of the
Atlantic and the seas north of Asia. As Dr. Günther first showed, the
so-called "Whitebait" consists chiefly of the fry of Herrings, which, like
those of the Sprat (_C. sprattus_), have a predilection for brackish water.
The Anchovy and the Pilchard, on the other hand, seldom if ever enter
estuaries. The eggs of the Herring, contrary to those of most British
marine food-fishes, are heavy and adhesive, sticking firmly to stones or
fixed objects on the sea bottom, whilst those of the Sprat and Pilchard
float on the surface. The larvae are long, slender, and transparent. The
Sardine, which affords so valuable a fishery on the West Coast of France,
is the immature state of the Pilchard, which grows to a length of 10 to 14
inches. Its movements are not yet well understood, and its scarcity during
certain years in the waters where it usually swarms has caused periodical
crises in an important industry. Ripe Pilchards are mostly found at a
considerable distance from the coasts. The Anchovy is especially abundant
in the {565}Mediterranean, but it is also regularly fished in Holland,
especially in the Zuydersee, where it breeds, as well as in the
Mediterranean; it makes only temporary appearances, and has not been
observed to spawn, in the English Channel, although eggs have recently been
obtained off the coast of North Lancashire.[648]
The imperfectly known Cretaceous Crossognathidae (_Crossognathus_ and
_Scyllaemus_), referred by some authors to the Percesoces, should probably
be placed with or near the Clupeidae.
FAM. 17. SALMONIDAE.—Margin of the upper jaw formed by the praemaxillaries
and the maxillaries. Supraoccipital in contact with the frontals, but
frequently overlapped by the parietals, which may meet in a sagittal
suture; opercular bones all well developed. Basis cranii double. Ribs
sessile, parapophyses very short or absent; epineurals, sometimes also
epipleurals, present. Post-temporal forked, the upper branch attached to
the epiotic, the lower to the opisthotic; postclavicle, as usual, applied
to inner side of clavicle. A small adipose dorsal fin. Air-bladder usually
present, large. Oviducts rudimentary or absent, the ova falling into the
cavity of the abdomen before exclusion.
Marine and fresh-water Fishes, mostly from the temperate and Arctic zones
of the northern hemisphere: one genus (_Retropinna_) on the coasts and in
the rivers of New Zealand; a few deep-sea forms (_Argentina_, _Microstoma_,
_Nansenia_, _Bathylagus_) occur in the Arctic Ocean, the North Atlantic
Ocean, the Mediterranean, and the Antarctic Ocean, down to 2000 fathoms.
Apparently of comparatively recent age, no remains older than Miocene
(_Osmerus_, _Thaumaturus_, _Prothymallus_) being certainly referable to
this family. The recent genera may be grouped as follows:—
_A_. Air-bladder present.
_a_. Branchiostegal rays 8 to 20; ventral rays 9 to 13; stomach
siphonal; pyloric appendages more or less numerous (17 to 200). Breed
in fresh water. _Salmo_, _Brachymystax_, _Stenodus_, _Coregonus_,
_Phylogephyra_, _Thymallus_.
_b_. Branchiostegal rays 6; ventral rays 11 to 14; stomach caecal;
pyloric appendages in moderate numbers (12 to 20). _Argentina_.
{566}_c_. Branchiostegal rays 6 to 10; ventral rays 6 to 8; stomach
caecal; pyloric appendages few (2 to 11) or rather numerous. _Osmerus,
Thaleichthys, Mallotus, Plecoglossus, Hypomesus_.
_d_. Branchiostegal rays 3 or 4; ventral rays 8 to 10; stomach caecal;
pyloric appendages absent. _Microstoma, Nansenia, Bathylagus_.
B. Air-bladder absent; branchiostegal rays 3 to 6; ventral rays 6 or 7;
stomach siphonal; pyloric appendages absent. _Retropinna, Salanx_.
Only about 80 species can, at present, be regarded as valid.
[Illustration: FIG. 342.—Distribution of Salmonidae (deep-sea forms not
included).]
The beauty, gameness, and great economical value of the Salmonids have
caused more attention to be bestowed on them than probably upon any other
group of fishes. As Professor Smitt tells us, a Swedish proverb says "A
dear child has many names," and this applies well to our Salmon and Trout,
the species of which have been unduly multiplied by some writers. The genus
_Salmo_, characterised by a large mouth and powerful dentition, is divided
into three sections: _Oncorhynchus_, Quinnat Salmon, of the North Pacific,
ascending rivers in North America and Asia, with 12 to 17 developed rays in
the anal; _Salmo_, Salmon and Trout, with 8 to 12 rays in the anal, and
teeth not only on the head of the vomer but also along its shaft, at least
in the young, {567}represented in the seas and freshwaters of Europe, Asia,
and North America, extending southwards to North-West Africa, Asia Minor,
Northern Persia, the Hindu Kush, the head of the Gulf of California, and
the Rio Grande; _Salvelinus_, Charr, with 8 to 10 rays in the anal, and
teeth on the raised head of the vomer only, of the lakes of Northern and
Central Europe and the rivers of the northern parts of Asia and North
America as far north as 82° 34´, sometimes descending to the sea.
[Illustration: FIG. 343.—Trout (_Salmo trutta_). × ⅓. (After
Valenciennes.)]
The changes in form and colour which these fishes undergo when passing from
fresh water into the sea or when artificially transported from one place to
another are very great, and this plasticity, together with the connecting
links which render the naming of not a few specimens impossible, have
caused most recent students of the genus _Salmo_, in Europe at least, to
reduce many of the so-called species to the rank of local varieties, and
even our common Brown Trout or Brook Trout (_S. fario_) is now generally
regarded as not specifically separable from the anadromous Sea Trout (_S.
trutta_). The anadromous true Salmon (_S. salar_) may be distinguished by
its somewhat larger scales, there being only 11 or 12 in a transverse
series running from the posterior border of the adipose fin forwards to the
lateral line, Trout having 13 to 16. The Charr of the lakes of Wales, the
North of England, Scotland, and Ireland are also regarded as mere varieties
of the common Northern migratory Charr (_S. alpinus_), of which the "Omble
Chevalier" of the Swiss lakes and the "Saeblings" of the Alpine lakes of
Germany and Austria are likewise varieties. An allied species (_S.
fontinalis_) has been introduced into England from North America, as well
as a true Trout (_S. irideus_). The large size of the eggs, their lack of
{568}adhesiveness, and the fact that the ova fall into the abdominal
cavity, out of which they may easily be squeezed, renders artificial
impregnation particularly easy, and the species of _Salmo_ have always
occupied the first place in the annals of fish-culture. Fertilised eggs are
transported in ice, the development being simply suspended for several
weeks, and several forms of British and American Salmonidae have thus been
introduced into New Zealand and Tasmania, where some have thoroughly
established themselves.
The White-Fish, _Coregonus_, are more numerous in species than _Salmo_, and
as a rule more readily defined. They are easily recognised by their large
silvery scales and their smaller mouth without or with minute teeth. Some,
like the Houting (_C. oxyrhynchus_) of Northern Europe, occur in the sea,
entering rivers to spawn, whilst others, like the Sik, Weiss, Felchen, or
Lavaret (_C. lavaretus_), are confined to lakes. British species are the
Gwyniad (_C. clupeoides_), of Loch Lomond, Haweswater, Ullswater, and Bala,
the Vendace (_C. vandesius_), of Loch Maben, and the Pollan (_C. pollan_)
of Lough Neagh in Ireland.
[Illustration: FIG. 344.—Capelin (_Mallotus villosus_.) ½ nat. size. (After
Valenciennes.)]
The Grayling (_Thymallus vulgaris_ or _vexillifer_), with its high dorsal
fin formed of about 20 rays, one of the handsomest British fishes, inhabits
the rivers and lakes of Northern and Central Europe, and is represented by
a few allied species in Asia and North America. It derives its name from
having the odour of thyme.
The Smelt (_Osmerus eperlanus_) breeds in salt water, and although it often
enters rivers, it does not ascend beyond tidal influence. The Capelin
(_Mallotus villosus_), of the coasts of Arctic America and North-eastern
Asia, deposits its eggs in the sand along the shores in incredible numbers,
the beach becoming a {569}quivering mass of eggs and sand. _Plecoglossus_,
from Japan and Formosa, is highly remarkable for its lamellar, comb-like,
lateral teeth. The Siel-Smelts (_Argentina_) are deep-sea Salmonids of
which examples have occasionally been taken off the coasts of Scotland and
Ireland; large numbers have been brought from Norway to English markets.
_Bathylagus_ is still better adapted for life at great depths (down to 1700
fathoms), the eyes being of enormous size. As Dr. Günther has observed,
"these fishes must be entirely dependent for vision on the phosphorescent
light which is produced by other abyssal creatures. Not being fish of prey
themselves, or only to a slight degree, they would be attracted by the
light issuing from the Pediculates and Stomiatids of the deep, and thus
form an easy prey to these fishes."
Secondary sexual characters are very strongly developed in many Salmonids.
In adult males of Salmon, Trout, and Quinnat the snout becomes greatly
distorted, both jaws being hooked and the base of the teeth more or less
enlarged; in the latter species a fleshy hump is developed before the
dorsal fin, and the scales of the back become embedded in the flesh.
Pearl-like excrescences appear on the scales of many of the White-Fish
during the breeding season, being more prominent in males than in females,
and _Mallotus villosus_ is so called from the villous bands formed by the
scales of mature males, the scales above the lateral line and along each
side of the belly becoming elongate-lanceolate, densely imbricated and
produced into free, projecting points.[649]
The Pachyrhizodontidae, with the Cretaceous genus _Pachyrhizodus_, are
placed by some authors with the Salmonidae, but the remains at present
known are too fragmentary to afford a correct idea of their exact
systematic position. There seems to be less justification for placing them
among the Elopidae.
FAM. 18. ALEPOCEPHALIDAE.—Deep-sea Fishes similar in general structure to
the Clupeidae and Salmonidae, but destitute of a postclavicle and of an
adipose dorsal fin,[650] the rayed fin being situated far back on the body,
in the caudal region, and opposed {570}or slightly anterior to the anal.
The skeleton of _Alepocephalus_[651] is remarkable for its feeble
ossification. Epipleurals and epineurals are present, and the bilateral
division of the neural arch remains perfectly distinct throughout the
praecaudal region, both halves being very loosely apposed. The air-bladder
is absent. Ventrals are absent in _Platytroctes_, and the snout is much
produced in _Aulostomatomorpha_.
Eleven genera are distinguished:—A, with scales: _Alepocephalus_,
_Conocara_, _Bathytroctes_, _Leptochilichthys_, _Narcetes_, _Platytroctes_,
_Aulostomatomorpha_. B, without scales:—_Xenodermichthys_, _Aleposomus_,
_Leptoderma_, _Anomalopterus_.
Represented by about 35 species in nearly all the seas; as usual with
deep-sea forms, individuals of the same species have been obtained from
stations very remote from one another.
[Illustration: FIG. 345.—_Malacosteus indicus_. (After Günther.)]
FAM. 19. STOMIATIDAE.—I would unite under this name the Stomiatidae and
Sternoptychidae of Günther, an assemblage of aberrant deep-sea Fishes which
agree in having the maxillary bone more developed than the praemaxillary,
and beset with teeth, a character which differentiates them at once from
all other deep-sea forms of this sub-order, as well as from the Scopelidae
among the Haplomi. The ventral fins are usually inserted very far back, and
the number of their rays varies from 5 to 8. Contrary to what occurs in
other groups of fishes, the pectoral fins have a tendency to reduction, and
actually disappear in some genera, whilst the ventrals remain well
developed; whenever the pectoral fins are fully developed, as in
_Maurolicus_, _Chauliodus_, _Astronesthes_, and _Photichthys_, the
mesocoracoid arch is present.[652] The form of the body varies exceedingly,
even within the smaller groups into which this family has been divided; it
may be excessively short and compressed, or excessively elongate, {571}but
the mouth and eyes are always large, these fish being essentially
predatory; the dentition is often very powerful, and may extend to the
palate or be confined to the jaws. The body is naked or scaly; luminous
spots (photophores) are more or less developed.[653] The development and
position of the vertical fin is highly variable within this group, and the
several families which have been founded upon this character have no more
taxonomic importance than in the better-understood groups _Characinidae_
and _Siluridae_. All authors, besides, have been compelled to admit that
the presence or absence of an adipose dorsal fin has no high significance
in this case, a view which is further strengthened by Dr. Gilchrist's
discovery, off the Cape of Good Hope, of a deep-sea Fish agreeing in every
respect with _Astronesthes_, but for the presence of a small adipose fin,
absolutely similar to the dorsal, but situated on the ventral side,
immediately in front of the anus. Two species with similar ventral adipose
fins have just been discovered by Dr. Brauer and referred to
_Astronesthes_. I am therefore unable to adopt the elaborate arrangement in
favour with the modern American school.
[Illustration: FIG. 346.—_Sternoptyx diaphana_. (After Günther.)]
The genera may be arranged in five sub-families:—
I. Anal not exactly opposed to the rayed dorsal, or much longer than the
latter; no hyoid barbel.
_A_. Rayed dorsal far forward, between pectorals and ventrals;
pectorals well developed (CHAULIODONTINAE). _Chauliodus_.
_B_. Rayed dorsal above or behind the ventrals; pectorals well
developed.
1. Body more or less elongate; ventrals well developed
(GONOSTOMATINAE).
_a_. A hyoid barbel. _Astronesthes_.
_b_. No barbel. _Bathylychnus_, _Gonostoma_, _Cyclothone_,
_Triplophos_, _Photichthys_, _Bathylaco_, _Diplophos_,
_Maurolicus_, _Ichthyococcus_.
2. Body short and deep; ventrals rudimentary or absent
(STENOPTYCHINAE). _Argyropelecus_, _Sternoptyx_, _Polyipnus_.
II. Dorsal and anal opposed to each other and very far back on the caudal
region; pectorals often reduced or absent; hyoid barbel often present.
{572}(STOMIATINAE). _Stomias, Macrostomias, Echiostoma, Opostomias,
Pachystomias, Photonectes, Malacosteus, Thaumatostomias, Photostomias_.
This family, comprising about 55 species, has a world-wide distribution,
but most of the known forms have been obtained from the Atlantic; some of
the species occur both in the Atlantic and the Indo-Pacific. _Chauliodus_,
_Astronesthes_, and _Stomias_ are among the fishes with the most formidable
dentition.
FAM. 20. GONORHYNCHIDAE.—Margin of the upper jaw formed by the
praemaxillaries and the maxillaries, the latter articulated above the
former to the ethmoid. Supraoccipital in contact with the frontals, widely
separating the small parietals; opercular bones well developed; symplectic
present. Basis cranii simple. Mouth small and toothless, inferior,
surrounded by thick, fringed lips. Four branchiostegal rays. Head and body
entirely covered with small spiny scales. Praecaudal vertebrae with strong
parapophyses, to the extremity of which slender ribs and epipleurals are
attached. No postclavicle. Pectoral fins inserted low down, folding like
the ventrals; latter with 10 rays.
[Illustration: FIG. 347.—_Gonorhynchus greyi_. ⅓ nat. size. (After
Valenciennes.)]
The single existing species, _Gonorhynchus greyi_, is characterised by an
elongate, cylindrical body, a pointed projecting snout bearing a single
barbel, short dorsal and anal fins, the former opposed to the ventrals, and
the gill-membranes broadly attached to the isthmus. Teeth are present on
the pterygoid and hyoid bones. No suborbital arch. Vertebrae, 45 + 20.
Air-bladder absent. Its distribution is a very wide one, the species being
on record from the coasts of the Cape of Good Hope, Australia, New Zealand,
and Japan.
The genus _Notogoneus_, from the freshwater Eocene beds of France and North
America, has been referred to this family by Cope, and has been shown by A.
S. Woodward to be closely related to _Gonorhynchus_, differing only in the
absence of teeth on the palate and tongue, and in the more forward position
of the dorsal fin. The genus _Charitosomus_, with several species {573}from
the Upper Cretaceous of Westphalia and Mount Lebanon, has also been
included in this family, but the precise shape and character of the scales
have not yet been ascertained.
FAM. 21. CROMERIIDAE.—Margin of the upper jaw formed by the praemaxillaries
and the maxillaries. Supraoccipital large and widely separating the very
small parietals; opercular bones well developed; symplectic absent. Basis
cranii simple. Mouth small and toothless, inferior; gill-opening narrow.
Three branchiostegal rays. Body naked. Praecaudal vertebrae with
parapophyses; ribs and epipleurals slender. No postclavicle. Pectoral fin
inserted low down, folding like the ventrals.
A single genus, _Cromeria_, recently discovered in the White Nile. In its
elongate, naked body and the posterior position of the dorsal fin, it
resembles the Galaxiidae, to which it was at first referred. But this
allocation has proved to be incorrect, now that the osteological structure
of the minute Fish (only about 30 mm. long) has been worked out by
Swinnerton.[654] The vertebrae number 42 to 45 (28-30 + 14-15). A long,
slender air-bladder is present.
SUB-ORDER 2. OSTARIOPHYSI.
Air-bladder, if well developed, communicating with the digestive tract by a
duct. Pectoral arch suspended from the skull; mesocoracoid arch present.
Fins without spines, or dorsal and pectoral with a single spine formed by
the co-ossification of the segments of an articulated ray. The anterior
four vertebrae strongly modified, often co-ossified and bearing a chain of
small bones (so-called Weberian ossicles) connecting the air-bladder with
the ear.
This is one of the most natural groups of the Class Pisces, although its
members are so diversified in outward appearance as to have been widely
separated in the systems of older authors. It is to Sagemehl[655] that is
due the credit of having first grouped, under the above name, the
Characines, the Carps, the Cat-Fishes, and the Gymnotids, the relations of
which had been realised, to a certain extent, by Cope. But it was not until
the homology throughout the group of the ossicula auditus, first described
by E. H. Weber in 1820, had been demonstrated by Sagemehl that the
justification for the course here followed appeared in its full
{574}strength, as such an agreement in the structure of so complicated and
specialised an apparatus can only be the result of a community of descent
of the families which are possessed of it. It is invariably the anterior
four vertebrae that take part in the support of the Weberian apparatus. The
first vertebra is much reduced; its upper arch is absent and replaced by
the ossicles termed _claustrum_ and _scaphium_[656] (the former being
perhaps nothing but the modified neural arch), which fill in the space
between the exoccipital and the neural arch of the second vertebra; the
principal piece of the apparatus, the _tripus_, variable in form, is
related to the third vertebra, of which it is regarded as a modified rib; a
fibrous ligament extends from the anterior extremity of the _tripus_ to the
_scaphium_, and in this ligament is inserted the fourth piece, the
_intercalarium_. The various forms of this sub-order also show a complete
agreement in the spinal nerves which pass through these ossicles. The
parietal bones either separate the frontals from the supraoccipital or are
fused with the latter.
This sub-order is divided into six families. The Characinids are the most
generalised, and the others are probably derived from them in the manner
expressed by the following diagram:—
_Loricariidae_ _Aspredinidae_
| |
+––––––––––––+––––––––––+
|
_Cyprinidae_ _Siluridae_ _Gymnotidae_
| | |
+–––––––––––+–––––––––––+ |
| |
+–––––––––––––––––––+–––––––––––––––––+
|
_Characinidae_.
SYNOPSIS OF THE FAMILIES
I. Parietal bones distinct from the supraoccipital; symplectic present;
ribs mostly sessile, all or the greater number of the praecaudal
vertebrae without parapophyses.
Mouth not protractile, usually toothed; pharyngeal bones normal; body
scaly; an adipose dorsal fin often present 1. _Characinidae_.
Mouth not protractile, usually toothed; pharyngeal bones normal; body
Eel-shaped, naked or scaly; vent under the head or on the throat
2. _Gymnotidae_.
Mouth usually more or less protractile, toothless; lower {575}
pharyngeal bones large, falciform; body naked or scaly; no
adipose dorsal fin 3. _Cyprinidae_.
II. Parietal bones usually fused with the supraoccipital; symplectic
absent; body naked or with bony scutes; mouth usually toothed, with
barbels; adipose fin often present.
Ribs attached to strong parapophyses; operculum well developed
4. _Siluridae_.
Ribs sessile; parapophyses absent; operculum more or less developed;
mouth inferior 5. _Loricariidae_.
Ribs sessile; strong parapophyses to the vertebrae; operculum absent
6. _Aspredinidae_.
FAM. 1. CHARACINIDAE.—Mouth non-protractile, usually bordered by the
praemaxillaries and the maxillaries, rarely by the praemaxillaries only;
jaws usually toothed. Parietal bones united in a sagittal suture or
separated by a fontanelle; opercular bones well developed; symplectic
present. Pharyngeal bones normal, with small teeth. Ribs mostly sessile; no
parapophyses in the thoracic region; epipleurals and epineurals, mostly
free floating. Pectoral fins inserted very low down, folding like the
ventrals. Body covered with scales. An adipose dorsal fin often present.
This is a very generalised type, although perhaps not directly derived from
the bony Ganoids, as believed by Sagemehl. The species number about 500,
and are confined to the freshwaters of Africa and Central and South
America. The classification of the family is still in an unsatisfactory
state, but the division into the following groups (hardly deserving the
rank of sub-families), although quite provisional, appears preferable to
the highly artificial arrangement hitherto adopted:—
I. No adipose fin.
A. ERYTHRININAE.—Carnivorous; teeth strong; maxillary large;
gill-openings wide; scales cycloid. American: _Macrodon_, _Erythrinus_,
_Lebiasina_, _Pyrrhulina_, _Corynopoma_.
II. Adipose fin usually present.
B. HYDROCYONINAE.—Entirely or partially carnivorous; teeth strong;
maxillary well developed; scales cycloid; lateral line usually nearer
ventral than dorsal outline (sometimes only on the tail). African:
_Sarcodaces_, _Hydrocyon_, _Bryconaethiops_, _Alestes_, _Micralestes_,
_Petersius_. American: _Acestrorhynchus_, _Boulengerella_,
_Acestrorhamphus_, _Crenuchus_, _Chalceus_, _Brycon_, _Bryconops_,
_Bryconodon_, _Creagrutus_, _Chalcinus_, _Brachychalcinus_,
_Pseudocorynopoma_, _Stichonodon_, _Gastropelecus_, _Tetragonopterus_,
_Scissor_, _Chirodon_, _Piabucina_, _Iguanodectes_, _Aphiocharax_,
_Salminus_, _Oligosarcus_, _Agoniates_, _Paragoniates_,
_Leptagoniates_, _Anacyrtus_.
{576}C. SERRASALMONINAE.—Carnivorous; teeth strong; belly serrated;
scales cycloid. American: _Serrasalmo_, _Myletes_, _Myleus_,
_Metynnis_, _Catoprion_.
D. ICHTHYOBORINAE.—Carnivorous; teeth strong; maxillary very small;
upper jaw movable; scales ciliated. African: _Eugnathichthys_,
_Paraphago_, _Mesoborus_, _Phago_, _Ichthyoborus_, _Neoborus_.
E. XIPHOSTOMINAE.—Carnivorous; teeth very small; maxillary rather
small; scales ciliated. American: _Xiphostoma_.
F. ANOSTOMINAE.—Herbivorous, entirely or partially; teeth well
developed in both jaws; maxillary very small; gill-openings narrow;
scales cycloid. American: _Anostomus_, _Leporinus_, _Characidium_,
_Chorimycterus_, _Nanostomus_, _Nanognathus_.
G. HEMIODONTINAE.—Partially herbivorous; dentition imperfect; maxillary
well developed; scales cycloid. American: _Hemiodus_, _Caenotropis_,
_Saccodon_, _Parodon_.
H. DISTICHODONTINAE.—Entirely or partially herbivorous; teeth small but
well developed; maxillary well developed; scales ciliated. African:
_Nannaethiops_, _Neolebias_, _Distichodus_, _Nannocharax_,
_Xenocharax_.
I. CITHARININAE.—Herbivorous; teeth minute or absent; maxillary small;
scales cycloid or ciliated. African: _Citharinus_, _Citharidium_.
American: _Prochilodus_, _Curimatus_.
[Illustration: FIG. 348.—Distribution of the Characinidae.]
The genera in the above sub-families are mostly founded on the dentition
and the extent of the praemaxillary and maxillary bones, which are
astonishingly varied, as may be seen from the annexed figures showing the
open mouths of a few of the most remarkable types. As I have already
pointed out, the character often given as diagnostic of this family, viz.
the maxillary forming part of the oral border, is not absolutely constant;
this bone is often much reduced, and it is entirely excluded from the mouth
in _Ichthyoborus_ and _Neoborus_. The branchiostegal rays {577}number 3 to
5 only. The fins never bear pungent spines, and the ventrals have 6 to 13
rays. Barbels are absent. In most of the herbivorous forms the brain-case
is produced forward to the nasal capsule, whilst in most of the carnivorous
forms they are separated by an interorbital septum; but there are
exceptions to this correlation, and as otherwise closely related genera may
differ in this respect, I have not been able to make use of the character
in defining sub-families.
[Illustration: FIG. 349.—Open mouths of Characinidae. (After Müller and
Troschel.) A, _Macrodon trahira_; B, _Piabucina argentina_; C, _Brycon
falcatus_; D, _Chalceus angulatus_; E, _Serrasalmo rhombeus_; F,
_Distichodus niloticus_.]
{578}The air-bladder is divided into an anterior and a posterior part by a
constriction; the posterior part is the longer, and its anterior portion is
cellular in _Erythrinus_ and _Lebiasina_. Pyloric appendages to the
stomach, which are constantly absent in the Cyprinids, are more or less
numerous. An accessory respiratory organ in a diverticulum above the fourth
branchial arch has been observed in _Xenocharax_ and _Citharinus_.
[Illustration: FIG. 350.—_Hydrocyon goliath_, from the Congo. ⅒ nat. size.]
The appearance and habits of the genera which compose this family vary
greatly. Some resemble the Cyprinids and are mainly vegetarians, whilst
others recall Salmonids and Pike. Among the most formidable are
_Hydrocyon_, the Dogs of the Water, or Kelb-el-Bahr of the Arabs, with
their powerful jaws with shark-like teeth, visible when the mouth is
closed, and which grow to the size of the Salmon. The five known species
inhabit the Nile and the rivers and lakes of tropical Africa. No less
ferocious are the "Piranha" or "Cariba" (_Serrasalmo_) of South America,
whose bite has been compared to the cut of a razor. They abound in some
rivers and are much dreaded by people having to enter the water, as they
fiercely bite off big pieces of flesh as with a pair of scissors, and the
smell of blood is said to attract them by thousands; they show a great
tenacity of life and can remain for hours out of the water. _Serrasalmo
niger_ has been observed by Schomburgk to produce a grunting noise in the
water. _Salminus orbignianus_, of the Plate River, "Dorado" of the
Spaniards, which reaches a length of 3 feet, has the predacious habits of
the Pike, and follows other fishes moving in shoals; its flesh is much
valued, although very full of bones, like that of all Characinids.
{579}As an example of phytophagous types may be mentioned the Moon-Fish of
the Nile (_Citharinus geoffroyi_), with its feeble dentition, deep
compressed body, and falciform dorsal fin; it is often represented on the
monuments of the ancient Egyptians.[657]
FAM. 2. GYMNOTIDAE.—Mouth non-protractile, bordered by the praemaxillaries
and the maxillaries, the latter sometimes much reduced; jaws usually
toothed. Parietal bones united in a sagittal suture, or separated by a
fontanelle; opercular bones well developed; symplectic present. Pharyngeal
bones normal, with small teeth. Anterior ribs sessile, the posterior
inserted on transverse processes; epipleurals and epineurals. Body much
elongate, Eel-like, naked or scaly; dorsal fin absent or reduced to an
adipose strip; anal very long; caudal rudimentary or absent;[658] ventrals
absent. Vent under the head or at a very short distance behind the throat.
Gill-openings narrow.
In spite of their external appearance, these fishes have nothing to do with
the Eels; they are strongly modified, degraded Characinids, as first
pointed out by Reinhardt. The few genera and species (about 30) are
confined to the fresh waters of Central and South America. No fossils are
known. Eight genera may be distinguished:—
A. A cranial fontanelle; maxillary bone larger than the praemaxillary;
anterior nostril on the upper surface of the head; vent below the head;
body scaly: _Sternopygus_, _Eigenmannia_, _Sternarchus_,
_Rhamphosternarchus_, _Rhamphichthys_, _Steatogenys_.
B. No cranial fontanelle; maxillary bone very small; anterior nostril on
the upper lip; vent on the throat.
_a_. Body scaly: _Carapus_.
_b_. Body naked; an electric organ: _Gymnotus_.
The mouth is small or very small, and the modifications of the snout in the
genera _Sternarchus_ and _Rhamphichthys_ recall those noticed among the
Mormyridae. The air-bladder is divided into an anterior and a posterior
part, united by a slender duct.[659] The vertebrae vary in number from 70
(_Sternopygus_) to 240 (_Gymnotus_). _Gymnotus_ is unique in this sub-order
in having as many as 8 pterygials (actinosts) to the pectoral fin, as in
_Anguilla_.
{580}[Illustration: FIG. 351.—Outlines of heads, showing shape of snout and
position of vent (_v_). A, _Sternarchus albifrons_; B, _Sternarchus
macrostoma_; C, _Rhamphosternarchus curvirostris_; D, _Rhamphosternarchus
tamandua_.]
The best known member of this family is the so-called Electric Eel
(_Gymnotus electricus_), of the Orinoco, Amazons, and intermediate
river-systems. It grows to a length of 8 feet and the thickness of a man's
thigh, and is much feared for the electric shocks it is able to discharge.
The "Tremblador," as it is called by the Spanish-speaking inhabitants of
the Orinoco district, is found only in marshes and in comparatively shallow
parts of rivers, to the great annoyance of travellers who have to ford at
such points, beasts of burden being frequently knocked down by the electric
shock. Specimens have often been exhibited alive in this country; two
brought to London in the year 1842, neither of them weighing more than one
pound, had by 1848 reached the weights of 40 and 50 pounds respectively.
About four-fifths of the length of the fish is occupied by the tail, which
contains the electric organ; this is formed by modified muscular tissue,
and consists of two huge masses, longitudinal bands or columns, of cells
filled with a jelly-like substance, occupying the whole of the caudal
region below the vertebral column and separated by a narrow median septum;
a smaller body, of similar structure, extends along each side at the base
of the anal fin. The whole apparatus is supplied with a great number of
nerves branching from the spinal nerves. The electrical apparatus is
exercised by the will of the fish, even to {581}a distance, but this
faculty is exhausted by continuous employment, and is recovered during
repose. Although apparently not exempt from exaggeration and fable,
Humboldt's account in _Observations de Zoologie_, p. 497, is recommended
for further information on the habits and modes of capture of
_Gymnotus_.[660]
FAM. 3. CYPRINIDAE.—Mouth usually more or less protractile, toothless,
bordered by the praemaxillaries and the maxillaries, or, more frequently by
the praemaxillaries only. Parietal bones united in a sagittal suture, or
separated by a fontanelle; opercular bones well developed; symplectic
present. Lower pharyngeal bones falciform, subparallel to the branchial
arches, provided with teeth arranged in one, two, or three series, and
often remarkably specialised. Ribs mostly sessile; no parapophyses in the
thoracic region; epipleurals and epineurals, mostly free, floating.
Pectoral fins inserted very low down, folding like the ventrals. Body naked
or scaly. No adipose dorsal fin.
The brain-case is produced forward to the nasal capsule. The branchiostegal
rays are reduced to 3; the branchiostegal membrane is usually more or less
extensively grown to the isthmus. The suborbital branch of the sensory
canals is usually produced on the operculum, as in the Characinidae. The
ventral rays number 7 to 12, rarely 5 or 6. Pyloric appendages to the
stomach are absent.
Freshwater fishes feeding on vegetable substances or small animals, and
dispersed over the whole world with the exception of South America,
Madagascar, Papuasia, and Australasia. The species are exceedingly
numerous, about 1300 being known, referable to four sub-families, as
proposed by Sagemehl.
(i.) CATOSTOMINAE.—Margin of upper jaw formed in the middle by the small
praemaxillaries and on the sides by the maxillaries, which are hidden in
thick fleshy lips; no barbels; pharyngeal teeth in a single row, very
numerous, comb-like; air-bladder large, divided into two or three parts by
transverse constrictions, not surrounded by a bony capsule. Mostly from
North America; two species from China and one from Eastern Siberia. Fossil
in the Lower Tertiary of North America.
Principal genera:—_Sclerognathus_, _Carpiodes_, _Catostomus_, _Moxostoma_.
{582}(ii.) CYPRININAE.—Maxillaries not bordering the mouth; barbels absent,
or one or two pairs; pharyngeal teeth in one to three rows, in small
number, often very large, and working against a sclerous plate attached to
a ventral process of the basi-occipital, which extends under the anterior
vertebrae. Air-bladder usually large and divided into an anterior and a
posterior part, rarely tripartite, not surrounded by a bony capsule. The
great bulk of the family, represented in every part of its range. Remains
of several of the existing genera have been found in Oligocene and later
beds of Europe, Sumatra, and North America.
Principal genera:—_Cyprinus_, _Catla_, _Catlocarpio_, _Osteochilus_,
_Labeo_, _Discognathus_, _Psilorhynchus_, _Capoëta_, _Barbus_, _Gobio_,
_Pseudogobio_, _Saurogobio_, _Rhinogobio_, _Oreinus_, _Schizothorax_,
_Ptychobarbus_, _Gymnocypris_, _Diptychus_, _Aulopyge_, _Ceratichthys_,
_Pimephales_, _Campostoma_, _Cochlognathus_, _Exoglossum_, _Meda_,
_Lepidomeda_, _Rhinichthys_, _Rohteichthys_, _Leptobarbus_, _Rasbora_,
_Luciosoma_, _Nuria_, _Amblypharyngodon_, _Cyprinion_, _Semiplotus_,
_Xenocypris_, _Leuciscus_, _Tinca_, _Leucosomus_, _Chondrostoma_,
_Achilognathus_, _Rhodeus_, _Danio_, _Pteropsarion_, _Hypophthalmichthys_,
_Abramis_, _Nematabramis_, _Aspius_, _Leucaspius_, _Alburnus_, _Barilius_,
_Bola_, _Neobola_, _Chelaethiops_, _Chela_, _Culter_, _Pelecus_,
_Parapelecus_, _Cachius_, _Opsariichthys_, _Scombrocypris_,
_Squaliobarbus_, _Luciobrama_.
(iii.) COBITIDINAE.—Maxillaries not bordering the mouth; barbels three to
six pairs; pharyngeal teeth in one row, in moderate number. Anterior part
of the air-bladder divided into a right and left chamber separated by a
constriction, and enclosed in a bony capsule, the posterior part free, or
absent. Loaches, characterised externally by a low, elongate body, without
or with minute scales. Europe, Asia, Abyssinia. Miocene of Oeningen.
Principal genera:—_Botia_, _Lefua_, _Diplophysa_, _Nemachilus_,
_Misgurnus_, _Cobitis_, _Lepidocephalichthys_, _Acanthophthalmus_,
_Eucirrhichthys_, _Apua_.
(iv.) HOMALOPTERINAE.—Maxillaries not bordering the mouth, which is
inferior; barbels three or four pairs; pharyngeal teeth in one row, in
moderate number. Air-bladder rudimentary, divided into two lateral halves,
encased in a bony capsule. Mountain forms with depressed head and
horizontally expanded paired fins. China, India, Further India, Malay
Peninsula and Archipelago.
Genera:—_Homaloptera_, _Helgia_, _Glaniopsis_, _Gastromyzon_.
The recently described _Gyrinochilus_, from Borneo, resembling
{583}_Homaloptera_ in habit, with two gill-clefts on each side, an upper
and a lower, a tadpole-like mouth without barbels, and a small, free
air-bladder, should probably be regarded as the type of a fifth sub-family.
Many of the genera of the Cyprininae are partly founded on the shape and
the disposition of the pharyngeal teeth, which, adapted to various
requirements, may be conical, hooked, spoon-shaped, molariform, etc., etc.
The importance attached to the disposition of these teeth in one, two, or
three series for the definition of genera, has been rather
exaggerated.[661]
[Illustration: FIG. 352.—Lower pharyngeals of _Barbus tropidolepis_.]
[Illustration: FIG. 353.—_Labeo falcifer_, from the Congo, showing nuptial
tubercles on the snout. ¼ nat. size.]
The Cyprinids constitute the majority of the freshwater fishes in Europe,
Asia, and North America; they are comparatively few (about 100 species) in
Africa, where they coexist with the Characinids. Some, like the Carp
(_Cyprinus carpio_) and the Tench (_Tinca vulgaris_), are sluggish, except
during the breeding season, when they show great excitement and indulge in
leaps out of the water; others, like the Bleak (_Alburnus lucidus_) are
constantly on the move in large shoals near the surface; whilst others
again, like the M‘Biriki of Lake Tanganyika (_Barbus tropidolepis_), behave
after the manner of Salmon and Trout, {584}travelling long distances,
against rapids and over waterfalls, to reach their breeding places at the
heads of rivers. During the breeding season, the males of many species
assume a more brilliant livery, or develop pearl-like or spiny excrescences
on various parts of the head, or also on the body and fins.[662] Cyprinids
are oviparous, with the exception of a small Barbel from Natal, discovered
and described by Prof. Max Weber as _Barbus viviparus_.
A most striking instance of symbiosis is offered by a little Carp-like fish
of Central Europe, the "Bitterling" (_Rhodeus amarus_). The genital papilla
of the female acquires a great development during the breeding season,
becoming produced into a tube nearly as long as the fish itself; by means
of this ovipositor the comparatively few and remarkably large eggs,
measuring 3 millimetres in diameter—the fish being only 60 to 80
millimetres long—are introduced through the gaping valves, between the
branchial laminae of pond mussels (_Unio_ and _Anodonta_) where, after
being inseminated, they undergo their development, the fry leaving their
host about a month later, having attained a length of 10 or 11
millimetres.[663] The mollusc reciprocates by throwing off its embryos on
the parent fish, in the skin of which they remain encysted for some time,
the period of reproduction of the fish and mussel coinciding.
Some members of this family grow to a very large size,—4 to 6 feet; such is
the case with the Carp, a native of Asia, introduced into England towards
the beginning of the seventeenth century; the Catla (_Catla buchanani_) of
India, Burma, and Siam; the Mahaseer (_Barbus mosal_) of the mountain
streams of Asia, the scales of which may be as large as the palm of a hand;
and _Hypophthalmichthys molitrix_ of China and Manchuria, remarkable for
the low position of the eyes, the fusion of the gill-rakers into thin
plates of spongious appearance, which must act as a most efficient sifting
apparatus, and the presence of an involuted problematic superbranchial
organ to each branchial arch.[664]
Among well-known aberrations produced by artificial selection may be
mentioned the "Leather Carp," a race in which the scales are either lost or
much reduced in number, and enlarged {585}along the lateral line and the
back, and the Gold-Fish, a variety of _Cyprinus carassius_, remarkable for
its golden or bright red colour, or its perfect albinism, as well as its
monstrous form the Telescope Fish, with enormously projecting eyes, and
enlarged, horizontally spread caudal fin.[665] This family has also yielded
numerous more or less well-established examples of hybridism, congeneric
and digeneric, originally described as distinct species, the produce of
which is believed to be in some cases fertile for at least one generation.
The crystalline silvery colouring matter of various Cyprinids is said to
have been employed from time immemorial for ornamental purposes by the
Chinese. The well-known and important industry of "Essence Orientale" and
artificial pearls, carried on in France and Germany with the scales of the
Bleak, was not introduced before the middle of the seventeenth century.
[Illustration: FIG. 354.—Pond Loach (_Misgurnus fossilis_), with lower view
of mouth. ⅓ natural size.]
The Loaches, Cobitidinae, which form a very natural sub-family, are small
fishes, few species growing to a foot in length, mostly living in small
streams and ponds. Many delight in the mud at the bottom, in which they
move like Eels. In some cases, the branchial respiration appears to be
insufficient, and the intestinal tract acts as an accessory breathing
organ. The air-bladder, which is partially encased in a bony capsule, may
be so reduced as to lose its hydrostatic functions and becomes transformed
into a sensory organ, its outer exposed surface being connected with the
skin by a meatus between the bands of muscle, and conveying the
thermo-barometrical impressions to the auditory nerves; hence the name of
"Wetterfisch," by which Loaches are known in some parts of Germany.
The Homalopterinae are more or less perfectly adapted to life in rapid
streams, the most remarkable in this respect being {586}_Gastromyzon_ of
North Borneo, in which the pectoral and ventral fins are much expanded to
form, with the belly, a sucker by which the fish adhere to the stones of
mountain torrents, showing a remarkable analogy to _Exostoma_ among the
Silurids.[666]
[Illustration: FIG. 355.—_Gastromyzon borneensis_, ventral view, natural
size.]
FAM. 4. SILURIDAE.—Mouth non-protractile, bordered by the praemaxillaries
and the maxillaries, or by the praemaxillaries only, the maxillaries being
often rudimentary and supporting the base of a barbel; jaws usually
toothed. Parietal bones usually confluent with the supraoccipital, forming
a single large plate (parieto-occipital); symplectic and suboperculum
absent. Pharyngeal bones normal, with small teeth. Ribs attached to the
lower surface of long parapophyses; epipleurals absent. Pectoral fins
inserted very low down, folding like the ventrals, often armed, like the
dorsal, with a strong bony spine. Body naked or with bony plates. An
adipose dorsal fin often present. One to four pairs of barbels.
The skull and the opercular apparatus show a reduction in the number of
elements as compared with the Characinids and Cyprinids, such as the
absence of the metapterygoid, the often rudimentary, rod-like condition of
the palatine, and the fusion of the parietals with the supraoccipital.[667]
The scapular arch is solidly united to the skull and is often very massive,
and the occiput may be connected with the base of the dorsal fin by a
buckler formed by the expansion of the first and second inter-neural bones.
The pterygials or supports of the pectoral rays are large and reduced to
two or three.[668] Teeth are rarely present {587}on the maxillary bones
(_Diplomystes_, _Eutropiichthys_), being usually confined to the
praemaxillaries and dentaries; they often occur on the palate. The
branchiostegal rays vary from 4 to 17. The lips are sometimes much
developed, and may form a sucking disk, as in _Euchilichthys_ and
_Exostoma_. As in the Cyprinids, the pungent spines which may arm the fins
have nothing in common with the true spines of Acanthopterygians; they
result from the co-ossification, with age, of successive articles; but,
contrary to the condition in the Cyprinids, the axis of the spine is
single, not double. The ventral rays vary from 6 to 16, 6 being the most
frequent number. Some of the exterior vertebrae may be solidly fused
together, and also with the occipito-nuchal buckler. Prof. Ramsay
Wright[669] has shown, by a study of the development, that the complex
which follows the first vertebra, which is more or less rudimentary, if
distinct, represents the fusion of the 2nd, 3rd, and 4th vertebrae, without
even nerve-foramina denoting its compound origin; the first, strongly
developed, transverse process represents that of the 4th vertebra. The
air-bladder is usually large and trilocular, but additional septa may
greatly complicate its structure, and external diverticula may also
exist;[670] it may be more or less reduced and entirely or partially
enclosed in a bilateral bony capsule formed by the transverse processes of
the vertebrae, and sometimes (_Nematogenys_) ankylosed to the skull. In a
few genera, like _Cetopsis_, the air-bladder seems to be altogether absent:
it is reduced to two small oval sacs encased in the large compound anterior
vertebra. As in Loaches, the air-bladder is often in immediate contact with
the skin behind the shoulder-girdle. The intestinal tract may be simple and
short (carnivorous forms) or extremely long and convoluted (_Callichthys_);
as in Cyprinids, pyloric appendages are absent.
Cat-Fishes, as Silurids are usually called, are a large family embracing
some 1000 species, spread over the fresh waters of all parts of the world,
but mostly from between the tropics.[671] Only a few are marine
(_Plotosus_, _Arius_, _Galeichthys_).
This family may be divided into eight subfamilies
{588}(i.) CLARIINAE.—Dorsal and anal fins very long, extending to the
caudal; gill-membranes free, or narrowly united to the isthmus.
Asiatic-African genera: _Clarias_, _Heterobranchus_, _Plotosus_.
Asiatic-Australian: _Copidoglanis_. Asiatic: _Cranoglanis_. African:
_Clariallabes_, _Allabenchelys_, _Gymnallabes_, _Channalabes_. Australian:
_Cnidoglanis_.
(ii.) SILURINAE.—Dorsal fin very short or absent, anal very long;
gill-membranes free. Europaeo-Asiatic: _Silurus_. Asiatic: _Silurodon_,
_Silurichthys_, _Saccobranchus_, _Wallago_, _Belodontichthys_,
_Cryptopterus_, _Callichrous_, _Hemisilurus_, _Ailiichthys_, _Ailia_,
_Schilbichthys_, _Laïs_, _Pseudeutropius_, _Pangasius_, _Osteogeniosus_,
_Helicophagus_, _Silondia_. African: _Eutropius_, _Schilbe_, _Siluranodon_,
_Physailia_, _Parailia_. Australian: _Eumeda_, _Neosilurus_.
(iii.) BAGRINAE.—Dorsal fin short, followed by a more or less elongate
adipose fin; anal short or moderate; gill-membranes free. Asia, Africa,
America, Australia: _Arius_. Asia and America: _Amiurus_. Asiatic:
_Macrones_, _Pseudobagrus_, _Liocassis_, _Bagroides_, _Bagrichthys_,
_Rita_, _Acrochordonichthys_, _Acysis_, _Olyra_, _Hemipimelodus_. African:
_Bagrus_, _Clarotes_, _Chrysichthys_, _Gephyroglanis_, _Auchenoglanis_,
_Notoglanidium_, _Anoplopterus_, _Galeichthys_. American: _Diplomystes_,
_Paradiplomystes_, _Aelurichthys_, _Genidens_, _Noturus_, _Callophysus_,
_Pimelodus_, _Pimelodina_, _Nanoglanis_, _Heptapterus_, _Nematogenys_,
_Pariolius_, _Pirinampus_, _Conorhynchus_, _Notoglanis_, _Callophysus_,
_Sorubim_, _Piramutana_, _Bagropsis_, _Sciades_. Australian: _Nedystoma_,
_Pachyula_.
(iv.) DORADINAE.—A short-rayed dorsal fin and an adipose, the latter
sometimes replaced by a second rayed dorsal; anal short or moderate;
gill-clefts more or less widely interrupted below. African: _Synodontis_,
_Chiloglanis_, _Atopochilus_, _Euchilichthys_, _Mochocus_, _Doumea_,
_Phractura_, _Paraphractura_, _Andersonia_, _Trachyglanis_, _Belonoglanis_.
Asiatic: _Bagarius_, _Glyptosternum_, _Gagata_, _Pseudecheneis_,
_Exostoma_, _Sisor_, _Breitensteinia_, _Sosia_, _Chaca_. South American:
_Doras_, _Oxydoras_, _Leptodoras_, _Physopyxis_, _Glanidium_,
_Centromochlus_, _Wertheimeria_, _Cetopsis_.
(v.) MALOPTERURINAE.—No rayed dorsal fin, an adipose; anal short;
gill-clefts interrupted below. African: _Malopterurus_.
(vi.) CALLICHTHYINAE.—Dorsal, anal, and adipose fins short; body completely
cuirassed; praemaxillaries much reduced, the border of the upper jaw formed
mainly by the maxillaries. South American: _Callichthys_, _Corydoras_.
{589}(vii.) HYPOPHTHALMINAE.—Dorsal fin short, behind the ventrals, anal
long; gill-clefts wide or interrupted below. South American: _Ageniosus_,
_Trachelyopterus_, _Auchenipterus_, _Epapterus_, _Tetranematichthys_,
_Hypophthalmus_, _Helogenes_.
(viii.) TRICHOMYCTERINAE.—Dorsal fin short, far back, behind the ventrals;
no adipose fin; anal short; operculum and interoperculum armed with
erectile spines. South American: _Trichomycterus_, _Eremophilus_,
_Stegophilus_, _Vandellia_, _Acanthopoma_.
Our knowledge of the distribution in time of the Silurids is still very
scanty, and throws no light on the derivation of the group. _Arius_, and
two genera apparently related to it, _Rhineaster_ and _Bucklandium_, have
left remains in the Eocene of Europe and North America, and traces of
various recent genera have been found in later Tertiary deposits in Europe,
Asia, and North and South America.
The habits of the Silurids are extremely diversified, and the shape of the
body varies accordingly. The body may be very short and the head enormous
and excessively depressed, for instance in the Indo-Burmese _Chaca
lophioides_, which, as its name implies, resembles the Fishing-Frog or
Angler; stout and _Cottus_-like in some South American _Pimelodus_;
Loach-like in _Trichomycterus_ and _Stegophilus_; more or less Eel-shaped
in _Clarias_ and its allies, etc.; the extreme of slenderness obtains in
the African _Channalabes_, the body being excessively elongate (over 100
vertebrae), the ventral fins absent, and the pectorals rudimentary or
absent. Among other remarkable forms may be mentioned the Indian _Sisor_,
which resembles _Aspredo_, and in which the upper caudal ray is much
thickened and greatly prolonged; _Pseudecheneis_, living in rapids of the
Himalayas and Khasia hills, provided with a transversely plaited ventral
disk between the pectoral fins; the African _Phractura_ and _Andersonia_,
resembling _Loricaria_; and the likewise African _Belonoglanis_, comparable
to a Needle-Fish. The spines which so frequently arm the dorsal and
pectoral fins may be barbed or serrated, and constitute formidable
defensive weapons; in the South American _Ageniosus valenciennesi_, the
maxillary bone is transformed into a strong, barbed, erectile spine,
replacing the barbel. Stings of even the smaller Cat-Fish are at least as
painful as that of a bee, and this is probably due to some poisonous
property of the dermal secretion of the Fish.
{590}[Illustration: FIG. 356.—Harmout, _Clarias anguillaris_ (after
Valenciennes). ¼ nat. size.]
Cope believed an orifice at or above the axil of the pectoral fin in
_Noturus_ to be the opening of the duct of a poison-gland; "from it may
frequently be drawn a solid gelatinous style ending in a tripod, each limb
of which is dichotomously divided into short branches of regular length." I
think this condition of things has nothing to do with a poison-organ, and
is merely a repetition of what is observed in Loaches and in the Characinid
_Xenocharax_, where I have found a gelatinous substance filling the short
duct by which the membrane of the air-bladder is placed in communication
with the skin and the sensory organ of the lateral line. Most Silurids can
live in very foul water, taking in air from the surface, and spend a
comparatively long time out of the water, without being possessed of any
special apparatus for atmospheric respiration. A few genera, however, are
provided with an accessory breathing organ: in _Clarias_, _Heterobranchus_,
and allies, there is a dendritic superbranchial organ, in _Saccobranchus_ a
long air-sac, extending from the first branchial cleft along the side of
the body, as described above, p. 295; and these Fish can live for days on
land. _Clarias lazera_ has been observed, in Senegambia, to spend several
months of the dry season in burrows, from which it emerges at night to
crawl about in search of food. Many Silurids, but especially _Doras_ and
_Synodontis_, are known to produce sounds in and out of the water by means
of a special mechanism of the air-bladder and the processes of the
vertebrae above it, combined with the movements of the pectoral spine
grinding in the glenoid cavity.[672] In South America, _Doras_ has been
observed to move rapidly on land, projecting itself forward on the pectoral
spines by the elastic spring of the tail, travelling long journeys over
land, from one drying pond to another, spending whole nights on the way;
these migrations sometimes take place {591}in numerous bands, baskets of
the small Fish being filled by the Indians who come across them.[673] The
African _Synodontis_ are much in the habit of floating or swimming
leisurely on the surface with the belly in the air, as was well known to
the ancient Egyptians, who have frequently depicted the Fish in this
anomalous position. A curious fact in connexion with this habit is that _S.
membranaceus_ and _S. batensoda_, in which it has most frequently been
observed, show an inversion of the ordinary mode of coloration, the lower
parts being dark brown or black and the upper pale silvery grey. The
electric Cat-Fish (_Malopterurus electricus_), is also a native of Africa,
occurring all over the tropical parts of that continent and also in the
Lower Nile, growing to a length of three feet. Its flesh is more esteemed
than that of other Silurids. It avoids light and is slow in its movements.
The electrical apparatus differs absolutely from that of all other Fishes,
being derived from the integument, belonging to the glandular system, and
surrounding the whole body with a thick coat of grease or gelatinous
substance; the apparatus is governed by a single nerve on each side
proceeding from a huge ganglionic cell at the anterior extremity of the
spinal cord.[674] The shocks given by _Madopterurus_ are very powerful, and
the Fish is called "Raad" by the Arabs, a name which means "thunder." Kept
in an aquarium with other Fishes, even of the same species, the "Raad" soon
kills its companions.
[Illustration: FIG. 357.—_Synodontis decorus_, from the Congo. ⅓ nat.
size.]
{592}[Illustration: FIG. 358.—_Callichthys littoralis_, from South America.
⅔ nat. size.]
In this family the eggs and young are usually looked after by the parents.
Aristotle observed that the male of the European _Silurus glanis_ watches
over and defends the eggs. In one of the commonest North American
Cat-Fishes, _Amiurus nebulosus_, a species which has been largely
introduced into some parts of Europe of late, now thriving in many ponds
and more or less polluted streams of the Continent, the eggs are deposited
near the banks of weedy ponds and rivers without currents, in concealed
places beneath logs, stumps, or even in pails or other receptacles, failing
which both parents join in excavating a sort of nest in the mud, a work
often requiring two or three days of incessant labour. The male watches
over the eggs, and later leads the young in great schools near the shore,
seemingly caring for them as the hen for her chickens.[675] The _Doras_ and
the _Callichthys_ of South America, according to Hancock[676] and
Vipan,[677] build regular nests of grass or leaves, sometimes placed in a
hole scooped out in the bank, in which they cover their eggs and defend
them, male and female sharing in this parental duty. In the likewise South
American _Corydoras_ (_Callichthys paleatus_), as observed by
Carbonnier,[678] a lengthy courtship takes place, followed by an embrace,
during which the female receives the seminal fluid in a sort of pouch
formed by the folded membranes of her ventral fins; immediately after, five
or six eggs are produced and received in the pouch, to be afterwards
carefully placed in a secluded spot. This operation is repeated many times,
until the total number of eggs, about 250, have been deposited. In
{593}accordance with these pairing habits, the pectoral spines of the male,
which are used in amplexation, are longer and stronger than those of the
female. These Fish are monogamous, and both parents remain by the side of
the nest, furiously attacking any assailant. Dr. R. Semon[679] has made
observations in Queensland on the habits of _Arius australis_, which builds
nests in the sandy bed of the Burnett River. These nests consist of
circular basin-like excavations, about 20 inches in diameter, at the bottom
of which the eggs are laid, and covered over by several layers of large
stones. A still more efficient protection is afforded their progeny by the
marine and estuarine species of _Arius_,[680] _Galeichthys_,[681] and
_Osteogeniosus_,[682] the male, more rarely the female, carrying the eggs
in the mouth and pharynx; these eggs, few in number, are remarkably large,
measuring as much as 17 or 18 millimetres in diameter in _Arius
commersonii_, a Fish of three or four feet in length. According to
Babuchin, _Malopterurus_ also is said by the Nile fishermen to shelter its
fry in the mouth.
Some of the Silurids attain to a very large size. Among these is the type
of the family, _Silurus glanis_, the "Wels" of the Germans, its only
European representative, which occurs over a great part of Europe, but is
absent from the British Isles, France, the Spanish Peninsula, and Italy. It
is most abundant in the Danube basin, where it sometimes reaches a length
of 10 feet or more and a weight of 400 lbs. It is the largest strictly
fresh-water Fish of Europe. Among the smallest species, we have to mention
the "Candiru" of Brazil, _Vandellia cirrhosa_, 60 millimetres in length and
3 or 4 in diameter, which is believed to enter and ascend the urethra of
people bathing, being attracted by the urine; the Fish, having once made
its way into the urethra, cannot be pulled out again, owing to the erectile
spines which arm its gill-covers. The natives of some parts of the Amazons
are in great dread of this Fish, and protect themselves when entering the
water by wearing a sheath formed of a small, minutely-perforated
cocoanut-shell suspended from a belt of palm-fibres.[683] According {594}to
Reinhardt[684] the allied _Stegophilus insidiosus_, a small colourless
Fish, 30 to 40 mm. long, from Brazil and Argentine, lives parasitically in
the gill-cavity of large Cat-Fishes (_Platystoma_). Dr. F. Silvestri has
noticed that it sucks the blood in the gills of _Platystoma coruscans_, a
Silurid growing to a length of 6 feet.
[Illustration: FIG. 359.—Upper view of heads of _Chaetostomus cirrhosus_,
male and female. (Nat. size.)]
FAM. 5. LORICARIIDAE.—Distinguished from the preceding by the sessile ribs
and the absence of the transverse processes in the praecaudal vertebrae,
which have bifid neural spines. The air-bladder is always much reduced, and
enclosed in a right and a left bony capsule formed by the skull and the
anterior vertebrae. Gill-openings narrow clefts. The mouth is inferior,
with more or less developed circular lips and feeble dentition; it is used
as a sucker, by which the Fish fixes itself to any hard object with such
strength that it cannot be pulled off without great difficulty. The teeth
are usually slender and bicuspid. The food consists of very small prey and
more or less putrefied organic substances, the intestine being usually
extremely elongate and much convoluted. The habits of these Fish are very
little known, but the fact that the males of many species have the pectoral
fins much stronger than the females renders it probable that they pair like
{595}_Callichthys_. There are other sexual differences in many species of
_Plecostomus_, _Chaetostomus_, and _Loricaria_, as the presence of dermal
tentacles on the snout (see Fig. 359), or of hair-like bristles on various
parts of the head and fins in the males, which are usually of larger size.
About 200 species are known, all from the tropical and subtropical parts of
Central and South America. The largest species (_Chaetostomus gigas_)
measures 2½ feet; many are of very small size.[685] The genera may be
referred to two sub-families:—
(i.) ARGINAE.—Body naked; ribs strong. _Arges_, _Stygogenes_,
_Astroblepus_.
(ii.) LORICARIINAE.—Body cuirassed by bony plates; ribs very slender.
_Plecostomus_, _Liposarcus_, _Chaetostomus_, _Cochliodon_,
_Pterygoplichthys_, _Rhinelepis_, _Acanthicus_, _Otocinclus_,
_Hypoptopoma_, _Loricaria_, _Acestra_.
[Illustration: FIG. 360.—_Acestra gladius_, from the Jurua River, with
upper and lower views of head and trunk. (⅔ nat. size.)]
The "Prenadillas" of the Andes, _Arges_ and _Stygogenes_, were believed to
live in subterranean waters within the bowels of active volcanoes, and to
be ejected with streams of mud and water during eruptions, a story that has
been repeated by Humboldt. The fact is that they live in small torrents at
great altitudes (up to 10,700 feet), and are swept down during periods of
disturbance caused by the eruption of the volcano.[686] The members of the
sub-family Loricariinae vary much in the shape of the body, which may be
short and stout, or more or less slender, the extreme in the latter respect
being attained by the species of the genus _Acestra_.
{596}FAM. 6. ASPREDINIDAE.—This family is also closely related to the
Siluridae. The ribs are sessile as in the Loricariidae, but inserted very
low down on the centra, which higher up bear strong transverse processes.
The opercular bone is entirely absent. The gill-opening is reduced to a
foramen in front of the pectoral fin. The head is extremely depressed and
the mouth terminal; the tail is very slender; the body is naked. The
air-bladder is large and free, the intestinal canal short. Four genera from
South America: _Aspredo_, _Bunocephalus_, _Bunocephalichthys_,
_Dysichthys_. Species 18. _Aspredo_, of the Guianas, the largest form,
reaching to about a foot in length, is remarkable for the manner in which
the female carries her eggs. The skin of the lower parts assumes a spongy
condition about the breeding season, and the eggs, after being deposited,
become attached to the lower surface of the head, belly, and paired fins,
forming a single layer; each egg becomes connected with the skin of the
mother by a cup-shaped, pedunculate base, supplied with blood-vessels and
coated with a layer of epithelium, the formation of which is still
unexplained.[687]
{597}CHAPTER XXII
TELEOSTEI (_CONTINUED_): SYMBRANCHII—APODES—HAPLOMI—HETEROMI—CATOSTEOMI—
PERCESOCES—ANACANTHINI
SUB-ORDER 3. SYMBRANCHII
Eel-shaped Fishes without paired fins, with the pectoral arch free or
suspended from the skull, and with the anterior vertebrae distinct, without
Weberian ossicles. Gill-openings confluent into a single, ventral slit.
Air-bladder absent.
The structure of the skull conforms to that of typical Malacopterygians.
The praemaxillary and maxillary are well developed, the latter placed
behind the former, and forming but a very small part of the oral border;
the symplectic is present; the parietals form a long sagittal suture, and
separate the frontals from the supraoccipital. The vertebrae are very
numerous, the praecaudal bearing very strong parapophyses, to which short,
slender ribs are attached. The skin is naked (Symbranchidae) or covered
with minute scales (Amphipnoidae), and the vertical fins are rudimentary,
reduced to mere dermal folds.
Like the Apodes, which they resemble in general appearance, these Fishes
are no doubt derived from some low type with abdominal ventral fins, but
whether from the Malacopterygii or the Haplomi we have as yet no data from
which to conclude. Only two families are known.
FAM. 1. SYMBRANCHIDAE.—Post-temporal well developed, forked, attached to
the skull. Inhabitants of the fresh or brackish waters of South-Eastern
Asia, Tropical America, Australia, and Tasmania. Three genera are known:
_Symbranchus_, with two species from India and the Malay region, and one
from Central and South America; _Monopterus_, with a single species
{598}from China, Japan, and the Malay region; and _Chilobranchus_, with two
species from Australia and Tasmania. Although the South American
_Symbranchus_ has been observed to live in marshes which periodically dry
up, the Fish burying itself in the mud like a _Lepidosiren_, the branchiae
are fully developed on the four branchial arches. In _Monopterus_, of
similar habits, the branchial laminae are rudimentary, and on three arches
only. No accessory breathing organ is known to exist.
[Illustration: FIG. 361.—_Monopterus javanensis_. Lower view of head,
showing gill-opening (_go_): lower view of middle praecaudal vertebrae: and
side view of skull and pectoral arch. _ar_, Articular; _br_, branchiostegal
rays; _bra_, branchial arches; _cl_, clavicle; _d_, dentary; _eot_,
epiotic; _eth_, ethmoid; _f_, frontal; _hm_, hyomandibular; _iop_,
interoperculum; _m_, maxilla; _mpt_, metapterygoid; _n_, nasal; _op_,
operculum; _p_, parietal; _pm_, praemaxilla; _pop_, praeoperculum; _ppt_,
pterygopalatine; _ptte_, post-temporal; _q_, quadrate; _scl_,
supra-clavicle; _so_, supra-occipital; _sop_, suboperculum; _sq_,
squamosal; _sy_, symplectic.]
FAM. 2. AMPHIPNOIDAE.—Post-temporal absent, the shoulder-girdle free from
the skull. The Cuchia, _Amphipnous cuchia_, the sole representative of this
family, an inhabitant of the fresh and brackish waters of India and Burma,
growing to two feet in length, is remarkable for the presence of a
respiratory air-sac on each side of the neck behind the head, communicating
with the gill-cavity. Of the three branchial arches the second alone
possesses gill-filaments; the third supports, in their place, a thick and
semi-transparent tissue; the principal organs of respiration are two small
bladders, resembling the posterior portions of the lungs of snakes, which
the animal has the power {599}of filling with air immediately derived from
the atmosphere. Although covered over by the common integuments, these
bladders present externally, when inflated, two protuberances of a round
shape. Of the whole volume of blood contained in the branchial artery,
one-third passes through the gills and respiratory bladders, whilst the
other two-thirds are conveyed directly from the heart to the aorta without
being exposed to the action of the air.[688] This amphibious Fish, when in
the water, constantly rises to the surface for the purpose of respiration,
and it is often found lying in the grassy sides of ponds after the manner
of Snakes.
SUB-ORDER 4. APODES.
Air-bladder, if present, communicating with the digestive tract by a duct.
Praemaxillaries absent; the maxillaries, if present, separated on the
median line by the coalesced ethmoid and vomer. Pectoral arch, if present,
not connected with and remote from the skull; mesocoracoid arch absent.
Fins without spines, the ventrals absent. Anterior vertebrae distinct,
without Weberian ossicles.
The Apodes or Eels are elongate, serpentiform Fishes with naked skin, or
with minute scales imbedded in the skin, the opercular bones small and
completely hidden under the integument; narrow or minute gill-openings; the
vertical fins, if present, confluent behind or separated by the projecting
tip of the tail. The pterygo-palatine arch is often reduced or absent, and
there is no distinct symplectic; the supraoccipital bone is small,
separated from the frontals by the parietals, which meet on the middle
line. The vertebrae are very numerous (up to 225), and the praecaudals bear
strong parapophyses, to which short, slender ribs may be attached;
epineurals are sometimes present. The five families into which this
sub-order is divided show remarkable degrees of simplification of the
skull, through reduction or loss of either the maxillary or the
pterygo-palatine arches.
There has been much difference of opinion in the determination of the bones
of the upper jaw in these Fishes. Cuvier regarded the lateral bones of the
upper jaw as praemaxillaries, Owen and Richardson as palatines (at least in
Muraenas), whilst Peters {600}and most recent authors have identified them
throughout the order as maxillaries.[689] The conclusion I have come to
from the examination of numerous skulls belonging to various genera, is
that the praemaxillaries have disappeared in all, whilst the maxillaries
have persisted in the true Eels (Anguillidae) and disappeared in the
Muraenidae, their place being taken by the fused palato-ectopterygoids,
which may even join the mandibular suspensorium. The vestigial bone,
regarded by Jacoby as the pterygoid in _Muraena helena_, may be identified
as the meta-pterygoid, and therefore does not disprove the homology, here
suggested, of the other elements of the palate.
FAM. 1. ANGUILLIDAE.—Maxillaries present, separated on the median line by
the ethmo-vomer; palato-pterygoid bone present, connected with the
hyomandibular and quadrate; gill-clefts separate, opening into the pharynx
by wide slits; tongue present; vent far removed from the head.
[Illustration: FIG. 362.—Skull and pectoral arch of _Conger vulgaris_, side
view. _Ar_, Articular; _br_, branchiostegal rays; _ch_, ceratohyal; _cl_,
clavicle; _cor_, coracoid; _d_, dentary: _eot_, epiotic; _eth_, ethmoid;
_f_, frontal; _hm_, hyomandibular; _iop_, interoperculum; _m_, maxilla;
_n_, nasal; _op_, operculum; _p_, parietal; _pop_, praeoperculum; _por_,
praeorbital; _ppt_, pterygo-palatine; _ps_, parasphenoid; _ptf_,
post-frontal; _ptr_, pterygials; _q_, quadrate; _sc_, scapula; _scl_,
supra-clavicle; _so_, supra-occipital; _sop_, suboperculum; _sq_,
squamosal; _uh_, urohyal; _v_, vomer.]
Spread over all the seas of the temperate and tropical zones, often
descending to the greatest depths, a few entering fresh waters. Many are
known to undergo very striking metamorphoses, the pellucid, strongly
compressed larvae (_Leptocephalus_) having long been a puzzle to
naturalists.
{601}Nearly 150 recent species are known, of which some 50 are deep-sea
forms, occurring down to 2500 fathoms. Scanty fossil remains, referable to
recent genera or scarcely different from them, are known from the Eocene of
Europe. The Cretaceous genus _Urenchelys_, from England and the Lebanon, is
interesting as representing a more generalised type, the hindmost vertebrae
bearing a pair of expanded hypural bones, showing the diphycercal Eels to
have been derived from Fishes with a normal caudal fin.
The genera are numerous. The following are the principal:—_Anguilla_,
_Simenchelys_, _Ilyophis_, _Conger_, _Coloconger_, _Congromuraena_,
_Uroconger_, _Heteroconger_, _Muraenesox_, _Nettastoma_, _Nettophichthys_,
_Saurenchelys_, _Nettenchelys_, _Myrus_, _Myrophis_, _Derichthys_,
_Chilorhinus_, _Muraenichthys_, _Liuranus_, _Ophichthys_, _Moringua_.
In the first four genera, small, more or less lineal rudimentary scales are
embedded in the skin, arranged in small groups, which are placed obliquely
at right angles to one another, forming a curious pattern; but these scales
are so small that they escape the notice of the superficial observer, hence
Eels have been improperly included among the Fishes forbidden as food by
the Mosaic prescriptions. In the other genera, including the exclusively
marine Conger of our coasts, scales are really absent.
The Common Eel (_Anguilla vulgaris_) has a very wide distribution, being
found over the greater part of Europe, North Africa, Temperate Asia, and
perhaps also North America east of the Rocky Mountains, Mexico, and the
West Indies. Its record from Australia and New Zealand is probably due to
the imperfection of our knowledge of the specific characters. It is not
found in the Black Sea nor in the rivers flowing into it, owing, no doubt,
to the sulphurous nature of the bottom of the sea, to which, as we now
know, these Fish would have to resort for breeding.
The mode of propagation of the Eel long remained a mystery, from the fact
that individuals found in fresh water never show ripe genital glands. The
idea had been entertained of their being hermaphrodite, and internal
parasites had also given rise to the belief in their viviparous nature. The
genital glands of the female were first investigated by Rathke in 1838, but
it was not until 1874 that those of the male were discovered by Syrski, and
shortly after fully described by L. Jacoby, who, in his final contribution
to the subject, concluded that Eels need salt water for the development of
their organs of generation, and that this development takes place, not near
the coast, but further out in deep water.
{602}[Illustration: FIG. 363.—Larva of Common Eel, _Leptocephalus
brevirostris_ of Kaup. (After Kaup.)]
As a rule it is not until the fifth or sixth year that the Eels go to the
sea for the purpose of propagation, which takes place at great depths—at
least 200 fathoms. Males have been observed to precede the females. The
breeding season over, the Eels do not return to fresh waters, but are
believed to die soon after. The eggs were discovered by Raffaele in 1888 in
the Gulf of Naples, and shortly after Grassi and Calandruccio finally
settled the question of the breeding and development of the Fish from
observations made in the Mediterranean. Their conclusions are thus summed
up:—"The Common Eel matures in the depths of the sea, where it acquires
larger eyes than are ever observed in individuals which have not yet
migrated to deep water. The abysses of the sea are its spawning places; its
eggs float in the sea water. In developing from the egg, it undergoes a
metamorphosis, it passes through a larval form denominated _Leptocephalus
brevirostris_." What length of time the development requires is not yet
fully established, since the Leptocephali are rarely found at the surface,
most of the specimens studied by Grassi and Calandruccio having been
obtained from the stomach of the Sun-Fish (_Orthagoriscus mola_) in the
Straits of Messina; but it is believed that the young Eels or "elvers,"
which ascend our rivers in such prodigious numbers in spring and summer
("Eel-Fares") are already one year old. Some individuals apparently spend
their whole life in fresh waters, but they are barren.[690] A specimen was
kept in confinement in the family of the French naturalist Desmarest for
upwards of 40 years, growing to a length of 4½ feet, being already of large
size at the time of {603}its capture. Eels are extremely voracious, and
endowed with an extraordinary tenacity of life; they can live for many
hours out of the water, and are often met with at night creeping through
the grass of meadows from one pond or stream to another.
One of the most remarkable among the deep-sea Eels is the Snub-nosed Eel
(_Simenchelys parasiticus_), which has been found in great numbers off
Newfoundland and the Azores, at depths of 200 to 900 fathoms. The maxillary
and mandibular bones are very short and massive, provided with large obtuse
teeth; the head is short and bulldog-like in aspect, the mouth small and
bordered by a thick circular lip. Some specimens have been observed to
burrow in the muscles of living Halibut and other large Fishes, after the
manner of _Myxine_.
FAM. 2. NEMICHTHYIDAE.—Distinguished from the preceding by the position of
the vent, which is close to, or at no great distance from, the
gill-openings. The rays of the vertical fins are connected by thin membrane
instead of being imbedded in thick skin, as in most Eels; in some of the
genera the jaws are excessively prolonged, needle-like, sometimes recurved.
Deep-sea Eels of small size, represented in the Atlantic, Pacific, and
Indian Oceans by about 10 species, referred to 6 genera: _Dysomma_,
_Dysommatopsis_, _Nemichthys_, _Spinivomer_, _Serrivomer_, _Gavialiceps_.
FAM. 3. SYNAPHOBRANCHIDAE.—Maxillaries narrowly separated on the median
line, their extremity strongly attached by ligament to the mandible;
pterygo-palatine arch absent. Gill-openings externally confluent into a
single ventral slit. Deep-sea Fishes, resembling the true Eels in the
general form and in the presence of linear scales placed at right angles,
but differing in the absence of the pterygo-palatine arch, as in the
Saccopharyngidae. Eight species of _Synaphobranchus_ are known, from the
Atlantic, Pacific, and Indian Oceans, at depths of 200 to 2000 fathoms.
FAM. 4. SACCOPHARYNGIDAE.—Maxillaries narrowly separated on the median
line, extremely elongate; mouth enormous; pterygo-palatine arch absent;
hyomandibular arch slender and movably articulated to the cranium, the two
bones (hyomandibular and quadrate) of which it is composed being capable of
being swung in all directions; branchial arches far behind the skull; no
branchiostegal rays or pharyngeal bones.
Extraordinary-looking deep-sea Fishes allied to the Eels, of which they
appear to be a further degraded type, the muscles {604}being feebly
developed and the skeleton imperfectly calcified. The mouth, furnished with
rather long but feeble, or even minute teeth, and the pharynx and stomach
are capable of great distension, these Fish being able to get outside a
prey very much larger than themselves; the eyes are situated far forward on
the head; the tail is extremely slender and elongate. Four genera are
known, each with a single species, from the Atlantic: _Saccopharynx_,
_Eurypharynx_, _Macropharynx_, and _Gastrostomus_. The depths at which they
have been obtained vary between 389 and 1467 fathoms, but three out of the
four known specimens of _Saccopharynx_ were brought to the surface by
having swallowed a Fish too large for the capacity of the stomach. The
length of the largest specimen is about 6 feet, of which the tail
constitutes nearly three-fourths.
[Illustration: FIG. 364.—_Saccopharynx ampullaceus_, ⅓ nat. size. (After
Günther.)]
[Illustration: FIG. 365.—Skull of _Thyrsoidea meleagris_, side view, _ar_,
Articular; _d_, dentary; _eot_, epiotic; _eth_, ethmoid; _f_, frontal;
_hm_, hyomandibular; _iop_, interoperculum; _n_, nasal; _op_, operculum;
_os_, orbitosphenoid; _p_, parietal; _pop_, praeoperculum; _por_,
praeorbital; _ppt_, pterygo-palatine; _ps_, parasphenoid; _ptf_,
post-frontal; _q_, quadrate; _so_, supraoccipital; _sop_, suboperculum;
_sor_, suborbitals; _sq_, squamosal; _v_, vomer.]
FAM. 5. MURAENIDAE.—Maxillaries absent, replaced by the palato-pterygoid,
the mouth bordered by the latter and the {605}ethmo-vomer; palato-pterygoid
bone separated from hyomandibular arch; branchial openings into the pharynx
narrow slits; no tongue.
The body is naked, pectoral fins are usually absent, and the gill-cleft is
a small round opening. The opercular bones are much reduced in size, and
the pectoral arch may be totally absent.
Voracious marine Fishes, inhabiting tropical and subtropical waters, being
especially abundant about coral reefs. Some 120 species are known, many
reaching a very large size, and being also remarkable for their variegated
coloration. The genera are mostly founded on the dentition, which shows
much diversity; the following are the principal:—_Myroconger_,
_Enchelycore_, _Muraena_, _Thyrsoidea_, _Lycodontis_, _Pythonichthys_,
_Echidna_, _Channomuraena_. The Muraena of the ancient Romans, _Muraena
helena_, of the Mediterranean, Eastern Atlantic, and neighbouring parts of
the Indian Ocean, occurring exceptionally as far north as the English
coast, grows to 4 feet, and its flesh was more esteemed than that of any
other Fish, large numbers being reared in specially constructed reservoirs
near the sea, and fed on the corpses of slaves. _Channomuraena vittata_,
from the coast of Cuba, is known to attain a length of 8 feet, and
_Thyrsoidea macrura_, from the Indian Ocean and the Malay Archipelago, to
upwards of 10 feet.
SUB-ORDER 5. HAPLOMI.
Air-bladder, if present, communicating with the digestive tract by a duct.
Opercle well developed. Pectoral arch suspended from the skull; no
mesocoracoid arch. Fins usually without, rarely with a few spines; ventrals
abdominal, if present. Anterior vertebrae distinct, without Weberian
ossicles.
The absence of the mesocoracoid arch distinguishes the Haplomi from the
Malacopterygii, with which they are united by various authors. They lead to
the Percesoces through the Cyprinodontids, and to the Lower
Acanthopterygians, such as the Berycidae, through the Scopelids,
Stephanoberycids, and Percopsids, as is evidenced by the structure of the
mouth and the forward position, in some of the genera, of the ventral fins,
which, however, are never attached to the pectoral girdle. Most of the
forms which are here included inhabit either fresh water or the deep sea.
{606}SYNOPSIS OF THE FAMILIES.
I. Parietals separating the frontals from the supraoccipital; post-
temporal simple; praecaudal vertebrae with autogenous parapophyses.
Margin of the upper jaw formed by the praemaxillaries and the
maxillaries; basis cranii simple; no adipose dorsal fin
1. _Galaxiidae_.
Margin of the upper jaw formed by the praemaxillaries only; basis
cranii double; adipose dorsal fin present 2. _Haplochitonidae_.
II. Frontals in contact with the supraoccipital.
A. Praecaudal vertebrae without parapophyses.
1. Margin of the upper jaw formed by the praemaxillaries and the
maxillaries.
Body without or with minute scales, usually with rows of scutes;
adipose dorsal fin usually present 3. _Enchodontidae_.†
Body scaly; post-temporal forked; no adipose dorsal fin; ventrals
with 6 to 11 rays 4. _Esocidae_.
Body scaly; post-temporal incompletely ossified; pectoral fin
without pterygials; no adipose dorsal fin; ventrals with
3 rays only 5. _Dalliidae_.
2. Maxillaries excluded from the oral border.
a. Adipose dorsal fin usually present; ventral fin with 7 to
10 rays.
Post-temporal forked; dorsal fin formed of articulated rays
6. _Scopelidae_.
Post-temporal simple; dorsal fin very long, formed of slender,
non-articulated, simple or bifid rays 7. _Alepidosauridae_.
b. No adipose dorsal fin; head and mouth enormous, dentition
feeble; body naked; ventral fins, if present, with 5 rays
8. _Cetomimidae_.
B. Praecaudal vertebrae with well-developed parapophyses; maxillaries
excluded from the oral border.
1. Dorsal and anal fins without spines; scales cycloid, or with
erect spines; no adipose fin.
Mouth not protractile; ventral fins far forward, with 7 to
17 rays 9. _Chirothricidae_.†
Mouth not protractile; ventral fins remote from the pectorals,
with 9 rays 10. _Kneriidae_.
Mouth protractile; ventral fins, if present, with 5 to 7 rays
11. _Cyprinodontidae_.
Mouth scarcely protractile; ventral fins rudimentary or absent;
vent close to the gills 12. _Amblyopsidae_.
Mouth slightly protractile; ventral fins with 5 or 6 rays
13. _Stephanoberycidae_.
2. Dorsal and anal fins with true spines; scales ctenoid; an
adipose dorsal; ventral fins with 9 rays 14. _Percopsidae_.
† Fossil only.
{607}FAM. 1. GALAXIIDAE.—Margin of the upper jaw formed by the
praemaxillaries and the maxillaries, the latter behind the former, and
toothless. Parietals in contact with each other, and separating the
frontals from the supraoccipital; opercular bones all well developed. Basis
cranii simple. Ribs inserted on strong, autogenous parapophyses;
epipleurals and epineurals. Post-temporal simple, attached to the epiotic;
post-clavicle present. Body naked. Vertical fins far back; no adipose
dorsal fin. Pectoral fins inserted very low down. Ventrals, if present,
with seven rays. Air-bladder present. Ova falling into the cavity of the
abdomen before exclusion.
[Illustration: FIG. 366.—_Galaxias brevipinnis_, from New Zealand, ½
natural size.]
[Illustration: FIG. 367.—Distribution of the Galaxiidae.]
The genus _Galaxias_ has an interesting distribution, the species of which
it is made up occurring in the fresh waters of the southern hemisphere,
viz. 8 in New Zealand and neighbouring islands, 7 in New South Wales, 3 or
4 in South Australia, 1 in West Australia, 2 in Tasmania, 7 in South
America, from Chili southwards, and 1 at the Cape of Good Hope. One species
(_G. attenuatus_) is even believed to be identical in New Zealand,
Tasmania, South Australia, the Falkland Islands, and South America. This
conclusion is probably correct from the fact, which may account for the
distribution of the whole genus, {608}that it is not confined to fresh
waters, but occurs also in the sea. Specimens were observed by Mr. Rupert
Vallentin in the Falkland Islands, where the Fish is known to the
inhabitants as "Smelts," in shoals in the shallow water along the shore;
and, according to Mr. F. E. Clarke, the same species, in New Zealand,
periodically descends to the sea, where it spawns, from January to March,
and returns from March to May. A marine species has recently been
discovered at the Chatham Islands. In New Zealand, the _Galaxias_ were
called "Trout" by the settlers before the introduction of Salmonids, whilst
the fry of _G. attenuatus_ are eaten as "Whitebait." The largest species
reach the length of a foot. _Neochanna_, from New Zealand, differs from
Galaxias in the absence of ventral fins; it has been found in burrows,
which it excavates at a distance from water.
FAM. 2. HAPLOCHITONIDAE.—Small fresh-water Trout-like Fishes, agreeing in
most respects with the Galaxiidae, to which they are unquestionably closely
related, differing only in the greater extent of the praemaxillaries, which
exclude the maxillary from the oral border, in the double basis cranii (the
prootics uniting under the brain, leaving a canal between them and the
parasphenoid), in the shorter parapophyses, which, like the neural arches
of the praecaudal vertebrae, are autogenous, and in the presence of a small
adipose dorsal fin, opposed to the anal.
Two genera: _Haplochiton_, naked, with a single species from Chili, the
southern extremity of South America, and the Falkland Islands, and
_Prototroctes_, covered with small scales, of which one species inhabits
Queensland, another South Australia, and a third New Zealand. In
_Haplochiton_, the urogenital orifice of both sexes is produced into a
cylindrical tube, which lies concealed in a groove in front of the anal
fin.
FAM. 3. ENCHODONTIDAE.—Margin of the upper jaw formed by the
praemaxillaries and the maxillaries, the latter sometimes toothed like the
former. Frontals in contact with the supraoccipital; basis cranii simple.
Ribs sessile; praecaudal vertebrae without transverse processes. Rayed
dorsal fin never much extended; sometimes an adipose fin behind it. Scales
delicate or absent, but occasional longitudinal series of scutes occur, the
dorsal series, when present, being unpaired.
Cretaceous Fishes allied to, and apparently more generalised than, the
Esocidae and Scopelidae. Numerous remains from {609}Europe and North
America, referred to 7 genera: _Enchodus_, _Eurypholis_, _Palaeolycus_,
_Halec_, _Cimolichthys_, _Prionolepis_.
FAM. 4. ESOCIDAE.—Margin of the upper jaw formed by the praemaxillaries and
maxillaries, the latter behind the former, and toothless. Supraoccipital in
contact with the frontals, separating the small parietals; opercular bones
all well developed; basis cranii simple. No parapophyses, except to the
hindermost praecaudal vertebrae; epipleurals and epineurals. Post-temporal
forked, the upper branch attached to the epiotic, the lower to the
exoccipital; post-clavicle present. Vertical fins far back; no adipose
dorsal fin. Pectoral fins inserted very low down; ventrals with 6 to 11
rays. Air-bladder present.
As in the Haplochitonidae, the neural and haemal arches are bones distinct
from the centra, and although parapophyses are not developed, the ribs are
not inserted on the centra, but on distinct bases wedged into the
latter.[691] Teeth are present on the vomer, palatine, and pharyngeal
bones.
[Illustration: FIG. 368.—Skeleton of _Esox lucius_. (After Jordan and
Evermann.)]
A small family of carnivorous freshwater Fishes, including the Pike
(_Esox_), of predaceous habits, unsurpassed in greediness and voracity, and
the small and insignificant-looking _Umbra_, distinguished by the more
anterior position of the dorsal fin, the larger scales, and the moderately
large gape, with feeble villiform teeth. The range of the Esocidae is
restricted to the cold and temperate parts of the northern hemisphere.
Besides the well-known _Esox lucius_ of Europe, Northern Asia, and the
northern parts of North America, growing to a length of 4 feet, and the
Maskinongy (_E. nobilior_) of north-eastern North America, reaching twice
that length, the first genus comprises three smaller species from the
Eastern United States. Remains of _Esox_ have been found in {610}various
freshwater deposits in Europe as far back as the Oligocene. _E. lepidotus_,
of which very perfect specimens have been found in the Upper Miocene beds
of Oeningen in Baden, differs from the living species in its much larger
scales and in the greater approximation of the ventral and anal fins, two
characters in which it approaches _Umbra_. Only two species of the latter
are known: _U. crameri_ ("Hundsfisch"), from the stagnant waters of
Austria-Hungary, and _U. limi_ ("Mud-Fish"), living in swamps and ditches
in Canada and the north-eastern United States, often remaining imbedded in
the mud of prairie sloughs and bog-holes.
[Illustration: FIG. 369.—Distribution of the Esocidae.]
FAM. 5. DALLIIDAE.—The genus _Dallia_, with a single species inhabiting the
streams and ponds of Alaska and Siberia, is related to _Umbra_, but differs
in the very thin and papery skeleton, with the post-temporal imperfectly
ossified and the pectoral fin without pterygials or actinosts. The dorsal
fin is far back and opposite to the anal, as in the Pike. The ventral fins
are composed of three rays only, and the pectorals, which have a somewhat
fleshy base, have as many as 36. The scales are extremely small, and partly
imbedded in the skin. The Black-Fish, _D. pectoralis_, abounds in Sphagnum
ponds, feeding on plants and worms, and forming the chief food of the
natives of some parts of Northern Alaska, where, with the exception of the
Salmonids, it is the only freshwater Fish. Turner, its discoverer, says its
vitality is {611}extraordinary: Black-Fishes will remain frozen in baskets
for weeks, and when thawed are as lively as ever, one having been swallowed
in a congealed condition by a dog, thawed out by the heat of the stomach,
and vomited up alive.
[Illustration: FIG. 370.—_Dallia pectoralis_, ½ natural size. (After L. M.
Turner.)]
FAM. 6. SCOPELIDAE.—Praemaxillaries much elongate, and completely excluding
the maxillaries from the oral border. Supraoccipital in contact with the
frontals, sometimes partly covered by the parietals; opercular bones all
well developed. Basis cranii simple. Ribs sessile; no parapophyses on the
praecaudal vertebrae; epipleurals and epineurals. Post-temporal forked, the
upper branch in contact with the epiotic or the supraoccipital, the lower
with the opisthotic; post-clavicle present. An adipose dorsal fin often
occurs; luminous spots often present on head and body. Ventral fins with 7
to 10 rays. Air-bladder sometimes absent.
A large family (over 100 known living species), mostly of pelagic and
deep-sea Fishes. A great number of fossil types have been described.
Recent genera:
A. Without photophores: _Saurus_, _Saurida_, _Bathysaurus_, _Harpodon_,
_Scopelarchus_, _Aulopus_, _Odontostomus_, _Omosudis_, _Sudis_,
_Paralepis_, _Bathypterois_, _Benthosaurus_, _Chlorophthalmus_, _Ipnops_.
B. With photophores: _Scopelus_, _Dasyscopelus_, _Neoscopelus_,
_Scopelengys_, _Nannobrachium_, _Scopelosaurus_.
Fossil genera:
A. Cretaceous: _Sardinioides_, _Acrognathus_, _Leptosomus_, _Sardinius_,
_Dactylopogon_, _Nematonotus_, _Microcoelia_, _Opisthopteryx_, _Apateodus_,
_Rhinellus_. B. Eocene, Oligocene, and Miocene: _Omiodon_, _Scopeloides_,
_Parascopelus_, _Anapterus_.
{612}[Illustration: FIG. 371.—A, _Scopelus crocodilus_ (after Goode and
Bean). B, _Bathypterois dubius_ (after Collett). C, _Ipnops murrayi_, with
dorsal view of head (after Goode and Bean).]
{613}The members of this Family vary much in form, and among them are to be
found some of the most curious adaptations to bathybial existence. One of
the best known is _Harpodon nehereus_, which, when newly taken, is
brilliantly phosphorescent all over the body; in a salted and dry condition
it is the "Bombay-duck," a delicacy eaten with curries, and exported in
large quantities from the west coast of India. It is not known to occur at
any great depth, and is not even restricted to the sea, being very abundant
in the rivers and estuaries of Bengal and Burma; whilst an allied species,
_H. squamosus_, is found in the Indian Ocean at depths of 120 to 300
fathoms. In _Bathypterois_, the eyes are very small; some of the rays of
the paired fins being excessively prolonged, acting as tactile organs, and
compensating the reduction in the eyes. Sir John Murray has observed about
_B. longipes_: "When taken from the trawl [from 2650 fathoms] they were
always dead, and the long pectoral rays were erected like an arch over the
head, requiring considerable pressure to make them lie along the side of
the body; when erected they resembled Pennatulids like _Umbellula_." In
_Ipnops_, which resembles in general form the large-eyed _Chlorophthalmus
gracilis_, the upper surface of the broad spatulate snout is occupied by a
luminous organ longitudinally divided into two symmetrical halves, and the
eyes are absent, unless, as first supposed, this extraordinary organ be a
modification of them; but Professor Moseley's examination seems to have
proved beyond doubt that it is a special form of phosphorescent organ, the
object of which would be to attract other creatures to the wide gape of a
Fish which, living in the abysses of the sea and deprived of organs of
sight and touch, would have great difficulty in procuring its food.
_Odontostomus_, with a very large eye which can be turned upwards and
sidewards, and enormous compressed curved teeth, barbed at the tip and
depressible backwards, is one of the few Scopelids in which scales are
completely absent.
The numerous species (about 50) of _Scopelus_ and their allies are
moderate-sized or small pelagic and deep-sea forms found in nearly all the
seas, some coming to the surface at night, whilst others are confined to
great depths; they are remarkable for the series of phosphorescent spots
(photophores) on the body, and in some species also on the head, where they
may form large patches on the snout. The arrangement of these photophores
is a very {614}definite one, and it has been used for the division of these
Fishes into genera or sub-genera.[692] The ventral fins have a more forward
position than in most other members of the Family.
FAM. 7. ALEPIDOSAURIDAE.—Characters as in the preceding, but supratemporal
simple, attached to the opisthotic, and dorsal fin very long, formed of
slender, non-articulated, simple or bifid rays, extending along nearly the
whole length of the back, followed by a small adipose fin. The air-bladder
is absent and the body scaleless. The skeleton is feebly ossified; the
dentition is very powerful, some of the teeth on the palate and mandible
being very strongly enlarged. 4 or 5 species are known, from considerable
depths in the Atlantic and Pacific Oceans, referable to one genus,
_Alepidosaurus_ or _Plagyodus_. _A. ferox_, from the Atlantic, reaches a
length of 4 feet.
[Illustration: FIG. 372.—_Alepidosaurus ferox_, ⅑ nat. size. (After Goode
and Bean.)]
FAM. 8. CETOMIMIDAE.—The affinities of the recently discovered genera
_Rondeletia_ and _Cetomimus_, deep-sea Fishes from the North Atlantic, at
depths of 1000 to 1600 fathoms, are still uncertain, as the skeleton could
not be examined; they are probably most nearly related to the Scopelidae.
The head is enormous, with very wide gape, that of _Cetomimus_ being
suggestive of that of a Right Whale; the teeth are small and coarsely
granular; the gill-openings are very wide; the body is more or less
compressed and scaleless; the dorsal and anal fins are opposed to each
other; no adipose dorsal fin. In _Rondeletia_, the eyes are moderately
large, and ventral fins, with 5 rays, are present; in _Cetomimus_, the eyes
are very small, and ventral fins are absent.
{615}FAM. 9. CHIROTHRICIDAE.—Praemaxillaries delicate and styliform,
completely excluding the maxillaries from the upper border of the mouth;
jaws with feeble dentition or toothless; opercular apparatus complete.
Praecaudal vertebrae with robust parapophyses, to which ribs are attached.
Ventral fins far forwards.
These Fishes, of which three fossil genera are known from the Cretaceous of
Germany and Syria, appear to be related to the Scopelidae, from which the
strong parapophyses distinguish them. _Chirothrix_ is remarkable for its
excessively enlarged ventral fins with about 17 rays; these fins were taken
for the pectorals by the early describers. In _Telepholis_ and
_Exocoetoides_, the ventral fins are smaller than the pectorals, and formed
of 7 or 8 rays only; the dorsal region, in the former, is protected by a
covering of small, thin, rounded or polygonal dermal scutes, each bearing a
median tubercle.
[Illustration: FIG. 373.—_Chirothrix libanicus_, restored by A. S.
Woodward.]