Chapter XXI: The Fishes of the Deep Sea (7)

These fishes belong to the single family _Ophiocephalidæ_, Freshwater-fishes characteristic of the Indian region, which, however, have found their way into Africa, where they are represented by one or two species. Thirty-one species are known altogether, most of which are extremely abundant; some attain to a length of more than two feet. Like other tropical freshwater fishes, they are able to survive droughts, living in semi-fluid mud, or lying in a torpid state below the hard-baked crusts of the bottom of a tank from which every drop of water has disappeared. Respiration is probably entirely suspended during the state of torpidity, but whilst the mud is still soft enough to allow them to come to the surface, they rise at intervals to take in a quantity of air, by means of which their blood is oxygenised. This habit has been observed in some species to continue also to the period of the year in which the fish lives in normal water, and individuals which are kept in a basin and prevented from coming to the surface and renewing the air for respiratory purposes, are suffocated. The particular manner in which the accessory branchial cavity participates in respiratory functions is not known. It is a simple cavity, without an accessory branchial organ, the opening of which is partly closed by a fold of the mucous membrane.

SIXTEENTH DIVISION--ACANTHOPTERYGII LABYRINTHIBRANCHII.

_Body compressed, oblong or elevated, with scales of moderate size. A superbranchial organ in a cavity accessory to that of the gills._

FIRST FAMILY--LABYRINTHICI.

_Dorsal and anal spines present, but in variable numbers; ventrals thoracic. Lateral line absent, or more or less distinctly interrupted. Gill-opening rather narrow, the gill-membranes of both sides coalescent below the isthmus, and scaly; gills four; pseudobranchiæ rudimentary or absent._

Freshwater-fishes of the Cyprinoid division of the Equatorial zone. They possess the faculty of being able to live for some time out of the water, or in thick or hardened mud, in a still greater degree than the fishes of the preceding family. In the accessory branchial cavity there is lodged a laminated organ which evidently has the function of assisting in the oxygenisation of the blood. In _Anabas_ it is formed by several exceedingly thin bony laminæ, similar in form to the auricle, and concentrically situated one above the other, the innermost being the largest. The degree in which these laminæ are developed is dependent on age. In specimens from one inch and a half to two inches and a half long there are only two such laminæ, a third being indicated by a small protuberance at the central base of the second or outer laminæ. In specimens of from three to four inches in length the third lamina is developed, covering one-half of the second. The edges of all the laminæ are straight, not valanced. In specimens of from four to five inches a fourth lamina makes its appearance in the basal centre of the third lamina. The other laminæ continue to grow in their circumference, and their edges now become undulated and slightly frilled. Cuvier and Valenciennes have examined still larger specimens. The figure given by them and reproduced here was taken from a specimen six or seven inches long, and shows the superbranchial organ composed of six laminæ.

The air-bladder of the majority of these fishes is very large, extending far into the tail, and, therefore, divided behind by the hæmal spines into two lateral portions.

The Labyrinthici are generally of small size; they are capable of being domesticated, and some of them deserve particular attention on account of the dazzling beauty of their colours or the flavour of their flesh.

ANABAS.--Body compressed, oblong; præorbital and orbitals
serrated. Small teeth in the jaws and on the vomer; none on
the palatines. Dorsal and anal spines numerous. Lateral line
interrupted.

The “Climbing Perch” (_A. scandens_) is generally distributed over the Indian Region, and well known from its faculty of moving for some distance over land, and even up inclined surfaces. In 1797 Daldorf, in a memoir communicated to the Linnean Society of London, mentions that in 1791 he had himself taken an Anabas in the act of ascending a palm tree which grew near a pond. The fish had reached the height of five feet above the water, and was going still higher. In the effort to do this it held on to the bark of the tree by the preopercular spines, bent its tail, and stuck in the spines of the anal; then released its head, and, raising it, took a new hold with the preoperculum higher up. The fish is named in the Malayan language the “Tree Climber.” It rarely attains a length of seven inches.

_Spirobranchus_ from the Cape, and _Ctenopoma_ from Tropical Africa, represent _Anabas_ in that continent.

POLYACANTHUS.--Body compressed, oblong; operculum without spines
or serrature; cleft of the mouth small, more or less oblique,
not extending beyond the vertical from the orbit, and little
protractile. Small fixed teeth in the jaws, none on the palate.
Dorsal and anal spines numerous; the soft dorsal and anal,
the caudal, and the ventral, more or less elongate in mature
specimens. Caudal rounded. Lateral line interrupted or absent.

This genus is represented chiefly in the East Indian Archipelago; seven species are known; some of them have been domesticated on account of the beauty of their colours, and several varieties have been produced. One of them is to be mentioned, as, under the name of “Paradise-fish,” it has been introduced into the aquaria of Europe, where it readily breeds. It was known already to Lacépède, and has been mentioned since his time in all ichthyological works as _Macropus viridi-auratus_. In adult males some of the rays, and especially the caudal lobes, are much prolonged.

OSPHROMENUS.--Body compressed, more or less elevated; operculum
without spine or serrature. Small fixed teeth in the jaws, none
on the palate. Dorsal spines in small or moderate number; anal
spines in moderate or great number; ventral fins with the outer
ray very long, filiform. Lateral line not interrupted or absent.

To this genus belongs the celebrated “Gourami” (_Osphromenus olfax_), reputed to be one of the best flavoured Freshwater-fishes in the East-Indian Archipelago. Its original home is Java, Sumatra, Borneo, and several other islands; but thence it has been transported to, and acclimatised in, Penang, Malacca, Mauritius, and even Cayenne. Being an almost omnivorous fish and tenacious of life, it seems to recommend itself particularly for acclimatisation in other tropical countries, and specimens kept in captivity become as tame as carps. It attains the size of a large turbot. A second, but much smaller, species of this genus, _O. trichopterus_, is frequently kept in vessels on account of the exquisite beauty of its varying iridescent metallic tints; like other fishes of this family it is very pugnacious.

_Trichogaster_, a very common Bengalese fish, differs from _Osphromenus_ in having the ventral fins reduced to a single long filament.

BETTA.--Body compressed, oblong; operculum without spine or
serrature. Small fixed teeth in the jaws, none on the palate.
Dorsal fin short, on the middle of the back, without any pungent
spine; anal fin long. Ventral fin with five soft rays, the outer
one being produced. Lateral line interrupted or absent.

A species of this genus (_B. pugnax_) is, on account of its pugnacious habits, reared by the Siamese. Cantor gives the following account:--“When the fish is in a state of quiet, its dull colours present nothing remarkable; but if two be brought together, or if one sees its own image in a looking-glass, the little creature becomes suddenly excited, the raised fins and the whole body shine with metallic colours of dazzling beauty, while the projected gill membrane, waving like a black frill round the throat, adds something of grotesqueness to the general appearance. In this state it makes repeated darts at its real or reflected antagonist. But both, when taken out of each other’s sight, instantly become quiet. This description was drawn up in 1840, at Singapore, by a gentleman who had been presented with several by the King of Siam. They were kept in glasses of water, fed with larvæ of mosquitoes, and had thus lived for many months. The Siamese are as infatuated with the combats of these fish as the Malays are with their cock-fights; and stake on the issue considerable sums, and sometimes their own persons and families. The license to exhibit fish-fights is farmed, and brings a considerable annual revenue to the King of Siam. The species abounds in the rivulets at the foot of the hills of Penang. The inhabitants name it ‘Pla-kat,’ or the ‘Fighting-fish;’ but the kind kept especially for fighting is an artificial variety cultivated for the purpose.”

MICRACANTHUS.--This genus represents the three last-named genera in Africa, where it has been recently discovered in tributaries of the river Ogooué. It seems to differ from the Indian genera chiefly by its more elongate body, the structure of the fins being scarcely different (D. 3/7, A. 4/23, V. 1/4).

SECOND FAMILY--LUCIOCEPHALIDÆ.

_Body elongate, covered with scales of moderate size. Lateral line present. Teeth small. Gill-opening wide; pseudobranchiæ none. The superbranchial organ is formed by two branchial arches, which are dilated into a membrane. One short dorsal fin; dorsal and anal spines none; ventrals composed of one spine and five rays. Air-bladder none._

A small Freshwater-fish (_Luciocephalus pulcher_), from the East-Indian Archipelago.

SEVENTEENTH DIVISION--ACANTHOPTERYGII LOPHOTIFORMES.

_Body riband shaped, with the vent near its extremity; a short anal behind the vent; dorsal fin as long as the body._

Only one species is known of this division or family, _Lophotes cepedianus_. It is most probably a deep-sea fish, but does not descend to so great a depth as the _Trachypteridæ_, its bony and soft parts being well coherent. It is a scarce fish, hitherto found in the Mediterranean, off Madeira, and in the Sea of Japan; its length is known to exceed five feet. The head is elevated into a very high crest, and the dorsal fin commences with an exceedingly strong and long spine on the head. Silvery, with rose-coloured fins.

EIGHTEENTH DIVISION--ACANTHOPTERYGII TÆNIIFORMES.

_Body riband shaped; dorsal fin as long as the body; anal absent; caudal rudimentary, or not in the longitudinal axis of the fish._

The “Ribbon-fishes” are true deep-sea fishes, met with in all parts of the oceans, generally found when floating dead on the surface, or thrown ashore by the waves. Their body is like a band, specimens of from fifteen to twenty feet long being from ten to twelve inches deep, and about an inch or two broad at their thickest part. The eye is large and lateral; the mouth small, armed with very feeble teeth; the head deep and short. A high dorsal fin runs along the whole length of the back, and is supported by extremely numerous rays; its foremost portion, on the head, is detached from the rest of the fin, and composed of very elongate flexible spines. The anal fin is absent. The caudal fin (if preserved, which is rarely the case, in adult specimens) has an extra-axial position, being directed upwards like a fan. The ventrals are thoracic, either composed of several rays or reduced to a single long filament. The coloration is generally silvery, with rosy fins.

When these fishes reach the surface of the water the expansion of the gases within their body has so loosened all parts of their muscular and bony system, that they can be lifted out of the water with difficulty only, and nearly always portions of the body and fins are broken and lost. The bones contain very little bony matter, are very porous, thin and light. At what depths Ribbon-fishes live is not known; probably the depths vary for different species; but although none have been yet obtained by means of the deep-sea dredge, they must be abundant at the bottom of all oceans, as dead fishes or fragments of them are frequently obtained. Some writers have supposed from the great length and narrow shape of these fishes that they have been mistaken for “Sea-serpents;” but as these monsters of the sea are always represented by those who have had the good fortune of meeting with them as remarkably active, it is not likely that harmless Ribbon-fishes, which are either dying or dead, have been the objects described as “Sea-serpents.”

Young Ribbon-fishes (from two to four inches) are not rarely met with near the surface; they possess the most extraordinary development of fin rays observed in the whole class of fishes, some of them being several times longer than the body, and provided with lappet-like dilatations. There is no doubt that fishes with such delicate appendages are bred and live in depths where the water is absolutely quiet, as a sojourn in the disturbed water of the surface would deprive them at once of organs which must be of some utility for their preservation.

Ribbon-fishes are divided into three genera:--

TRACHYPTERUS.--In which the ventral rays are well developed, and composed of several more or less branched rays. Specimens of this genus have been taken in the Mediterranean, Atlantic, at Mauritius, and in the Eastern Pacific. The “Deal-fish” (_T. arcticus_) is often met with in the North Atlantic, and specimens are generally found after the equinoctial gales on the coasts of the Orkneys and North Britain.

STYLOPHORUS.--Without ventrals, and with the tail terminating in an exceedingly long cord-like appendage. Known from one specimen only, found at the beginning of this century between Cuba and Martinique. It is eleven inches long, and preserved in the Museum of the Royal College of Surgeons in London.

_Regalecus._--Each ventral fin is reduced to a long filament, dilated at the extremity; caudal fin rudimentary or absent. These are the largest of all Ribbon-fishes, specimens being on record the length of which exceeded twenty feet. They have been taken in the Mediterranean, North and South Atlantic, Indian Ocean, and on the coast of New Zealand. They are frequently called “Kings of the herrings,” from the erroneous notion that they accompany the shoals of herrings; or “Oar-fishes,” from their two ventral fins, which have a dilatation at their extremity not unlike the blade of an oar. One or more species (_R. banksii_) are sometimes found on the British coasts, but they are very scarce, not more than sixteen captures having been recorded between the years 1759 and 1878.

NINETEENTH DIVISION--ACANTHOPTERYGII NOTACANTHIFORMES.

_Dorsal fin short, composed of short, isolated spines, without a soft portion. Anal fin very long, anteriorly with many spines; ventrals abdominal, with more than five soft and several unarticulated rays._

_Notacanthus_ is the most aberrant type of Acanthopterygians. Of the characteristics of this order the development of spines in the vertical fins is the only one preserved in the fishes of this genus. Their body is elongate, covered with very small scales; the snout protrudes beyond the mouth. Eyes lateral, of moderate size; dentition feeble. Five species are known from the Arctic Ocean, Mediterranean, Atlantic, and Southern Pacific. They inhabit considerable depths, probably from 100 to 400 fathoms, and during the “Challenger” expedition specimens have been obtained from an alleged depth of 1875 fathoms.

SECOND ORDER:

ACANTHOPTERYGII PHARYNGOGNATHI.

_Part of the rays of the dorsal, anal, and ventral fins are non-articulated spines. The lower pharyngeals coalesced. Air-bladder without pneumatic duct._

FIRST FAMILY--POMACENTRIDÆ.

_Body short, compressed, covered with ctenoid scales. Dentition feeble; palate smooth. The lateral line does not extend to the caudal fin, or is interrupted. One dorsal fin, with the spinous portion as well developed as the soft, or more. Two, sometimes three, anal spines; the soft anal similar to the soft dorsal. Ventral fins thoracic, with one spine and five soft rays. Gills three and a half; pseudobranchiæ and air-bladder present. Vertebræ, twelve abdominal and fourteen caudal._

The fishes of this family are marine; they resemble the Chætodonts with regard to their mode of life, living chiefly in the neighbourhood of coral formations. Like them they are beautifully coloured, the same patterns being sometimes reproduced in members of both families, proving that the development and distribution of colours is due to the agencies of climate, of the surroundings and of the habits of animals. The geographical range of the _Pomacentridæ_ is co-extensive with that of the Chætodonts, the species being most numerous in the Indo-Pacific and Tropical Atlantic, a few extending northwards to the Mediterranean and Japan, southwards to the coasts of South Australia. They feed chiefly on small marine animals, and such as have compressed teeth appear to feed on the small Zoophytes covering the banks, round which these “Coral-fishes” abound. In a fossil state this family is known from a single genus only, _Odonteus_, from Monte Bolca, allied to _Heliastes_. The recent genera belonging to this family are:--_Amphiprion_, _Premnas_, _Dascyllus_, _Lepidozygus_, _Pomacentrus_, _Glyphidodon_, _Parma_, and _Heliastes_. About 120 species are known.

SECOND FAMILY--LABRIDÆ.

_Body oblong or elongate, covered with cycloid scales. The lateral line extends to the caudal, or is interrupted. One dorsal fin, with the spinous portion as well developed as, or more than, the soft. The soft anal similar to the soft dorsal. Ventral fins thoracic, with one spine and five soft rays. Palate without teeth. Branchiostegals five or six; gills three and a half; pseudobranchiæ and air-bladder present. Pyloric appendages none; stomach without cæcal sac._

The “Wrasses” are a large family of littoral fishes, very abundant in the temperate and tropical zones, but becoming scarcer towards the Arctic and Antarctic circles, where they disappear entirely. Many of them are readily recognised by their thick lips, which are sometimes internally folded, a peculiarity which has given to them the German term of “Lip-fishes.” They feed chiefly on mollusks and crustaceans, their dentition being admirably adapted for crushing hard substances. Many species have a strong curved tooth at the posterior extremity of the intermaxillary, for the purpose of pressing a shell against the lateral and front teeth by which it is crushed. Other Wrasses feed on corals, others on zoophytes; a few are herbivorous. In all Wrasses the upper pharyngeal bones seem to be jointed to the basi-occipital; but whilst in _Labrus_ the basi-occipital is raised on each side into a large flattish condyle, fitting into a concavity of the upper pharyngeals, in _Scarus_ the mode of articulation is reversed, the basi-occipital having a pair of long grooves, in which the oblong condyles of the upper pharyngeals slide forwards and backwards. Beautiful colours prevail in this family, permanent pigmentary colours as well as passing iridescent reflections of the scales. Some species remain very small, others grow to a weight of fifty pounds. The larger kinds especially are prized as food, the smaller less so.

Remains of Labridæ, recognised by their united pharyngeals, which bear molar-like teeth, are not scarce in tertiary formations of France, Germany, Italy, and England. Such remains from Monte Bolca and the Swiss Molasse have been referred to the genus _Labrus_. Others, _Nummopalatus_ and _Phyllodus_, are allied, but cannot be assigned, to one of the recent genera; the latter genus is first represented in cretaceous formations of Germany. Another genus, _Taurinichthys_, from the Miocene of France, represents the _Odacina_ of the living fauna. _Egertonia_, from the Isle of Sheppey, differs so much from all recent Labroid genera that its pertinence to this family appears doubtful.

[See _J. Cocchi_, Monografia dei Pharyngodopilidæ, 1866; and _E.
Sauvage_, Sur le genre Nummopalatus, in Bull. Soc. Geol. France,
1875.]

LABRUS.--Body compressed, oblong, covered with scales of
moderate size, in more than forty transverse series; snout more
or less pointed; imbricate scales on the cheeks and opercles;
none or only a few on the interoperculum. Teeth in the jaws
conical, in a single series. Dorsal spines numerous, thirteen
or twenty-one, none of which are prolonged; anal spines three.
Lateral line not interrupted.

Young “Wrasses” differ from mature specimens in having the præoperculum serrated. The headquarters of this genus are the Mediterranean, whence it ranges, gradually diminishing towards the north, along all the shores of Europe. Nine species are known; British are the “Ballan Wrasse” (_L. maculatus_), and the “Striped or Red Wrasse” or “Cook” (_L. mixtus_). The two sexes of the latter species are very differently coloured; the male being generally ornamented with blue streaks, or a blackish band along the body, whilst the female has two or three large black blotches across the back of the tail.

CRENILABRUS are Labrus with serrated præoperculum; the number of
their dorsal spines varies from thirteen to eighteen, and the
scales are arranged in less than forty transverse series.

The range of this genus is co-extensive with _Labrus_. _C. melops_, the “Gold-sinny,” or “Cork-wing,” is common on the British coasts.

TAUTOGA.--Body compressed, oblong, covered with small scales;
scales on the cheek rudimentary, opercles naked. Teeth in the
jaws conical, in double series; no posterior canine tooth.
Dorsal spines seventeen, anal spines three. Lateral line not
interrupted.

The “Tautog,” or “Black-fish,” is common on the Atlantic coasts of temperate North America, and much esteemed as food.

CTENOLABRUS.--Body oblong, covered with scales of moderate size;
imbricate scales on the cheeks and opercles. Teeth in the jaws
in a band, with an outer series of stronger conical teeth; no
posterior canine tooth. Dorsal spines from sixteen to eighteen;
anal spines three. Lateral line not interrupted.

Four species, from the Mediterranean and the temperate parts of the North Atlantic, _Ct. rupestris_ being common on the British, and _Ct. burgall_ on the North American coasts.

ACANTHOLABRUS.--A Wrasse with five or six anal spines, and with
the teeth in a band.

From the Mediterranean and British coasts (_A. palloni_).

CENTROLABRUS.--Wrasses with four or five anal spines, and with
the teeth in a single series.

Two species are known from Madeira and the Canary Islands, and one from northern Europe and Greenland. The latter is scarce on the British coasts, but bears a distinct name on the south coast, where it is called “Rock-cook.”

LACHNOLAEMUS from the West Indies, and MALACOPTERUS from Juan Fernandez, are Labroids, closely allied to the preceding North Atlantic genera.

COSSYPHUS.--Body compressed, oblong, with scales of moderate
size; snout more or less pointed; imbricate scales on the cheeks
and opercles; basal portion of the vertical fins scaly. Lateral
line not interrupted. Teeth in the jaws in a single series; four
canine teeth in each jaw anteriorly; a posterior canine tooth.
Formula of the fins: D. 12/9–11, A. 3/12.

Twenty species are known from the tropical zone and coasts adjoining it; some, like _G. gouldii_ from Tasmania, attain a length of three or four feet.

CHILINUS.--Body compressed, oblong, covered with large scales;
lateral line interrupted; cheeks with two series of scales;
præoperculum entire; teeth in a single series, two canines in
each jaw; no posterior canine tooth; lower jaw not produced
backwards. Dorsal spines subequal in length; formula of the
fins: D. 9–10/10–9, A. 3/8.

Common in the tropical Indo-Pacific, whence more than twenty species are known. Hybrids between the different species of this genus are not uncommon.

EPIBULUS.--Closely allied to the preceding genus, but with
a very protractile mouth, the ascending branches of the
intermaxillaries, the mandibles, and the tympanic being much
prolonged.

This fish (_E. insidiator_) is said to seize marine animals by suddenly thrusting out its mouth and engulphing those that come within the reach of the elongated tube. It attains a length of twelve inches, is common in the tropical Indo-Pacific, and varies much in coloration.

ANAMPSES.--Distinguished by its singular dentition, the
two front teeth of each jaw being prominent, directed forwards,
compressed, with cutting edge. D. 9/12, A. 3/12.

Beautifully coloured fishes from the tropical Indo-Pacific. Ten species.

PLATYGLOSSUS.--Scales in thirty or less transverse series;
lateral line not interrupted. A posterior canine tooth. Dorsal
spines nine.

Small beautifully coloured Coral-fishes, abundant in the equatorial zone and the coasts adjoining it. Some eighty species are known (inclusive of the allied genera _Stethojulis_, _Leptojulis_, and _Pseudojulis_).

NOVACULA.--Body strongly compressed, oblong, covered with
scales of moderate size; head compressed, elevated, obtuse,
with the supero-anterior profile more or less parabolic; head
nearly entirely naked. Lateral line interrupted. No posterior
canine tooth. D. 9/12, A. 3/12; the two anterior dorsal spines
sometimes remote or separate from the others.

Twenty-six species are known from the tropical zone, and the warmer parts of the temperate zones. They are readily recognised by their compressed, knife-shaped body, and peculiar physiognomy; they scarcely exceed a length of twelve inches.

JULIS.--Scales of moderate size; lateral line not interrupted.
Head entirely naked. Snout of moderate extent, not produced; no
posterior canine tooth. Dorsal spines ten.

Co-extensive with _Platyglossus_ in their geographical distribution, and of like beautiful coloration and similar habits. Some of the most common fishes of the Indo-Pacific, as _J. lunaris_, _trilobata_, and _dorsalis_, belong to this genus.

CORIS.--Scales small, in fifty or more transverse series;
lateral line not interrupted. Head entirely naked. Dorsal spines
nine.

Twenty-three species, distributed like _Platyglossus_; two reach the south coast of England, _Coris julis_ and _C. giofredi_, said to be male and female of the same species. Some belong to the most gorgeously coloured kinds of the whole class of fishes.

Genera allied to the preceding Labroids are--_Choerops_, _Xiphochilus_, _Semicossyphus_, _Trochocopus_, _Decodon_, _Pteragogus_, _Clepticus_, _Labrichthys_, _Labroides_, _Duymæria_, _Cirrhilabrus_, _Doratonotus_, _Pseudochilinus_, _Hemigymnus_, _Gomphosus_, _Cheilio_, and _Cymolutes_.

PSEUDODAX.--Scales of moderate size; lateral line continuous;
cheeks and opercles scaly. Each jaw armed with two pairs of
broad incisors, and with a cutting lateral edge; teeth of the
lower pharyngeal confluent, pavement-like. Dorsal spines eleven.

One species (_P. moluccensis_) from the East Indian Archipelago.

SCARUS.--Jaws forming a sharp beak, the teeth being soldered
together. The lower jaw projecting beyond the upper. A single
series of scales on the cheek; dorsal spines stiff, pungent; the
upper lip double in its whole circuit. The dentigerous plate of
the lower pharyngeal is broader than long.

The fishes of this genus, and the three succeeding, are known by the name of “Parrot-wrasses.” Of _Scarus_ one species (_S. cretensis_) occurs in the Mediterranean, and nine others in the tropical Atlantic. The first was held in high repute by the ancients, and Aristotle has several passages respecting its rumination. It was most plentiful and of the best quality in the Carpathian Sea, between Crete and Asia Minor, but was not unknown even in early times on the Italian coasts, though Columella says that it seldom passed beyond Sicily in his day. But in the reign of Claudius, according to Pliny, Optatus Elipentius brought it from the Troad, and introduced it into the sea between Ostium and Campagna. For five years all that were caught in the nets were thrown into the sea again, and from that time it was an abundant fish in that locality. In the time of Pliny it was considered to be the first of fishes _(Nunc Scaro datur principatus_); and the expense incurred by Elipentius was justified, in the opinion of the Roman gourmands, by the extreme delicacy of the fish. It was a fish, said the poets, whose very excrements the gods themselves were unwilling to reject. Its flesh was tender, agreeable, sweet, easy of digestion, and quickly assimilated; yet if it happened to have eaten an Aplysia, it produced violent diarrhœa. In short, there is no fish of which so much has been said by ancient writers. In the present day the Scarus of the Archipelago is considered to be a fish of exquisite flavour; and the Greeks still name it _Scaro_, and eat it with a sauce made of its liver and intestines. It feeds on fucus; and Valenciennes thinks that the necessity for masticating its vegetable diet thoroughly, and the working of it with that intent backwards and forwards in the mouth, may have given rise to the notion of its being a ruminant; and it is certain that its aliment is very finely divided when it reaches the stomach.

SCARICHTHYS.--Differing from _Scarus_ only in having flexible
dorsal spines.

Two species from the Indo-Pacific.

CALLYODON.--Differing from _Scarichthys_ in having the upper lip
double posteriorly only.

Nine species from the tropical zone.

PSEUDOSCARUS.--Jaws forming a strong beak, the teeth being
soldered together. The upper jaw projecting beyond the lower.
Two or more series of scales on the cheek. The dentigerous plate
of the lower pharyngeal longer than broad.

This tropical genus contains by far the greatest number of Scaroid Wrasses, some seventy species being known, and a still greater number of names being introduced into the various Ichthyological works. They are beautifully coloured, but the colours change with age, and vary in an extraordinary degree in the same species. They rapidly fade after death, so that it is almost impossible to recognise in preserved specimens the species described from living individuals. Many attain to a rather large size, upwards of three feet in length. The majority are eaten, but some acquire poisonous properties from their food, which consists either of corals or of fucus.

ODAX.--The edge of each jaw is sharp, without distinct teeth.
The dentigerous plate of the lower pharyngeal triangular, much
broader than long. Cheeks and opercles scaly; scales of the body
small or rather small; lateral line continuous. Snout conical.
Dorsal spines rather numerous, flexible.

Six species from the coasts of Australia and New Zealand. Small. The species figured (_O. radiatus_) is from Western Australia.

CORIDODAX.--Jaws as in _Odax_, head naked. Scales of the body
small; lateral line continuous. Snout of moderate extent. Dorsal
spines numerous, flexible.

The “Butter-fish,” or “Kelp-fish” of the colonists of New Zealand (_C. pullus_), is prized as food, and attains to a weight of four or five pounds. It feeds on zoophytes, scraping them from the surface of the kelp, with its curiously formed teeth. Its bones are green, like those of _Belone_.

OLISTHEROPS, from King George’s Sound, has scales of moderate size, but agrees otherwise with _Coridodax_.

SIPHONOGNATHUS.--Head and body very elongate, snout long, as in
_Fistularia_; upper jaw terminating in a long, pointed, skinny
appendage; opercles and cheeks scaly; scales of moderate size;
lateral line continuous. Dorsal spines numerous, flexible. Jaws
as in _Odax_; the dentigerous plate of the lower pharyngeal very
narrow.

_S. argyrophanes_, from King George’s Sound, is the most aberrant type of Wrasses, whose principal characters are retained, but united with a form of the body which resembles that of a Pipe-fish.

THIRD FAMILY--EMBIOTOCIDÆ.

_Body compressed, elevated or oblong, covered with cycloid scales; lateral line continuous. One dorsal fin, with a spinous portion, and with a scaly sheath along the base, which is separated by a groove from the other scales; anal with three spines and numerous rays; ventral fins thoracic, with one spine and five rays. Small teeth in the jaws, none on the palate. Pseudobranchiæ present. Stomach siphonal, pyloric appendages none. Viviparous._

Marine Fishes characteristic of the fauna of the temperate North Pacific, the majority living on the American side, and only a few on the Asiatic. All are viviparous (see Fig. 70, p. 159). Agassiz describes the development of the embryoes as a normal ovarian gestation, the sac containing the young not being the oviduct but the ovarian sheath, which fulfils the functions of the ovary. This organ presents two modes of arrangement: in one there is a series of triangular membranous flaps communicating with each other, between which the young are arranged, mostly longitudinally, the head of one to the tail of another, but sometimes with the bodies curved, to the number of eighteen or twenty; in the other, the cavity is divided by three membranes converging to a point, into four compartments, not communicating with each other except towards the genital opening, the young being arranged in the same longitudinal manner. The proportionate size of the young is very remarkable. In a female specimen 10½ inches long, and 4½ inches high, the young were nearly 3 inches long and 1 inch high. Seventeen species are known, the majority of which belong to _Ditrema_, and one to _Hysterocarpus_. They do not attain to a large size, varying from three-quarters to three pounds in weight.

FOURTH FAMILY--CHROMIDES.

_Body elevated, oblong or elongate, scaly, the scales being generally ctenoid. Lateral line interrupted or nearly so. One dorsal fin, with a spinous portion; three or more anal spines; the soft anal similar to the soft dorsal. Ventral fins thoracic, with one spine and five rays. Teeth in the jaws small, palate smooth. Pseudobranchiæ none. Stomach coecal; pyloric appendages none._

Freshwater-fishes of rather small size from the tropical parts of Africa and America; one genus from Western India. The species with lobate teeth, and with many circumvolutions of the intestines, are herbivorous, the other carnivorous.

ETROPLUS.--Body compressed, elevated, covered with ctenoid
scales of moderate size. Lateral line indistinct. Dorsal and
anal spines numerous. Teeth compressed, lobate, in one or
two series. Anterior prominences of the branchial arches not
numerous, short, conical, hard. Dorsal fin not scaly.

Two species from Ceylon and Southern India.

CHROMIS.--Body compressed, oblong, covered with cycloid
scales of moderate size. Dorsal spines numerous, anal spines
three. Teeth compressed, more or less lobate, in one series.
Anterior prominences of the branchial arches short, thin,
lamelliform, non-serrated. Dorsal fin not scaly.

Some twenty species are known from the fresh waters of Africa and Palestine; the most celebrated is the “Bulti,” or “Bolty,” of the Nile, one of the few well-flavoured fishes of that river; it grows to the length of twenty inches. Two or three species of this genus occur in the Jordan and Lake of Galilee.

HEMICHROMIS, differing from _Chromis_ in having conical teeth in
one or two series.

Ten species, the range of which is co-extensive with that of _Chromis_. One species, _H. sacra_, is abundant in the Lake of Galilee.

PARETROPLUS, differing from _Hemichromis_ in having nine anal
spines.

One species from Madagascar.

ACARA.--Body compressed, oblong, covered with ctenoid scales
of moderate size. Dorsal spines numerous, anal spines three or
four; base of the soft dorsal nearly uncovered by scales. Teeth
in a band, small, conical. Anterior prominences of the first
branchial arch very short tubercles.

Some twenty species are known from the fresh waters of Tropical America, _A. bimaculata_ being one of the most common fishes of that region. All are very small.

HEROS.--Differing from _Acara_ in having more than four anal
spines.

Some fifty species are known from the fresh waters of Tropical America, especially Central America, where almost every large lake or river is tenanted by one or more peculiar species. They are of rather small size, rarely exceeding a length of twelve inches.

Genera allied to _Heros_, and likewise from Tropical America, are _Neetroplus_, _Mesonauta_, _Petenia_, _Uaru_, and _Hygrogonus_.

CICHLA.--Form of the body perch-like. Scales small; the spinous
and soft portions of the dorsal fin of nearly equal extent,
and separated by a notch; anal spines three. Each jaw with a
broad band of villiform teeth. The outer branchial arch with
lanceolate crenulated prominences along its concave side. Dorsal
and anal fins scaly.

Four species from Brazil, Guyana, and Peru.

CRENICICHLA.--Body low, sub-cylindrical; scales small or rather
small. The spinous portion of the dorsal is much more developed
than the soft, both being continuous, and not separated by a
notch; anal spines three. Præopercular margin serrated. Each
jaw with a band of conical teeth. The outer branchial arch with
short tubercles. Dorsal and anal fins naked.

Ten species from Brazil and Guyana.

The following genera complete the list of South American Chromides: _Chætobranchus_, _Mesops_, _Satanoperca_, _Geophagus_, _Symphysodon_, and _Pterophyllum_.

THIRD ORDER--ANACANTHINI.

_Vertical and ventral fins without spinous rays. The ventral fins, if present, are jugular or thoracic. Air-bladder, if present, without pneumatic duct._

These characters are common to all the members of this order, with the exception of a freshwater-fish from Tasmania and South Australia (_Gadopsis_), which has the anterior portion of the dorsal and anal fins formed of spines.

FIRST DIVISION--ANACANTHINI GADOIDEI.

_Head and body symmetrically formed._

FIRST FAMILY--LYCODIDÆ.

_Vertical fins confluent. Ventral fin, if present, small, attached to the humeral arch, jugular. Gill-opening narrow, the gill-membrane being attached to the isthmus._

Marine littoral fishes of small size, resembling Blennies, chiefly represented in high latitudes, but a few living within the tropical zone.

LYCODES.--Body elongate, covered with minute scales imbedded in
the skin, or naked; lateral line more or less indistinct. Eye
of moderate size. Ventral small, short, rudimentary, jugular,
composed of several rays. Upper jaw overlapping the lower.
Conical teeth in the jaws, on the vomer, and on the palatine
bones. Barbel none. Five or six branchiostegals; gill-opening
narrow, the gill-membranes being attached to the isthmus.
Pseudobranchiæ present. Air-bladder none. Pyloric appendages
two, or rudimentary, or entirely absent. No prominent anal
papilla.

Nine species are known from the Arctic Ocean, four from the southern extremity of the American continent.

GYMNELIS.--Body elongate, naked. Eye of moderate size or rather
small. Ventrals none. Vent situated at some distance backwards
from the head. Small conical teeth in the jaws, on the vomer
and palatine bones. Jaws equal anteriorly. Barbel none. Six
branchiostegals; gill-opening narrow, the gill membranes being
attached to the isthmus. Pseudobranchiæ present; air-bladder
none. Pyloric appendages two; no prominent anal papilla.

One species (_G. viridis_) from Greenland, the other (_G. pictus_) from the Straits of Magelhæn.

The other genera belonging to this family are _Uronectes_ from Baffin’s Bay, _Microdesmus_ from Panama, _Blennodesmus_ from the coast of North-Eastern Australia, and _Maynea_ from the Straits of Magelhæn.

SECOND FAMILY--GADIDÆ.

_Body more or less elongate, covered with small smooth scales. One, two, or three dorsal fins, occupying nearly the whole of the back; rays of the posterior dorsal well developed; one or two anal fins. Caudal free from dorsal and anal, or, if they are united, the dorsal with a separate anterior portion. Ventrals jugular, composed of several rays, or, if they are reduced to a filament, the dorsal is divided into two. Gill-opening wide; the gill-membranes generally not attached to the isthmus. Pseudobranchiæ none, or glandular, rudimentary. An air-bladder and pyloric appendages generally present._

The family of “Cod-fishes” consists partly of littoral and surface species (and they form the majority), partly of deep-sea forms. The former are almost entirely confined to the temperate zones, extending beyond the Arctic Circle; the latter have, as deep-sea fishes generally, a much wider range, and hitherto have been found chiefly at considerable depths of rather low latitudes. Only two or three species inhabit fresh waters. They form one of the most important articles of food and subsistence to the fishermen in Europe and North America, and to whole tribes bordering upon the Arctic Ocean.

Fossil remains are scarce. _Nemopteryx_ and _Palæogadus_ have been described from the schists of Glaris, a formation believed to have been the bottom of a very deep sea. In the clay of Sheppey species occur allied to _Gadus_, _Merluccius_, and _Phycis_; others, not readily determinable, have been found at Licata in Sicily (Miocene).

GADUS.--Body moderately elongate, covered with small scales.
A separate caudal, three dorsal, and two anal fins; ventrals
narrow, composed of six or more rays. Teeth in the upper jaw in
a narrow band; vomerine teeth; none on the palatines.

Arctic and temperate zones of the Northern Hemisphere. Eighteen species are known, of which the following are the most important:--

_Gadus morrhua_, the common “Cod-fish”--in German called “Kabeljau” when fresh and old, “Dorsch” when young and fresh, “Stock-fish” when dried, “Labberdan” when salted--measures from two to four feet, and attains to a weight of one hundred pounds. On the British coasts and in the German Ocean it is generally of a greenish or brownish-olive colour, with numerous yellowish or brown spots. Farther northwards darker-coloured specimens, frequently without any spots, predominate; and on the Greenland, Iceland, and North Scandinavian coasts the Cod have often a large irregular black blotch on the side. The Cod-fish occurs between 50° and 75° lat. N., in great profusion, to a depth of 120 fathoms, but is not found nearer the Equator than 40° lat. Close to the coast it is met with singly all the year round, but towards the spawning-time it approaches the shore in numbers, which happens in January in England and not before May on the American coasts. The English resorted to the cod-fisheries of Iceland before the year 1415, but since the sixteenth century most vessels go to the banks of Newfoundland, and almost all the preserved Cod consumed during Lent in the various continental countries is imported from across the Atlantic. At one time the Newfoundland cod-fishery rivalled in importance the whale-fishery and the fur trade of North America. Cod-liver oil is prepared from the liver on the Norwegian coast, but also other species of this genus contribute to this most important drug.

_Gadus tomcodus_ abundantly occurs on the American coasts; it remains within smaller dimensions than the common Cod-fish. _Gadus æglefinus_, the “Haddock” (“Schell-fisch” of the Germans, “Hadot” of the French), is distinguished by a black lateral line and a blackish spot above the pectoral fin. It attains to a length of three feet in the higher latitudes, but remains smaller on more southern coasts; like the Cod it extends across the Atlantic. The largest specimens are taken on the British coast in winter, because at that time they leave the deep water to spawn on the coast. _Gadus merlangus_, the “Whiting,” with a black spot in the axil of the pectoral fin. _Gadus luscus_, the “Bib,” “Pout,” or “Whiting-pout,” with cross-bands during life, and with a black axillary spot, rarely exceeding a weight of five pounds. _Gadus fabricii_, a small species, but occurring in incredible numbers on the shores near the Arctic circle, and ranging to 80° lat. N. _Gadus pollachius_, the “Pollack,” without a barbel at the chin, and with the lower jaw projecting beyond the upper. _Gadus virens_, the “Coal-fish,” valuable on account of its size and abundance, and therefore preserved for export like the Cod.

The fishes of the genus _Gadus_ are bathymetrically succeeded by several genera, as _Gadiculus_, _Mora_, and _Strinsia_; however these do not descend to sufficiently great depths to be included into the deep-sea Fauna; the two following are true deep-sea fishes.

HALARGYREUS.--Body elongate, covered with small scales. Two
dorsal and two anal fins; ventrals composed of several rays.
Jaws with a band of minute villiform teeth; vomer and palatines
toothless. No barbel.

The single species known, _H. johnsonii_, proves to be a deep-sea fish by its organisation as well as geographical distribution. Originally known from a single specimen, which was obtained at Madeira, it has since been found off the coast of New Zealand. There is no doubt that it will be discovered also in intermediate seas.

MELANONUS.--Head and body rather compressed, covered with
cycloid scales of moderate size, and terminating in a long
tapering tail, without caudal. Eye of moderate size. Villiform
teeth in the jaws, on the vomer and palatine bones. Barbel
none. A short anterior dorsal, the second extending to the end
of the tail, and the anal being of similar length. Ventrals
composed of several rays. Bones soft and flexible.

This is one of the discoveries made during the expedition of the “Challenger.” The single specimen obtained is of a deep-black colour, and was dredged up at a depth of 1975 fathoms in the Antarctic Ocean.

MERLUCCIUS.--Body elongate, covered with very small scales. A
separate caudal; two dorsal fins and one anal; ventrals well
developed, composed of seven rays. Teeth in the jaws and on the
vomer rather strong, in double or triple series. No barbel.

Two species are known of this genus, widely separated in their distribution. The European species, _M. vulgaris_, the “Hake,” is found on both sides of the Atlantic, and grows to a length of four feet. It is caught in great numbers, and preserved as “Stock-fish.” The second species _M. gayi_, is common in the Straits of Magelhæn and on the coast of Chili, less so in New Zealand.

The vertebral column of this genus shows a singular modification of the apophyses. The neural spines of all the abdominal vertebræ are extremely strong, dilated, wedged into one another. The parapophyses of the third to sixth vertebræ are slender, styliform, whilst those of all the following abdominal vertebræ are very long and broad, convex on the upper and concave on the lower surface; the two or three anterior pairs are, as it were, inflated. The whole forms a strong roof for the air-bladder, reminding us of a similar structure in _Kurtus_.

PSEUDOPHYCIS.--Body of moderate length, covered with rather
small scales. A separate caudal, two dorsals, and one anal;
ventral fins very narrow and styliform, but composed of several
rays. Jaws with a band of small teeth; vomer and palatines
toothless. Chin with a barbel.

Two species, of which _Ps. bachus_ is common on the coast of New Zealand.

Allied genera are _Lotella_, _Physiculus_, _Uraleptus_, and _Læmonema_, from moderate depths, obtained chiefly off Madeira and the Southern Temperate Zone.

PHYCIS.--Body of moderate length, covered with small scales.
Fins more or less enveloped in loose skin. A separate caudal;
two dorsal fins and one anal; the anterior dorsal composed of
from eight to ten rays; ventrals reduced to a single long ray,
bifid at its end. Small teeth in the jaws and on the vomer;
palatine bones toothless. Chin with a barbel.

Six species from the temperate parts of the North Atlantic and the Mediterranean, one, _Ph. blennioides_, is occasionally found on the British coast.

HALOPORPHYRUS.--Body elongate, covered with small scales. A
separate caudal, two dorsal fins, and one anal; the first dorsal
with four rays; ventrals narrow, composed of six rays. Jaws and
vomer with villiform teeth; palatine bones toothless. Chin with
a barbel.

A small genus of deep-sea fishes, of which three species are known. They offer a striking instance of the extraordinary distribution of deep-sea fishes; _H. lepidion_ occurs in from 100 to 600 fathoms in the Mediterranean and the neighbouring parts of the Atlantic, off the coast of Japan, and various parts of the South Atlantic; _H. australis_ in from 55 to 70 fathoms in the Straits of Magelhæn; and finally _H. rostratus_ in from 600 to 1375 fathoms, midway between the Cape of Good Hope and Kerguelen’s Land, and in the South Atlantic.

LOTA.--Body elongate, covered with very small scales. A separate
caudal, two dorsal fins, and one anal; ventrals narrow, composed
of six rays. Villiform teeth in the jaws and on the vomer; none
on the palatines. The first dorsal with from ten to thirteen
well-developed rays. Chin with a barbel.

The “Burbot,” or “Eel-pout” (_L. vulgaris_, Fig. 8, p. 43), is a Freshwater-fish which never enters salt water. It is locally distributed in Central and Northern Europe and North America; it is one of the best Freshwater-fishes, and exceeds a length of three feet.

MOLVA.--Differs from Lota in having several large teeth in the
lower jaw and on the vomer.

The “Ling” (_M. vulgaris_) is a very valuable species, common on the northern coasts of Europe, Iceland, and Greenland; and generally found from three to four feet long. The larger number of the specimens caught are cured and dried.

MOTELLA.--Body elongate, covered with minute scales. A separate
caudal. Two dorsal fins, the anterior of which is reduced to a
narrow rayed fringe, more or less concealed in a longitudinal
groove; the first ray is prolonged. One anal fin. Ventrals
composed of from five to seven rays. A band of teeth in the jaws
and on the vomer.

Eight species of “Rocklings” are known from the coasts of Europe, Iceland, Greenland, Japan, the Cape of Good Hope, and New Zealand. They are of small size, and chiefly distinguished by the number of their barbels. British are the Five-bearded Rockling (_M. mustela_), the Three-bearded Rocklings (_M. tricirrhata_, _macrophthalma_, and _maculata_), and the Four-bearded Rockling (_M. cimbria_). _M. macrophthalma_ comes from a depth of from 80 to 180 fathoms. The young are known as “Mackerel Midge” (_Couchia_), and sometimes met with in large numbers at some distance from the coast.

RANICEPS.--Head large, broad, and depressed; body of moderate
length, covered with minute scales. A separate caudal. Two
dorsal fins, the anterior of which is very short, rudimentary.
One anal fin. Ventrals composed of six rays. Cardlike teeth in
the jaws and on the vomer.

The “Trifurcated Hake,” _R. trifurcus_, not uncommon on the coasts of Northern Europe.

BREGMACEROS.--Body fusiform, compressed posteriorly, covered
with cycloid scales of moderate size. Two dorsal fins; the
anterior reduced to a single long ray on the occiput; the second
and the anal much depressed in the middle; ventrals very long,
composed of five rays. Teeth small.

A dwarf Gadoid, the only one found at the surface between the Tropics. _B. macclellandii_ scarcely exceeds three inches in length, is not uncommon in the Indian Ocean, and has found its way to New Zealand; specimens have been picked up in mid-ocean.

MURÆNOLEPIS.--Body covered with lanceolate epidermoid
productions, intersecting each other at right angles like those
of a Freshwater-eel. Vertical fins confluent, no caudal being
discernible; an anterior dorsal fin is represented by a single
filamentous ray; ventral fins narrow, composed of several rays.
A barbel. Jaws with a band of villiform teeth; palate toothless.

One species (_M. marmoratus_) from Kerguelen’s Land.

CHIASMODUS.--Body naked; stomach and abdomen distensible. Two
dorsal fins and one anal; a separate caudal; ventral fins rather
narrow, with several rays. Upper and lower jaws with two series
of large pointed teeth, some of the anterior being very large
and movable; teeth on the palatine bones, but none on the vomer.
Chin without barbel.

This Gadoid (_Ch. niger_, Fig. 111, p. 311), inhabits great depths in the Atlantic (to 1500 fathoms). The specimen figured was taken with a large Scopeloid in its stomach.

BROSMIUS.--Body moderately elongate, covered with very small
scales. A separate caudal, one dorsal, and one anal; ventrals
narrow, composed of five rays. Vomerine and palatine teeth. A
barbel.

The “Torsk” (_B. brosme_) is confined to the northern parts of the temperate zone, and probably extends to the arctic circle.

THIRD FAMILY--OPHIDIIDÆ.

_Body more or less elongate, naked, or scaly. Vertical fins generally united; no separate anterior dorsal or anal; dorsal occupying the greater portion of the back. Ventral fins rudimentary or absent, jugular. Gill-openings wide, the gill-membranes not attached to the isthmus._

Marine fishes (with the exception of _Lucifuga_), partly littoral, partly bathybial. They may be divided into five groups.

I. _Ventral fins present, attached to the humeral arch_: BROTULINA.

BROTULA.--Body elongate, covered with minute scales. Eye of
moderate size. Each ventral reduced to a single filament,
sometimes bifid at its extremity. Teeth villiform; snout with
barbels. One pyloric appendage.

Five species of small size from the Tropical Atlantic and Indian Ocean.

_Lucifuga_ are _Brotula_ organised for a subterranean life. The eye is absent, or quite rudimentary, and covered by the skin; the barbels of Brotula are replaced by numerous minute ciliæ or tubercles. They inhabit the subterranean waters of caves in Cuba, and never come to the light.

BATHYNECTES.--Body produced into a long tapering tail, without
caudal. Mouth very wide, villiform teeth in the jaws, on the
vomer and palatine bones. Barbel none. Ventral fins reduced to
simple or bifid filaments, placed close together, and near to
the humeral symphysis. Gill-membranes not united; gill-laminæ
remarkably short. Bones of the head soft and cavernous;
operculum with a very feeble spine above.

Deep-sea fishes, inhabiting depths varying from 1000 to 2500 fathoms. Three species are known, the largest specimen obtained being seventeen inches long.

ACANTHONUS.--Head large and thick, armed in front and on the
opercles with strong spines; trunk very short, the vent being
below the pectoral; tail thin, strongly compressed, tapering,
without caudal. Eye small. Mouth very wide; villiform teeth
in the jaws, on the vomer and palatine bones. Barbel none.
Ventrals reduced to simple filaments placed close together on
the humeral symphysis. Scales extremely small. Bones of the head
soft.

Only two specimens, thirteen inches long, of this remarkable deep-sea form have been obtained, at a depth of 1075 fathoms, in the Indian Ocean.

TYPHLONUS.--Head large, compressed, with most of the bones in
a cartilaginous condition; the superficial bones with large
muciferous cavities, not armed. Snout a thick protuberance
projecting beyond the mouth, which is rather small and inferior.
Trunk very short, the vent being below the pectoral; tail thin,
strongly compressed, tapering, without separate caudal. Eye
externally not visible. Villiform teeth in the jaws, on the
vomer and palatine bones. Barbel none. Scales thin, deciduous,
small.

Also of this deep-sea fish two specimens only are known, 10 inches long, from a depth of 2200 fathoms in the Western Pacific.

APHYONUS.--Head, body, and tapering tail strongly compressed,
enveloped in a thin, scaleless, loose skin. Vent far behind
the pectoral. Snout swollen, projecting beyond the wide
mouth. No teeth in the upper jaw, small ones in the lower. No
externally visible eye. Barbel none. Head covered with a system
of wide muciferous channels, the dermal bones being almost
membranaceous, whilst the others are in a semi-cartilaginous
condition. Notochord persistent, but with a superficial
indication of vertebral segments.

One specimen only of this most remarkable form is known; it is 5½ inches long, and was obtained at a depth of 1400 fathoms south of New Guinea.

Of the remaining genera belonging to this group, _Brotulophis_, _Halidesmus_, _Dinematichthys_, and _Bythites_ are surface forms; _Sirembo_ and _Pteridium_ inhabit moderate depths; _Rhinonus_ is a deep-sea fish.

II. _Ventral fins replaced by a pair of bifid filaments (barbels) inserted below the glossohyal_: OPHIDIINÆ.

OPHIDIUM.--Body elongate, compressed, covered with very small
scales. Eye of moderate size. All the teeth small.

Small fishes from the Atlantic and Pacific. Seven species are known, differing from one another in the structure of the air-bladder (see p. 145).

GENYPTERUS is a larger form of _Ophidium_, in which the outer
series of teeth in the jaws and the single palatine series
contains strong teeth.