XAM Idea Mathematics CBSE Class 10
2024th Edition Xam Idea
Visit to download the full and correct content document: https://textbookfull.com/product/xam-idea-mathematics-cbse-class-10-2024th-editionxam-idea/
More products digital (pdf, epub, mobi) instant download maybe you interests ...
XAM Idea Science Class 10 2024th Edition Xam Idea
https://textbookfull.com/product/xam-idea-scienceclass-10-2024th-edition-xam-idea/
XAM IDEA Mathematics Sample Paper Class 10 2023 2024th Edition Xam Idea
https://textbookfull.com/product/xam-idea-mathematics-samplepaper-class-10-2023-2024th-edition-xam-idea/
XAM Idea Social Science Class 10 2024th Edition Xam Idea
https://textbookfull.com/product/xam-idea-social-scienceclass-10-2024th-edition-xam-idea/
Xam Idea Class 12 Chemistry Sample Papers 2023 2024th Edition Xam Idea
https://textbookfull.com/product/xam-idea-class-12-chemistrysample-papers-2023-2024th-edition-xam-idea/
XamIdea Mathematics Class 12 2024 2024th Edition Xam Idea
https://textbookfull.com/product/xamidea-mathematicsclass-12-2024-2024th-edition-xam-idea/
XAM IDEA Science Sample Papers Class 10 2023 2023rd Edition Xam Idea
https://textbookfull.com/product/xam-idea-science-sample-papersclass-10-2023-2023rd-edition-xam-idea/
XAM IDEA Social Science Sample Papers Class 10 2023 2023rd Edition Xam Idea
https://textbookfull.com/product/xam-idea-social-science-samplepapers-class-10-2023-2023rd-edition-xam-idea/
XamIdea Chemistry Class 12 2024 2024th Edition Xam Idea
https://textbookfull.com/product/xamidea-chemistryclass-12-2024-2024th-edition-xam-idea/
XamIdea Physics Class 12 2024 2024th Edition Xam Idea
https://textbookfull.com/product/xamidea-physicsclass-12-2024-2024th-edition-xam-idea/
Another random document with no related content on Scribd:
Fig. 219. Young of Cyclopterus spinosus, from the Arctic Ocean, natural size.
L —Body sub-cylindrical, enveloped in a more or less loose naked skin; head broad, obtuse. The infraorbital bone is styliform posteriorly, extending backwards to the margin of the præoperculum. One dorsal fin, with feeble flexible rays. Villiform teeth in the jaws, none on the palate.
Small fishes from the northern coasts of the temperate zone, ranging beyond the arctic circle. Eight species are known, of which two (L. lineatus and L. montagui) occur on the British coasts.
S F —G .
Body elongate, naked or scaly. Teeth generally small, sometimes with canines. The spinous dorsal fin, or portion of the dorsal fin, is the less developed, and composed of flexible spines; anal similarly developed as the soft dorsal. Sometimes the ventrals are united into a disk. Gill-opening more or less narrow, the gill-membranes being attached to the isthmus.
Small carnivorous littoral fishes, many of which have become acclimatised in fresh water. They are very abundant with regard to species as well as individuals, and found on or near the coasts of all temperate and tropical regions. Geologically they appear first in the chalk.
G . Body scaly. Two dorsal fins, the anterior generally with six flexible spines. Ventral fins united, forming a disk which is not attached to the abdomen. Gill-opening vertical, moderately wide.
220 Gobius lentiginosus, from New Zealand
The “Gobies” are distributed over all temperate and tropical coasts, and abundant, especially on the latter Nearly three hundred species have been described. They live especially on rocky coasts, attaching themselves firmly with their ventrals to a rock in almost any position, and thus withstanding the force of the waves. Many of the species seem to delight in darting from place to place in the rush of water which breaks upon the shore. Others live in quiet brackish water, and not a few have become entirely acclimatised in fresh water, especially lakes. The males of some species construct nests for the eggs, which they jealously watch, and defend even for some time after the young are hatched. Several species are found on the British coast: G. niger, paganellus, auratus, minutus, ruthensparri. Fossil species of this genus have been found at Monte Bolca.
A very small Goby, Latrunculus pellucidus, common in some localities of the British Islands and other parts of Europe, is distinguished by its transparent body, wide mouth, and uniserial dentition. According to R. Collett it offers some very remarkable peculiarities. It lives one year only, being the first instance of an annual vertebrate. It spawns in June and July, the eggs are hatched in August, and the fishes attain their full growth in the months from October to December. In this stage the sexes are quite alike, both having very small teeth and feeble jaws. In April the males lose the
small teeth, which are replaced by very long and strong teeth, the jaws themselves becoming stronger. The teeth of the females remain unchanged. In July and August all the adults die off, and in September only the fry are to be found.
There are several other genera, closely allied to Gobius, as Euctenogobius, Lophiogobius, Doliichthys, Apocryptes, Evorthodus, Gobiosoma and Gobiodon (with scaleless body) Triænophorichthys.
S . Body covered with ctenoid scales of rather small size. Cleft of the mouth nearly horizontal, with the upper jaw prominent; lips very thick; the lower lip generally with a series of minute horny teeth. A series of numerous small teeth in upper jaw, implanted in the gum, and generally movable; the lower jaw with a series of conical widelyset teeth. Two dorsal fins, the anterior with six flexible spines. Ventral fins united, and forming a short disk, more or less adherent to the abdomen.
Small freshwater fishes inhabiting the rivers and rivulets of the islands of the tropical Indo-Pacific. About twelve species are known; one occurs in the West Indies. Lentipes from the Sandwich Islands is allied to Sicydium.
P . Body covered with ctenoid scales of small or moderate size. Cleft of the mouth nearly horizontal, with the upper jaw somewhat longer Eyes very close together, immediately below the upper profile, prominent, but retractile, with a well-developed outer eyelid Teeth conical, vertical in both jaws Two dorsal fins, the anterior with flexible spines; caudal fin with the lower margin oblique; base of the pectoral fin free, with strong muscles Ventral fins more or less coalesced Gill-openings narrow
The fishes of this genus, and the closely-allied Boleophthalmus, are exceedingly common on the coasts of the tropical Indo-Pacific, especially on parts covered with mud or fucus. During ebb they leave the water and hunt for small crustaceans, and other small animals disporting themselves on the ground which is left uncovered by the receding water. With the aid of their strong pectoral and ventral fins and their tail, they hop freely over the ground, and escape danger by rapid leaps. The peculiar construction of their eyes, which are very movable, and can be thrust far out of their sockets, enables them to see in the air as well as in the water; when the eyes are retracted
they are protected by a membranous eyelid. These fishes are absent in the eastern parts of the Pacific and on the American side of the Atlantic; but singularly enough one species reappears on the West African coast. About seven species are known (including Boleophthalmus), P. koelreuteri being one of the most common fishes of the Indian Ocean.
E . Body scaly; eyes of moderate size, lateral, not prominent. Teeth small. Two dorsal fins, the anterior generally with six spines. Ventrals not united, though close together, with one spine and five rays.
About sixty species are known from the tropics, only a few extending into the temperate zone. As regards form, they repeat almost all the modifications observed among the Gobies, from which they differ only in having the ventral fins non-coalescent. On the whole they are somewhat larger than the Gobies, and rather freshwater than marine species, some of them being abundant in the rivulets of the islands of the Indo-Pacific and Atlantic. Others have even penetrated into the inland-waters of the African continent.
T . Body elongate, covered with minute scales; head compressed, with a deep cavity on each side, above the operculum. Teeth small, in a band. One dorsal, the spinous portion composed of six spines; dorsal and anal fins continuous with the caudal, ventral fins united
Small fishes of singular aspect, from the East Indian coasts. Three species, of which T. vagina is common.
C . Head and anterior part of the body depressed, the rest cylindrical, naked. Snout pointed, with the cleft of the mouth narrow, horizontal, and with the upper jaw very protractile. Eyes rather large, more or less directed upwards Teeth very small, palate smooth
A strong spine at the angle of the præoperculum Two dorsal fins, the anterior with three or four flexible spines; ventrals five-rayed, widely apart from each other Gill-openings very narrow, generally reduced to a foramen on the upper side of the operculum
The “Dragonets” are small, and generally beautifully coloured marine fishes, inhabitants of the coasts of the temperate zone of the Old World; the minority of species live in tropical parts of the IndoPacific; and these seem to descend to somewhat greater depths than the littoral species of the northern hemisphere. Secondary sexual characters are developed in almost all the species, the mature males having the fin-rays prolonged into filaments, and the fin-membranes brightly ornamented. On the British coast one species (C. draco) is very common, and locally called “Skulpin.” About thirty species are known, many of which have the præopercular spine armed with processes or barbs. Vulsus is allied to Callionymus.
Other genera belonging to this family are—Benthophilus from the Caspian Sea; Amblyopus, Orthostomus, Platyptera, Luciogobius, Oxymetopon, and, perhaps, Oxuderces.
T D —A B .
Body low, sub-cylindrical or compressed, elongate. Dorsal fin very long; the spinous portion of the dorsal, if distinct, is very long, as well developed, as the soft, or much more; sometimes the entire fin is composed of spines only; anal more or less long; caudal fin subtruncated or rounded, if present. Ventral fins thoracic or jugular, if present.
F F —C .
Body very elongate, compressed, covered with very small cycloid scales; eyes rather large, lateral. Teeth of moderate size. No bony stay for the angle of the præoperculum. One very long dorsal fin, which, like the anal, is composed of soft rays. Ventrals thoracic, composed of one spine and five rays. Gill-opening wide. Caudal vertebræ exceedingly numerous.
The “Band-fishes” (Cepola) are small marine fishes, belonging principally to the fauna of the northern temperate zone; in the Indian Ocean the genus extends southwards to Pinang. The European species (C. rubescens) is found in isolated examples on the British coast, but is less scarce in some years than in others. These fishes are of a nearly uniform red colour.
S F —T .
Body elongate, sub-cylindrical, covered with cycloid scales of moderate size. Eyes directed upwards. Teeth in villiform bands. No bony stay for the angle of the præoperculum. One long dorsal fin, with simple articulated rays, and without a spinous portion; anal long. Ventrals jugular, with one spine and five rays. Gill-opening very wide. The number of caudal vertebræ much exceeding that of the abdominal.
Small marine fishes, belonging to two genera only, Trichonotus (setigerus) from Indian Seas, with some of the anterior dorsal rays prolonged into filaments; and Hemerocoetes (acanthorhynchus) from New Zealand, and sometimes found far out at sea on the surface.
T F —H .
Body oblong, compressed, scaly; eyes lateral; cleft of the mouth lateral; dentition feeble. The angle of the præoperculum connected by a bony stay with the infraorbital ring. Dorsal long, with the spinous and soft portions equally developed; anal elongate. Ventrals thoracic, with one spine and five rays.
Fig. 222. Scale from the lateral line of Hemerocœtes acanthorhynchus, with lacerated margin.
223
Small shore-fishes, characteristic of the fauna of the Northern Pacific, some of the species occurring on the American as well as Asiatic side. They have been referred to several genera, as C , which is distinguished by the presence of several lateral lines;
O , with one lateral line only, cycloid scales, and slightly armed præoperculum;
A , with one lateral line only, ctenoid scales, and unarmed præoperculum; and
Z , with one lateral line and minute comb-like scales.
Body elongate, low, more or less cylindrical, naked or covered with scales, which generally are small. One, two, or three dorsal fins occupying nearly the whole length of the back, the spinous portion, if distinct, being as much developed as the soft, or more; sometimes the entire fin is composed of spines; anal fin long. Ventrals jugular, composed of a few rays, and sometimes rudimentary or entirely absent. Pseudobranchiæ generally present.
Littoral forms of great generic variety, occurring abundantly in all temperate and tropical seas. Some of the species have become acclimatised in fresh water, and many inhabit brackish water. With very few exceptions they are very small, some of the smallest fishes belonging to the family of “Blennies.” One of the principal characteristics of the Blennies is the ventral fin, which is formed by less than five rays, and has a jugular position. The Blennies have this in common with many Gadoids, and it is sometimes difficult to decide to which of these two families a fish should be referred. In such doubtful cases the presence of the pseudobranchiæ (which are absent in Gadoids) may be of assistance.
In many Blennies the ventral fins have ceased to have any function, and become rudimentary, or are even entirely absent. In others the ventral fins, although reduced to cylindrical stylets, possess a distinct function, and are used as organs of locomotion, by the aid of which the fish moves rapidly over the bottom.
The fossil forms are scarcely known; Pterygocephalus from Monte Bolca appears to have been a Blennioid.
A —Body elongate, with rudimentary scales; snout rather short; cleft of the mouth wide; strong conical teeth in the jaws, those on the sides with several pointed tubercles; a biserial band of large molar teeth on the palate. Dorsal fin long, with flexible spines; caudal separate. Ventrals none. Gill-openings wide.
The “Sea-wolf,” or “Sea-cat” (A. lupus), is a gigantic Blenny, attaining to a length of more than six feet. With its enormously strong tubercular teeth it is able to crush the hardest shells of Crustaceans or Mollusks, on which it feeds voraciously. It is an inhabitant of the
northern seas, like two other allied species, all of which are esteemed as food by the inhabitants of Iceland and Greenland. Two other species of Sea-wolves occur in the corresponding latitudes of the North Pacific.
Fig. 224. Teeth of the Wolf-fish, Anarrhichas lupus.
B Body moderately elongate, naked; snout short A single dorsal, without detached portion; ventrals jugular, formed by a spine and two rays Cleft of the mouth narrow; a single series of immovable teeth in the jaws; generally a curved tooth behind this series in both jaws, or in the lower only A more or less developed tentacle above the orbit Gill-opening wide
About forty species of Blennius (in the restricted generic sense) are known from the northern temperate zone, the tropical Atlantic, Tasmania, and the Red Sea. But in the tropical Indian Ocean they are almost entirely absent, and replaced by other allied genera. Three species, found near the Sandwich Islands, are immigrants into the Pacific from the American Continent. They generally live on the coast, or attach themselves to floating objects, some species leading a pelagic life, hiding themselves in floating seaweed, in which they even propagate their species. All species readily accustom themselves to fresh water, and some (B. vulgaris) have become entirely acclimatised in inland lakes. British species are B.
gattorugine (growing to a length of twelve inches), B. ocellaris, B. galerita, and B. pholis, the common “Shanny.”
Chasmodes is a genus allied to Blennius, from the Atlantic coasts of temperate North America.
Fig. 225. Petroscirtes bankieri, from Hong-Kong.
P Body moderately elongate, naked Snout generally short A single dorsal fin; ventrals composed of two or three rays Cleft of the mouth narrow; a single series of immovable teeth in the jaws; a strong curved canine tooth behind this series, that of the lower jaw much stronger than that of the upper Head sometimes with tentacles Gill-opening reduced to a small fissure above the root of the pectoral.
Thirty species, from the tropical Indo-Pacific, of small size.
Fig. 226. Dentition of the same, enlarged.
S . Body moderately elongate, naked; snout short, with transverse cleft of the mouth; a series of numerous small teeth in the jaws, implanted in the gum and movable; generally a curved canine tooth on each side of the lower jaw, behind the series of small teeth Dorsal fin continuous, sometimes divided into two portions by a more or less deep notch without a detached anterior part Ventral fins with two or three rays A tentacle above the orbit Gill-openings wide
Sixty species are known from the tropical zone, extending northwards to Madeira, southwards to Chile and Tasmania. In certain individuals of some of the species a longitudinal cutaneous crest is developed; all young individuals lack it, and in some other species it is invariably absent. Singularly enough this crest is not always a sexual character, as one might have supposed from analogy, but in some species at least it is developed in both sexes. Mature males, however, have generally higher dorsal fins and a more intense and variegated coloration than females and immature males, as is also the case in Blennius.
C . Body moderately elongate, covered with small scales; snout rather short; a narrow band or series of small teeth in the jaws and on the palate. Dorsal fin formed by numerous spines and a few soft rays, without a detached anterior portion; anal spines two. Ventrals with two or three rays. A tentacle above the orbit. Gillopening wide.
Thirty species, from the coasts of tropical America and the southern temperate zone. Three other genera are closely allied to Clinus, viz. Cristiceps and Cremnobates, in which the three anterior dorsal spines are detached from the rest of the fin; and Tripterygium, with three distinct dorsal fins, of which the two anterior are spinous. The species of these genera are as numerous as those of Clinus, occurring in many parts of tropical seas, in the Mediterranean, and being especially well represented in South Australia and New Zealand.
S . Body elongate, covered with very small scales; lateral line more or less distinct, sometimes several lateral lines Snout short; very small teeth in the jaws, and generally on the palate Dorsal fin long, formed by spines only Ventrals with two or three rays Caudal fin distinct Gill-openings rather wide
Small fishes, peculiar to the coasts near the arctic circle, ranging southwards to the coasts of Japan and Scandinavia. Ten species.
B . Body moderately elongate, covered with very small scales; lateral line none. Snout short; small teeth in the jaws, none on the palate. Dorsal fin long, formed by spines only. Ventrals with one spine and three rays Caudal distinct Gill-openings of moderate width, the gill-membranes coalescent across the isthmus
A fine but not common kind of Blenny (B. ascanii), from the British and Scandinavian coasts.
C . Body elongate, covered with very small scales; lateral line none. Snout short; very small teeth in the jaws. Dorsal fin long, formed by spines only. Ventrals none or rudimentary; caudal separate. Gill-openings of moderate width, gill-membranes coalescent.
Ten species are known from the northern coasts; southwards the genus extends to the coasts of France, New York, California, and Japan. C. gunellus, or the “Gunnel-fish” or “Butter-fish,” is common on the British coasts. Apodichthys is allied to Centronotus, but the vertical fins are confluent; and a very large, excavated, pen-like spine lies hidden in a pouch in front of the anal fin. This spine is evidently connected in some way with the generative organs, as a furrow leads from the orifice of the oviduct to the groove of the spine. One species from the Pacific coast of North America. Xiphidion is another closely allied genus from the same locality.
C Body very elongate, naked, with a single lateral line Head with the muciferous system well developed Eye rather small Conical teeth in the jaws, on the vomer and palatine bones One dorsal formed by spines only; caudal connected with dorsal and anal. Ventrals none. Gill-opening of moderate width, with the gill-membranes joined to the isthmus.
One species (C. maculatus) from the Atlantic coasts of North America.
P Body oblong, elevated anteriorly; snout short, with subvertical anterior profile; minute teeth in the jaws and on the vomer Dorsal fin with the anterior spines strong and long, continuous with the caudal; ventrals none Gill-openings wide
Three species of this singular form are known from South and West Australia.
Z . Body elongate, with the scales rudimentary; conical teeth in the jaws. Dorsal fin long, with a depression on the tail, which is formed by a series of spines much shorter than the rays. No other fin-spines. No separate caudal fin. Ventrals short, formed by three or four rays. Gill-openings wide.
Two species are known, one from the European, and the other from the North American side of the Atlantic. The former, Z. viviparus, is well known by the name of “Viviparous Blenny;” as is signified by this name it produces its young alive. These are so matured at the time of their birth that on their first exclusion they swim about with the utmost agility. No fewer than from two to three hundred young are sometimes produced by one female, and the abdomen of the mother is so distended before parturition that it is impossible to touch it without causing them to be extruded. Full grown individuals are about twelve inches long, but the American species (Z. anguillaris) attains to a length of two or three feet.
Other genera of the family of Blennoids are:—Blennophis, Nemophis, Plagiotremus, Neoclinus, Cebidichthys, Myxodes, Heterostichus, Dictyosoma, Lepidoblennius, Dactyloscopus, Gunellichthys, Urocentrus, Stichæopsis, Sticharium, Notograptus, Pholidichthys, and Pseudoblennius.
F F —A
Body elongate, low, compressed, covered with small scales. One dorsal fin, occupying nearly the whole of the back, and chiefly composed of spines. Anal fin long, with numerous spines. Ventrals jugular, composed of a few rays only.
Of this family one fish only is known (Acanthoclinus littoreus), a small Blenny abundant on the coast of New Zealand.
S F —M .
Body elongate, eel-like, covered with very small scales. Mandible long, but little moveable. Dorsal fin very long, the anterior portion composed of numerous short isolated spines; anal fin with spines anteriorly. Ventrals none. The humeral arch is not suspended from the skull. Gill-openings reduced to a slit at the lower part of the side of the head.
Freshwater-fishes characteristic of and almost confined to the Indian region. The structure of the mouth and of the branchial apparatus, the separation of the humeral arch from the skull, the absence of ventral fins, the anatomy of the abdominal organs, affords ample proof that these fishes are Acanthopterygian eels. Their upper jaw terminates in a pointed moveable appendage, which is concave and transversely striated inferiorly in Rhynchobdella, and without transverse striæ in Mastacembelus: the only two genera of this family. Thirteen species are known, of which Rh. aculeata, M. pancalus and M. armatus are extremely common, the latter attaining to a length of two feet. Outlying species are M. aleppensis from Mesopotamia and Syria, and M. cryptacanthus, M. marchei, and M. niger, from West Africa.
E D —A M
Two dorsal fins more or less remote from each other; the anterior either short, like the posterior, or composed of feeble spines. Ventral fins with one spine and five rays, abdominal.
F F —S .
Body elongate, sub-cylindrical, covered with small cycloid scales; lateral line continuous. Cleft of the mouth wide, armed with strong teeth. Eye lateral, of moderate size. Vertebræ twenty-four.
This family consists of one genus only, Sphyræna, generally called “Barracudas,” large voracious fishes from the tropical and subtropical seas, which prefer the vicinity of the coast to the open sea. They attain to a length of eight feet, and a weight of forty pounds; individuals of this large size are dangerous to bathers. They are generally used as food, but sometimes (especially in the West Indies) their flesh assumes poisonous qualities, from having fed on smaller poisonous fishes. Seventeen species.
The Barracudas existed in the tertiary epoch, their remains being frequently found at Monte Bolca. Some other fossil genera have been associated with them, but as they are known from jaws and teeth or vertebræ only, their position in the system cannot be exactly determined; thus Sphyrænodus and Hypsodon from the chalk of Lewes, and the London clay of Sheppey. The American Portheus is allied to Hypsodon. Another remarkable genus from the chalk, Saurocephalus, has been also referred to this family.[44]
S F —A .
Body more or less elongate, sub-cylindrical, covered with scales of moderate size; lateral line indistinct. Cleft of the mouth of moderate width, with the dentition feeble. Eye lateral, large or of moderate size. Gill-openings wide. Vertebræ very numerous.
Small carnivorous fishes inhabiting the seas of the temperate and tropical zones; many enter fresh water, and some have been entirely acclimatised in it. This family seems to have been represented in the Monte Bolca formation by Mesogaster.
A Teeth very small; scales cycloid The first dorsal is short and entirely separated from the second Snout obtuse, with the cleft of the mouth straight, oblique, extending to or beyond the anterior margin of the eye.
The Atherines are littoral fishes, living in large shoals, which habit has been retained by the species acclimatised in fresh water. They rarely exceed a length of six inches, but are nevertheless esteemed as food. From their general resemblance to the real Smelt they are often thus misnamed, but may always be readily recognised by their small first spinous dorsal fin. The young, for some time after they are hatched, cling together in dense masses, and in numbers almost incredible. The inhabitants of the Mediterranean coast of France call these newly hatched Atherines “Nonnat” (unborn). Some thirty species are known, of which A. presbyter and A. boyeri occur on the British coast.
A , distinguished from Atherina in having the snout more or less produced; and the cleft of the mouth generally does not extend to the orbit
These Atherines are especially abundant on the coasts and in the fresh waters of Australia and South America. Of the twenty species known, several attain a length of eighteen inches and a weight of more than a pound. All are highly esteemed as food; but the most celebrated is the “Pesce Rey” of Chile (A. laticlavia).
T —Body rather elongate, covered with strongly keeled and striated scales. The first dorsal fin is composed of numerous feeble spines, and continued on to the second. Lower jaw elevated, with convex dental margin, and armed with compressed, triangular, rather small teeth, in a single series.
This very remarkable fish is more frequently met with in the Mediterranean than in the Atlantic, but generally scarce. Nothing is known of its habits; when young it is one of the fishes which accompany Medusæ, and, therefore, it must be regarded as a
pelagic form. Probably, at a later period of its life, it descends to greater depths, coming to the surface at night only. It grows to a length of eighteen inches.
T F —M .
Body more or less oblong and compressed, covered with cycloid scales of moderate size; lateral line none. Cleft of the mouth narrow or of moderate width, without or with feeble teeth. Eye lateral, of moderate size. Gill-opening wide. The anterior dorsal fin composed of four stiff spines. Vertebræ twenty-four.
The “Grey Mullets” inhabit in numerous species and in great numbers the coasts of the temperate and tropical zones. They frequent brackish waters, in which they find an abundance of food which consists chiefly of the organic substances mixed with mud or sand; in order to prevent larger bodies from passing into the stomach, or substances from passing through the gill-openings, these fishes have the organs of the pharynx modified into a filtering apparatus. They take in a quantity of sand or mud, and, after having worked it for some time between the pharyngeal bones, they eject the roughest and indigestible portion of it. The upper pharyngeals have a rather irregular form; they are slightly arched, the convexity being directed towards the pharyngeal cavity, tapering anteriorly and broad posteriorly. They are coated with a thick soft membrane, which reaches far beyond the margin of the bone, at least on its interior posterior portion; this membrane is studded all over with minute horny cilia. The pharyngeal bone rests upon a large fatty mass, giving it a considerable degree of elasticity. There is a very large venous sinus between the anterior portion of the pharyngeal and the basal portion of the branchial arches. Another mass of fat, of elliptical form, occupies the middle of the roof of the pharynx, between the two pharyngeal bones. Each branchial arch is provided on each side, in its whole length, with a series of closely-set gillrakers, which are laterally bent downwards, each series closely fitting into the series of the adjoining arch; they constitute together a
sieve, admirably adapted to permit a transit for the water, retaining at the same time every other substance in the cavity of the pharynx.
The lower pharyngeal bones are elongate, crescent-shaped, and broader posteriorly than anteriorly. Their inner surface is concave, corresponding to the convexity of the upper pharyngeals, and provided with a single series of lamellæ, similar to those of the branchial arches, but reaching across the bone from one margin to the other.
The intestinal tract shows no less peculiarities. The lower portion of the œsophagus is provided with numerous long thread-like papillæ, and continued into the oblong-ovoid membranaceous cœcal portion of the stomach, the mucosa of which forms several longitudinal folds. The second portion of the stomach reminds one of the stomach of birds; it communicates laterally with the other portion, is globular, and surrounded by an exceedingly strong muscle. This muscle is not divided into two as in birds, but of great thickness in the whole circumference of the stomach, all the muscular fasciculi being circularly arranged. The internal cavity of this stomach is rather small, and coated with a tough epithelium, longitudinal folds running from the entrance opening to the pyloric, which is situated opposite to the other. A low circular valve forms a pylorus. There are five rather short pyloric appendages. The intestines make a great number of circumvolutions, and are seven feet long in a specimen thirteen inches in length.
Fig. 229. Mugil proboscideus.
Some seventy species of Grey Mullets are known, the majority of which attain to a weight of about four pounds, but there are many which grow to ten and twelve pounds. All are eaten, and some even esteemed, especially when taken out of fresh water. If attention were paid to their cultivation, great profits could be made by fry being transferred into suitable backwaters on the shore, in which they rapidly grow to a marketable size. Several species are more or less abundant on the British coasts, as Mugil octo-radiatus (Fig. 105, p. 254), M. capito, M. auratus (Fig. 106, p. 254), and M. septentrionalis (Fig. 107, p. 254), which, with the aid of the accompanying figures, and by counting the rays of the anal fin, may be readily distinguished —M. octo-radiatus having eight, and M. capito and M. auratus nine soft rays. A species inhabiting fresh waters of Central America (M. proboscideus) has the snout pointed and fleshy, thus approaching certain other freshwater and littoral Mullets, which, on account of a modification of the structure of the mouth, have been formed into a distinct genus, Agonostoma. Myxus comprises Mullets with teeth more distinct than in the typical species.
This genus existed in the tertiary epoch, remains of a species having been found in the gypsum of Aix, in Provence.
T D —A G .
The spinous dorsal is composed of isolated spines if present; the ventrals are either thoracic or have an abdominal position in consequence of the prolongation of the pubic bones which are attached to the humeral arch. Mouth small, at the end of the snout which is generally more or less produced.
F F —G .
Body elongate, compressed. Cleft of the mouth oblique; villiform teeth in the jaws. Opercular bones not armed; infraorbitals covering the cheek; parts of the skeleton forming incomplete external mails. Scales none, but generally large scutes along the side. Isolated spines in front of the soft dorsal fin. Ventral fins abdominal, joined to the pubic bone, composed of a spine and a small ray. Branchiostegals three.
230. Gastrosteus noveboracensis.
Of “Sticklebacks” (Gastrosteus) about ten species are satisfactorily known, one of which (G. spinachia) lives in salt and brackish water, whilst the others inhabit principally fresh waters, although they all are able to exist in the sea. They are confined to the Temperate and Arctic zones of the northern hemisphere. The British freshwater species are the Three-spined Stickleback (G. aculeatus), which sometimes, especially in Central Europe, lacks scutes, sometimes has a series of scutes along the side of the body; the Four-spined Stickleback (G. spinulosus) and the Nine-spined Stickleback (G. pungitius). The commonest North American species