An introduction to the natural history of fishes (Page 234) (6001873968)

234

ICHTHYOLOGY.

Chondrop- allied to Sq.c€ntrina,\)wt has conspicuous, ovate, hard, ca-

terygii. rinated scales.

belaehii. -j-j^g gj^jj,^ jjj^g jji^^ pj- jjjQgt other sharks, is rough, with

"^"^ numerous sharp granular eminences.

ScYMNUs, Cuv. This subdivision has all the charac-

teristics of Centrina, except the dorsal spines.

The European species is the Sq. Americaniis of Brous-

sonet and Shaw. It occurs on the coasts of France, off

Cape Breton, which lias been mistaken for the transatlan-

tic Cape Breton. It appears to be identical with Risso's

Sq. Nicensis.

The formidable animal described by O. Fabricius, in his

Fauna Groenlandica, as Sq. carcharias, is now, from the

descriptions of Scoresby and others, to be referred to this

sub-genus. It is Scoresby 's Sq. borealis. It wants the

anal fin, but has the temporal orifices. It grows to the

length of twelve or fourteen feet, and is six or eight in

circumference. Scoresby mentions the singular appen-

dages which he invariably found attached to the cornea of

this animal. Some have supposed them to be parasitic

animals. If so, it is singular that they should be so uni-

formly in the same position, and of the same size, about

one or two inches long, and cleft at their fore extremity

into two parts. This shark is peculiarly attracted by a

dead whale, out of which it scoops at once masses of

blubber as large as a man's head. The sailors believe

this species to be blind, from its returning to feed on its fa-

vourite morsel, even after having aflensingkniferun through

its body ; but this only shows its fondness for whale

blubber, — to which circumstance we may also attribute the

comparative safety of Greenland sailors who have fallen

into the water when flensing the whale. But, if we may

credit Fabricius, when this delectable food is not present,

he will attack the slender bark of the Greenlanders.

To this division belong also the Sq. spinosus and La-

bordii.

Genus Zyg^na, Cuv. This genus, which has the ge-

neral form of body and fins of Carcharias, is distinguished

by the extraordinary form of its head, that has no analogy

in nature, except in some of the insect tribe. It is flat-

tened horizontall.', truncated in front, and extended late-

rally into two arms, at the extremity of which are the

eyes, giving to the animal the form of a hammer. The

mouth is below the centre of this singular head, and the

nostrils at its anterior edges on each side. The most com-

mon in Europe is the .S'^'. zygcena, or hammer-headed

shark, which often attains the length of sixteen or seven-

teen feet, and is formidable on account of its voracity

and strength. It is found also around the West Indies,

and in the Indian Ocean, especially at Taheite, where the

natives are said, from their dexterity in swimming, to hold

it in little dread. It is a very prolific animal. Two kin-

dred species are known : the Sq. Blochii, Cuv., which dif-

fers in having the nostrils nearer the middle of the head,

and its two dorsals much nearer the tail ; and Sq. tiburo,

or heart-headed shark, a much rarer species, which we

have received from the coast of Guyana. We here figure

ZygcEna Leivinii, a species captured off the south coast of

New Holland. Plate CCCVII. fig. 5.

Genus Suuatina, Dumer. ; Angel-fish. Has the tem-

poral apertures without the anal fin ; but its mouth is ter-

minal, and its eyes are both placed on its dorsal surface, in

which it differs from all the sharks. The head and body

are flattened ; the pectoral fins are extremely broad, and

project forward to the sides of the head, but are separat-

ed from it and the neck by a fissure, in which the bran-

chial apertures are placed ; the two dorsals are behind the

ventrals, and the tail is equally finned above and below the

spinal column.

The best-known species is the Sq. squatina, Linn., or

angel-shark, which grows to eight or ten feet. It is a bold

and voracious fish ; when captured, it bites with great Chondrojv

fury ; it preys much on flat fish ; it has tentacula on its terygii.

upper lip ; its eyes, placed obliquely, give it a sinister look- Sela chiL

The English name has been given ironically to this hide-

ous creature, which is by seamen generally termed devil-

fish.

The teeth are slender, sharp, and dilated at their base ;

the dorsal fins very small, the pectorals very broad, the

ventral large, and enclosing the male organs. The upper

lobe of the tail longer than the lower. It is very prolific,

fourteen young being sometimes found in its belly ; twelve

frequently.

To this genus we raust also refer the Sq^ aculeatus of

the Mediterranean.

Genus Pristis, Lath. ; Saw-fish. This last genus has

the general form of the Squali, but is more flattened in

front, and has the branchial apertures beneath, like the

Rays. The most peculiar character, however, consists in

the great depression and extension of the snout, which

has on each side a row of strong teeth or spines, which

are trenchant on the fore-side, and mucronated. These

spines are not, however, their true teeth. These are

lodged in the mouth, and are very small and rounded.

But, with their formidable beak, they are said successfully

to attack the larger Cetacea. In the foetal Pristis the ru-

diments of these osseous spines are mere tubercles, and

the snout is folded up over the head of the embryon.

These spines are not, like the teeth of cartilaginous fishes,

attached by ligaments to the bones, but are firmly implant-

ed in the bone of the snout.

The best-known species is the Sq. pristis of Linn, or

Pristis antiqiiorum. It grows to a great size. We have

measured snouts more than ten inches in diameter, and

four feet seven inches in length, with sixteen or eighteen

spines on each side, some of which projected three inches.

The animal attains the length of sixteen or eighteen feet.

There are other species chiefly distinguished by the num-

ber and form of these spines : as Pristis cuspidatus, — Pr.

pectinatus, with numerous slender teeth, — Pr. microdon,

— P. cirratus, with alternate long and short teeth, — and

Pr. semi-sagittatus, a small Indian species, in which the

spines are deeply denticulated on the posterior edge.

Genus Raia (or Ray) of Linnaeus. This great genus of

the Selachii is very numerous, and the species often grow to

a vast size. They are readily recognised by their flattened

body, like the Pleuronectes, forming a horizontal disk, very

broad in proportion to its thickness, in consequence ofthe

body graduating into the enormous pectorals of the ani-

mal, which unite in front with the snout, and extend on

both sides of the abdomen to the base of the ventral

fins. See skeleton of the thorn-back (i?. clavata), Plate

CCCVII. fig. 9. The scapula of these vast pectorals are

articulated with the spine just behind the branchial aper-

tures. These apertures, the nostrils, and mouth, are on

the ventral surface of the fish ; the temporal orifices, and

the eyes, are on the dorsal surface. The dorsal fins are

usually placed on the tail. These animals are oviparous.

Their eggs are coriaceous, square, with long angles. The

subdivisions of Cuvier are the following.

Genus Rhinobatus, Sch. Distinguished by the length

of the snout ; connects the sharks and rays. They have a

thick and fleshy tail, like Squali, with two dorsal and two

caudal fins. Their snout and pectorals form a sharp rhom-

boid. Their teeth are placed in a quincunx arrangement.

In some the first dorsal is placed over the ventral fins, in

others it is placed farther back. The best known is the

IVIediterranean Raia rhinobatus, which is found four feet

in length. The others are, R. T/iouiniana (Plate CCCVII.

fig. 7), supposed by Cuvier a variety of that just named,

but it has such difference of form as to entitle it to be con-

sidered a distinct species ; R. djiddensis, Forsk. ; one de-

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