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conformation more to the typical sharks than to the rays, yet in the structure of
their vertebrae they agree with the latter. Accordingly, both the spiny dog-fishes,
rays, saw-fishes, and their kindred are regarded as forming a suborder (Tecto-
spondyli) distinguished from the one including the preceding families by the
following characters. In the bodies of the vertebras, when fully developed, the
concentric calcified plates are more numerous than those radiating from the centre ;



534 SHARKS AND RAYS.

and the anal fin is invariably wanting. In the more specialised forms the body is
greatly developed, and the pectoral fins attain an enormous development ; while the
spiracles are of large size, and always retained. The present family includes the
most generalised members of the group, in which the body is cylindrical or
triangular, and but very slightly depressed ; the mouth being gently arched, and
the muzzle blunt. The pectoral fins have no forward prolongation, and are not
notched at their point of origin; and the small and lateral gill-clefts may be
either in the line of the pectorals, or half below. The large spiracles are placed
behind the eyes ; there is no nictitating membrane to the eye ; and the two dorsal
fins may or may not be provided with spines.

The common spiny, or picked, dog-fish (Acanthias vulgaris),
' shown in the upper figure of the illustration on p. 525, is the most
familiar representative of a very small genus characterised by the presence of
spines to the dorsal fins, and by the peculiar form of the teeth, which are similar
in the two jaws, and small, triangular, and compressed, with the points much turned
aside, and the cutting-edge formed by the inner margin. The common species
measures from 3 to 4 feet in length, and is slaty blue above, and yellowish white
beneath. It is very abundant on the British coasts, sometimes making its appear-
ance in such incredible numbers that upwards of twenty thousand were once
captured in a single haul on the Cornish coast. In common with an allied species
(A. blainvillei), this dog-fish presents the peculiarity of inhabiting the two
temperate zones but being unknown in the intervening tropical seas. The eggs
are hatched within the body of the female, and a considerable number of young
are produced at a birth. Somewhat dangerous wounds result from the spines.

Among other types, we may notice the genus Centrophorus,
represented by eight European species, and a ninth from the Moluccas,
all of which differ from the last by the upper teeth being erect and spear-like, with
a single cusp ; the dorsal spines being often very small. Apparently not exceeding
5 feet in length, these sharks are noteworthy on account of the depth at which
they live ; one of the species being caught with lines at a depth of from three to
four hundred fathoms off the coast of Portugal. When hauled up, these fish are
quite dead, owing to the diminished pressure. A fossil species occurs in the Chalk
of Syria. In the typical genus Spinax the teeth in the two jaws are likewise
dissimilar; but those of the lower one are broader than in the last, although with

' ' O

the points similarly turned aside. The genus is now represented by three small
species from the Atlantic and the extremity of South America; but has been
recorded from the Miocene Tertiary. The Greenland shark (Lcvmdrgus borcalis)
of the Arctic seas, which occasionally strays as far south as Britain, represents
another genus characterised by the small size of all the fins and the want of spines
to the dorsals, the first of which is situated considerably in advance of the pelvic
pair; the skin being uniformly covered with small tubercles. In the upper jaw
the teeth are small, narrow, and conical: but those of the lower jaw. which art
numerous and form several series, have their points so much bent to one side that
their inner margins form the cutting-edge, which is not serrated. (Jrowingtoa
length of 15 feet, the Greenland shark is a determined enemy to the right whale
of the same seas ; and when feeding on the carcase of one of those mammals



ANGEL- AND SAW-FISHES. 535

becomes so intent on its occupation as to allow itself to be harpooned without
attempting to escape. Four living young are stated to be produced at a birth.
Finally, we have the spiny shark (Eckinorhinus spinosus) of the Mediterranean
and Atlantic, which while agreeing with the last in the small size of the fins and
the absence of spines to the dorsals, differs by the teeth being alike in both jaws,
and by the presence of large rounded tubercles scattered over the skin ; the body
being very bulky, and the tail short. This shark lives at considerable depths, and
but rarely comes to the surface.

THE EXTINCT PETALODONTS, Family PETALOHONTID^E.

The extinct genera Petalodus and Janassa, together with several other allied
types from the Carboniferous rocks, represent a family apparently connecting the
last with the more typical rays. In these fishes the body is moderately depressed,
and the pectoral fins are large and continued anteriorly towards the head. The
teeth, which generally have large roots, are compressed from front to back, with the
crown more or less bent backwards, and either with a sharp cutting-edge, or very
blunt. In the mouth they were arranged in straight rows to form a pavement.

THE ANGEL-FISH, Family SQUATINID^E.

The sole existing representative of its family, the angel-fish, or monk-fish
(Squatina vulgar is), constitutes, so far as external form is concerned, a kind of
connecting link between the sharks and the rays. Having the body as much
depressed as in some of the latter, the angel-fish differs in the nearly terminal
position of the mouth, and also in the circumstance that while the basal portion of
the pectoral fins is much produced forwards, it does not extend so far as to join
the head. The wide gill-clefts are lateral in position, and partly covered by the
base of the pectoral fins ; the spiracles are wide and placed behind the eyes ; and
the teeth are conical and pointed. Spines are wan ting to the dorsal fins, which are
situated on the tail ; and the skin is studded with tubercles. Not unfrequently
growing to a length of at least 5 feet, the angel-fish has an almost cosmopolitan
distribution, and is by no means uncommon on the British coasts, more especially
in Scotland. In colour it is mottled chocolate-brown above, and whitish beneath,
and except that it produces living young, which may number as many as
twenty at a birth, its general habits are similar to those of the rays. Fossil
species of angel-fish range through the Tertiary and Cretaceous strata to the
upper Jurassic.

THE SAW-FISHES, Families PRISTIOPHORID^; and PRISTID&

Unique among the whole class on account of the production of the upper jaw
into a long flattened beak, furnished on either edge with a series of large, sharp,
and pointed teeth, set in distinct sockets at a considerable distance from one
another, the saw-fishes form two well-defined families, the first of which approxi-
mates to the sharks in the position of the gill-clefts, while the second agrees with



536



SHARKS AND RAYS.



the rays in the same particular. Each contains but a single existing genus, and
the first is unknown previous to the present epoch.

Side-Giiied The four species belonging to the first family, one of which

saw-Fishes. (Pristiophorus japonicus) is shown in the illustration, are com-
paratively small fishes confined to the Japanese and Australian seas. Having the
body scarcely depressed, and the pectoral fins of moderate dimensions, and not




ANGEL-FISH ( T \ nat. size).

extending forwards to the head, these saw-fishes are distinguished by the lateral
position of the gill-clefts, and full development of the so-called prepalatinc
cartilage, and the presence of a pair of long tentacles on (lie lower aspect of the
jaw. In habits these fishes probably resemble those of the next genus.

Distributed over all the warmer seas, the members of this genus,
among which /V/W/'x a nf /quorum, ot the Mediterranean and Atlantic
is most commonly met with, differ from the last, not only in the inferior position
of the gill-clefts, but likewise in the small development of the prepalatine



True Saw Fishes.



SA W-FISH.



537



cartilages. The teeth of the saw are firmly implanted in distinct sockets of calcified
cartilage, while those in the jaws are minute and blunt. The wide spiracles are
situated behind the eyes ; the dorsal fins are without spines, the first being placed
above or near to the line of the base of the pelvic pair ; and the large caudal fin
may or may not have a distinct lower lobe. The saw consists internally of three,
or sometimes five, hollow calcified cartilages, in the form of long tapering tubes'
placed side by side, and held together by integument, which is likewise more or
less hardened by the deposition of calcareous matter. Several existing species of
the genus have been described, which are most abundant in the tropical seas, and




JAPANESE SAW-FISH



some of which are distinguished by the shape of the caudal fin, and the number of
pairs of teeth in the saw. These fishes not uncommonly grow to 20 feet in
length, but Day records one of 24 feet ; in such monsters the saw may be fully
6 feet in length, with a basal width of 1 foot. Some of the Indian species ascend
rivers to a considerable distance beyond the influence of the tides. . Saw-fishes use
their weapon of offence by striking sideways through the water, and thus inflict
terrific injuries, literally tearing to pieces the soft-parts of such animals as they
may strike ; and it is stated that in the Indian estuaries large ones have been
known to cut bathers completely in two. After tearing off pieces of flesh, or ripping
up the body of their victim with the saw, these fishes seize and swallow the smaller
fragments thus detached in their mouths. In the Malayan region the flesh of one



538 SHARKS AND RAYS.

of the species is highly esteemed as food ; and its tins, like those of sharks, are,
after due preparation, exported to China.

Fossil remains of extinct species of the genus occur throughout a large portion
of the Tertiary formations ; and an allied Eocene genus, Propristis, differs by the
circumstance that the teeth of the saw are not implanted in calcitied sockets. A
very remarkable type of saw-fish (Sclerorhynchiis) has left its remains in the
Cretaceous rocks of Syria. Not only does this fish differ from the living forms by
the distinctly depressed form of the relatively short and broad body, and the
backward extension of the pectoral fins, which almost reach the pelvic pair, but
the teeth, instead of being implanted in sockets, are merely attached to the skin by
an expanded and crimped base. Moreover, the central of the three rods in the
interior of the saw extends to the saw's extremity, instead of stopping short;
and it is not a little interesting to find that from the smaller teeth at the base of
the saw a complete gradation can be traced to the tubercles dotting the skin.
Assuming, as is most probably the case, that saw-fishes are nothing more than
highly specialised sharks, it is somewhat remarkable to find that the earliest known
member of the family has a somewhat skate-like form of body, and a type of
dentition which could not apparently be very readily modified into that of the
existing forms.

THE BEAKED RAYS, Family EHINOBATIVJE.

With this family we come to the first of what may properly be termed the
rays and skates, in all of which the pectoral fins are so extended forwards as to
join the head, and thus form, with the body, the so-called "disc"; the dorsal fins
being always situated on the tail, and the mouth being generally, and the gill-clefts
always, inferior. In the present family the tail is long and powerful, with two
well-developed dorsal fins, and a longitudinal fold on each side ; the disc is not
excessively dilated, the rayed portion of the pectoral fins stopping short of the
beak ; and there is no electric organ. Skates and rays in general are among the
most hideous and repulsive of all fish, some of them especially in the warmer
seas attaining enormous dimensions ; while some are dangerous from the wounds
inflicted by the spines of their tails. The tooth -like tubercles on the skin
frequently attain a great development, and are aggregated into prominent bosses
or longitudinal ridges. Dr. Giinther writes that the mode of life of these fishes is
quite in accordance with the form of their body, the true rays leading a sedentary
life, moving slowly on the bottom of the sea, and rarely ascending to the surface.
Their tail ha's almost entirely lost the function of an organ of locomotion, acting in
some merely as a rudder. They progress slowly by means of the pectoral fins, the
broad and thin margins of which are set in an undulating motion, entirely identical
with that of the dorsal and anal fins of the Pleuroiicct'xht'. Like the sharks, thry
are exclusively carnivorous, but being unable to pursue and catch rapidly moving
annuals, they feed chiefly on molluscs and crustaceans. The colour of their integu-
ments assimilates, however, so closely to that of their surroundings, that other fishes
approach near enough to be captured by them. The mouth of the rays being
entirely on the lower surface of the head, the prey is not directly seized by the



BEAKED RAYS. S3g

jaws; but the fish darts over its victim so as to cover and hold it down with its
body, when it is conveyed by some rapid motions to the mouth. Rays do not
descend to the same depth as sharks ; with one exception, none are known to have
been caught by a dredge working in more than one hundred fathoms. The majority
are coast-fishes, and have a comparatively limited geographical range, none extend-
ing from the northern into the southern temperate zone. Some of the eagle-rays
are, however, more or less pelagic, although when these ara met with swimming in
the open sea it is probable that shoal-water exists at no great distance. As may
be observed m many of the lochs on the west coast of Scotland, where these loath-
some creatures may be seen flapping lazily alone at the bottom of the clear water
skates and rays are more or less gregarious fishes. They frequently arrive suddenly
on oyster-beds -to the dismay of the owners -where they appear to remain so long




HALAVI KAY (i nat. size).

as any of the molluscs are obtainable. Writing of the species armed with caudal
spines, Day observes that they " lie concealed in the sand, and are reputed to be
able to suddenly encircle fish or other prey swimming above them with their long
whip-like tails, and then wound them with their serrated tail-spines." Many rays
ascend rivers to considerable distance, and some kinds, especially in Tropical
America, are exclusively inhabitants of fresh waters. Nearly all lay eggs.

To illustrate the typical genus, which is represented by about
a dozen species from the warmer seas, we take the halavi ray
(Rhinobatis halavi), which ranges from the Mediterranean and the coasts of Western
Africa to China. In these fish the depressed body passes imperceptibly into the
tail ; the muzzle is produced into a long beak, the space between which and the
pectoral fin is occupied by a membrane ; and the wide nostrils are oblique, with
their front valves separate. The blunt teeth are marked by an indistinct trans-



Typical Genus.



54 o SHARKS AND RAYS.

verse rido-e ; the dorsal fins, which are situated far behind the pelvic pair, have
no spines ; and the caudal has no lower lobe. Fossil species are found from the
Tertiary to the upper Jurassic. The allied Australian genus Trigonorhina differs
in having the front nasal valves united, and forming a broad quadrangular flap.




THOKNH.U-K SKATKS ( /,, iiat.



Rhynchobatis.



The third genus of the family, which is represented by two
species from the coasts of the tropical portions of the Indian Ocean,
differs in that the first dorsal fin is placed above the pelvic pair, in the presence
of a lower lobe to the caudal, and also in the form of the dental plate, which is



TRUE RAYS. 541

deeply undulated, so that the prominences of one jaw fit into hollows in the
opposite one ; the individual teeth being more or less diamond-shaped. These rays
do not exceed 8 feet in length. Several extinct genera occur in the upper
Jurassic strata of Europe




THE TRUE RAYS OR SKATES, Family

Represented by upwards of seven British species, all of which belong to the
typical genus, the true rays are characterised by the broad and rhombic form of
tin- disc, the skin of which is generally marked with tooth-like rugosities. The
tail has a longitudinal fold on each side, the degree of development of the median
fins is variable, and the rayed portion of the pectoral fins extends to the muzzle.
With the exception of occasional traces in the tail, electric organs are wanting.
Of the typical genus we take as a
well-known example the common
British thornback (Raia clavata),
of which two examples are shown
in the illustration. In this genus
the tail is very sharply defined
from the disc, which is generally
covered with rugosities ; the
pectoral fins stop short of the
extremity of the muzzle ; the
pel vies are deeply notched, with
a stout front cartilaginous ray;
the tail carries two dorsal fins,
mid the caudal is rudimentary, or
wanting. Most of these skates arc remarkable for presenting sexual differences,
which in the thornback and several other species display themselves in the dentition,
the teeth of the males being sharp and pointed, while those of the opposite sex
are blunt and flattened. Whereas the males of all the species are armed with patches
of claw-like spines lying in grooves on the upper surface of the pectoral fins, and
frequently also .on the sides of the head, the females of some species have a kind
of buckler of asperities on the disc, which is wanting in the other sex. In other
cases the variation takes the form of a difference in colour. The numerous
members of this genus are in the main characteristic of the cooler seas, and while
they are more abundant in the Northern than in the Southern Hemisphere, some
of them approach nearer to the Arctic and Antarctic Circles than is the case with
any other rays. The flesh of all of them is eatable, that of many species being
commonly sold as an article of food. The common skate (Raia batis), which is
ordinarily of from 2 to 4 feet in length, is greyish white in colour, with black
specks, the whole upper surface being more or less granulated. Buckland records
an unusually large specimen which weighed 90 Ibs. The thornback takes its name
from having the whole of the upper surface studded at intervals with the above-
mentioned claw-like spines ; the tail being also armed with longer spines, of which
a row runs along the middle of the back. The prevailing colour of the upper



JAWS OF MALE (A) AND FEMALE (B) THORNBACK SKATE.



542



SHARKS AND RAYS.



surface is brown, with numerous lighter spots, while beneath it is pure white.
Fossil skates of this genus range through the Tertiaries to the upper Cretaceous.
At the present day the family is represented by three genera, each with but few
species, from the warmer seas; and there are likewise certain extinct generic types.

THE ELECTRIC RAYS, Family TORPEDIXID.V.

In common with the electric eel, the members of this family are characterised
by their power of communicating galvanic shocks; the organs from which this




COMMON SKATE AND MARBLED ELECTRIC RAY (fa nat. size).

power is derived taking the form of a series of vertically-placed prisms, situated
on each side of the front of the disc between the head and the pectoral fins. In
addition to this distinctive feature, these rays are characterised by the broad and
smooth disc, in which the rays of the pectoral fins do not extend in advance of
the base of the muzzle, while the median fins are well developed. The family is



EAGLE-RAYS. 543

represented by several genera, ranging over the Mediterranean, Atlantic, and Indian
Ocean, into the distinctive features of which it will be unnecessary to enter here.
A well-known example of the typical genus is the marbled electric ray (Torpedo
nn/rmorata), represented in the lower figure of our illustration. The hexagonal
prisms forming the electric organs are subdivided into a series of cells by a number
of delicate transverse partitions; the cells at the two ends of the prisms being
in contact with the skin, and the whole structure liberally supplied with nerves.
Internally each cell is lined by a nucleated structure, within which is a mass of jelly-
like substance. "The fish," writes Dr. Gtinther, "gives the electric shock voluntarily,
when it is excited to do so in self-defence, or intends to stun or kill its prey; but to
receive the shock the object must complete the galvanic circuit by communicating
with the fish at two distinct points, either directly, or through the medium of
some conducting body. If an insulated frog's leg touches the fish, by the end of
the nerve only, 110 muscular contractions ensue on the discharge of the battery,
but a second point of contact immediately produces them. It is said that a painful
sensation may be produced by a discharge conveyed through the medium of a
stream of water. The electric currents created in these fishes exercise all the other
known properties of electricity; they render the needle magnetic, decompose
chemical compounds, and emit the spark." Specimens measuring from 2 to 3 feet
across the disc are stated to be able to disable a man by the discharge of the
battery. A writer in Land and Water, for 1869, in reply to Buckland, observes
that " I have taken two torpedos in the estuary of the Tees. You say the one you
dissected had nothing in its stomach. I was curious enough to see what those I
caught were living upon, so I put my knife into one, and took from him an eel
2 Ibs. in weight, and a flounder nearly 1 Ib. The next one I opened also, and was
astonished to find in him a salmon between 4 and 5 Ibs. weight; and what I was
more astonished at was that none of the fish had a blemish of any description,
showing that your idea of the fish killing his prey with his electrical force is
quite correct."

THE EAGLE-RAYS, Family MYLIOBATID^.

Known also by the ill-sounding title of devil-fishes, the eagle-rays include the
largest representatives of their tribe, and are characterised by the extreme width
of the disc, owing to the great development of the pectoral fins, which are, however,
interrupted at the sides of the head, to reappear as one or two small cephalic fins
on the muzzle. The tail is slender and whip-like, the cleft of the mouth straight,
and the teeth, when present, take the form of a solid pavement, adapted for
crushing the shells of molluscs, and other hard substances. The eagle-rays are
inhabitants of tropical and temperate seas ; and the members of some of the genera
are remarkable for the development of the so-called cephalic fins into a pair of
horn-like appendages, which are stated to be employed in capturing the prey and
helping to convey it to the mouth. Five genera are included in the family, all
the members of which appear to be viviparous.

The typical genus is represented by a small number of existing
Typical Genus. twQ of which are European ; one of these, Myliolatia aquila,



544 SHARKS AND RAYS.

occasionally visiting the British coasts, where it is often termed the whip-ray.
In this group the head is free from the disc, and the fin on the muzzle single.
The large, flat, hexagonal teeth form a tesselated pavement, highly convex in the
upper, but flat in the lower jaw; the individual teeth are arranged in seven
longitudinal rows, those of the unpaired middle row being much elongated and
transver.se, while the others form less irregular hexagons. The whip-like tail, in
addition to a dorsal fin near the root, is generally armed with a large barbed spine
about the middle of its length. In the young the middle row of teeth are not
larger than the lateral ones, and their relative width continues to increase
throughout life. The species above named, which has an almost cosmopolitan
distribution, may attain to a length of upwards of 15 feet, with a weight of about
800 Ibs. When captured, these rays lash out with their tails, and thus inflict
severe wounds with the spine. Fossil species of this genus occur through most of
the Tertiary strata ; and among these one from the Eocene of Egypt is remarkable
for its enormous size, the teeth of the middle row being rather more than 5 inches



Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 57 of 62)