Copyright
Richard Lydekker.

The new natural history (Volume 5) online

. (page 54 of 62)
Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 54 of 62)
Font size
QR-code for this ebook


SALMON TRIBE.



53



nets." Dr. Guillemard adds that " every year the various kinds of salmon arrive
at the mouths of the Kamschatkan rivers with surprising regularity. The date of
the advent of these different species extends from May to mid- August ; but each
has its own time of arrival, which, from its constancy, appears to be more or less
independent of seasonal influences. A few fish apparently remain at or about the
river mouths during the summer, and eventually return to the sea, but these are so
few as to be scarcely worthy of mention. The vast majority practically all, in
fact ascend the streams to spawn, and, having once done so, die. In the case of
some species every fish appears to perish ; in others, a few get back to the sea."
The Oriental salmon (0. orientalis) of Kamschatka commonly grows to a weight of
from 50 to 60 Ibs. ; and the flesh is said to be superior in flavour to that of any
other member of the family.

The beautiful and delicately flavoured little fish known as smelts
are represented by three species, one of which (Osmerus eperlanus) is



Smelts.




COMMON SMELT (f liat. size).

an inhabitant of the seas and many fresh waters of Northern and Central Europe,
while the second (0. viridescens), which is perhaps only a variety, is confined to
the opposite side of the Atlantic, and the third (0. thaleichthys) is found on the
coasts of California. These fish form a kind of connecting link between the
salmon and its allies and the under-mentioned Coregonus, but internally differ
from both, the appendages to the intestine being short and few in number, and the
eggs small, while the teeth are strongly developed. The scales are of moderate
size ; the cleft of the mouth is wide, with the maxillary bone extending nearly or
quite to the hinder margin of the eye ; the teeth of the upper jaw are much smaller
than those of the lower; the vomer is armed with a transverse series of teeth,
several of which are tusk-like ; the palatines and pterygoids bear conical teeth ;



5 o 4 TUBE-BLADDERED GROUP.

\\hile there are also tusk-like teeth on the front of the tongue, and several
longitudinal series of small ones on the hinder part of the same. In length the
pectoral fins are medium. Growing to a length of 7 or 8 inches in the sea, the
common smelt is also found in rivers and landlocked lakes, where its size is always
considerably less. The allied candle-fish (Thaleichthys), of the Pacific coasts of
North America, distinguished by its rudimental teeth, has flesh of such an oily
nature that it can be burnt as a candle, although it is likewise used as food.

For want of a collective English name, we must allude by a
modification of their Latin title to an extensive group of mostly
fresh-water salmonoids, among which the powan (Coreyonus clupeoidcs), the
vendace (C. vandesius) of Lochmaben, and the pollan (C. pollan) oi the Irish lakes,
are well-known British forms. In these fish the scales are not strikingly large ;
the cleft of the mouth is of moderate size, with a broad maxilla, either short or of
medium length, and not extending beyond the front margin of the socket of the
eye ; while the teeth, if present at all, are minute and deciduous, in the adult
usually remaining only on the tongue. The dorsal fin is not over long, and
the caudal is deeply forked. Whereas in the small size of their eggs these fish
resemble the smelts, they differ in having about one hundred and fifty blind
appendages of nearly uniform length attached to the intestine. As already
mentioned, these fish differ from the typical salmonoids in the relations of the
bones on the top of the skull, on which account they are regarded by Professor
Cope as indicating a separate family. Represented by over forty species,
ranging over Northern Temperate Europe, Asia, and North America, core-
gonoids are for the most part entirely fresh-water fishes, although a few make
periodical migrations to the sea, while the European schnaspel (C. oxyrkynchux) is
as much a marine as a fresh- water fish. Local in their distribution in Europe,
although as many as three different species may inhabit the same lake, coregonoids
are extremely abundant in all the fresh waters of North America (where they are
commonly known by the name of white-fish) ; and whereas all the British forms
are small, some of the continental species may attain a length of fully two feet,
The genus may be divided into groups, according to the conformation of the muzzle
and jaws. Of these, the first is represented solely by the schnaepel (C. oxyrhi/ncli nx),
which frequents the coasts and rivers of Belgium, Holland, Germany, and Sweden,
and occasionally wanders into British waters. It is easily distinguished by the
production of the extremity of the upper jaw into a conical fleshy snout projecting
beyond the lower, while its scales are more or less nearly circular. In length, this
fish grows to a foot and a half. As an example of the group in which the muzzle is
obliquely truncated, with the nose projecting, we may take the marane (C.
lavaretuti), shown in the lower figure of our illustration; this fish being widely
distributed in the lakes of the Continent, where its flesh is highly esteemed as food.
Whereas in the Austrian lakes this fish does not exceed 14 or 15 inches in length,
with a weight of half a pound, in Lake Constance it grows to a couple of feet in
length, and from 4 to 6 Ibs. in weight. Living at great depths, this fish feeds
on worms, insects, and water-snails. While the powan belongs to another group
characterised by the vertical truncation of the muzzle, the pollan and vendace are
assigned to yet another division in which the lower jaw is longer than the upper,



SALMON TRIBE.



55



into a shallow notch of which it is fitted. As a representative of this latter group we
take the pigmy marane (G. albula) of Northern Europe, shown in the upper figure
of the illustration. Pollan, which grow to a length of about 6 inches, are largely
sold in Belfast during the spawning-season, at which time they come up from the
deep waters of Lough Neagh to the shallows. At times they occur in enormous
numbers, upwards of seventeen thousand having been taken on one occasion in the
early part of this century.




Grayling.



PIGMY MAKANE AND MAKANE (A Hat. size).

The last of the salmonoids that we have space to notice are the
grayling, of which the European species (ThymoMus vulgaris) is shown
in the upper figure of the illustration on p. 501. Nearly allied to the coregonoids,
the grayling are readily distinguished by the greater height and length of the
dorsal fin, which includes from thirteen to twenty-three rays. The cleft of the
mouth is also smaller, and the maxilla of small size. Small teeth are present
in the jawbones, as well as on the palatines and the head of the vomer, but they
are wanting on the tongue. The blind appendages of the intestine are less
numerous than in either the salmon or the coregonoids, and the air-bladder is
unusually large. The range of the genus includes a large portion of Europe,
Northern Asia, and the colder regions of North America. The common species is
found locally over a great part of Europe, ranging from Lapland to Venice, and
from England to Russia. It is, however, unknown in Ireland, and has only been
introduced of late years into Scotland ; while in England it is most abundant in
the rivers flowing from the limestone Pennine chain in the north, and the Red



5 o6 GANOIDS.

Sandstone districts of the central counties, and likewise in the chalk streams of the
south. In the latter area grayling occasionally run to nearly 4 Ibs. in weight,
but in Northern Scandinavia they may reach 1 Ib. more. In Switzerland they are
found in Lake Constance and other large pieces of water. An elegantly-shaped
fish, the grayling varies considerably in colour according to the season of the year,
the back being generally greenish brown, passing into grey on the sides, while the
under-parts are silvery. The sides of the head are yellow, with black spots, which
also occur on the fore-part of the body ; and brownish grey longitudinal stripes
run in the direction of the rows of scales. The pelvic and anal tins are violet,
frequently marked with brown crossbars ; the pectorals are yellow, turning to red
in the breeding-season ; while the black-bordered dorsal and caudal are generally
red, although sometimes blue; the former, and sometimes also the latter, being
ornamented with longitudinal dark bands or rows of spots. A second species,
with smaller scales, inhabit the mountain streams of Dalmatia, but the other two
are North American.

A remarkable fish from the fresh waters of the United States
known as Percopaia yuttata, which has the general characters of a
salmonoid but the mouth and scales of a perch-like type, is regarded as represent-
ing a family (Percopsidtv) by itself, nearly allied to the salmon tribe.

THE BONY PIKE AND ITS KINDRED, Suborder JEtheospondyli.

The remaining groups of the Teleostomous fishes exhibit a more or less decidedly
lower type of organisation than those described above ; and, although the sturgeons
are still well represented, these groups as a whole are evidently waning ones
at the present day, having only very few living forms, whereas in past epochs
some of them formed the dominant types in the fish-fauna of the world. The bony-
pikes of the fresh waters of North America constitute a family (Lepidosteidce)
which forms the sole existing representative of a distinct suborder. While
agreeing with the preceding suborders in the divisional characters mentioned
on p. 334, the members of this group and the next exhibit much more
marked differences from all the foregoing groups than do the latter from one
another. With the exception of the extinct spear -beaks, the tail is of the
abbreviated heterocercal type ; that is to say, that while its fin is more or less nearly
symmetrical, the vertebral column, which retains its primitive tapering extremity,
runs in the upper half. The scales are ganoid, and very frequently quadrangular,
although they may be rounded and distinctly overlapping. In the living represen-
tatives of both suborders the air-bladder is connected with the oesophagus by a
duct, in the same manner as in the tube-bladdered fishes; but the optic nerves
simply cross one another, without any interlacing of their fibres, and there is
a spiral valve to the intestine. Whereas, with the exception of one extinct
group of herrings, the whole of the suborders of bony fishes hitherto noticed are
unknown previous to the Cretaceous epoch, members of the two groups to
be now considered were abundant in the antecedent Jurassic period. The
group including the bony-pike may be distinguished from the next by the full
ossification of the internal skeleton ; the scales being always of the typical



BONY-PIKE.



57



quadrangular ganoid type, and the branchiostegal rays having no gular plate
in advance of them.

Existing Family. As a famil y> the bony-pikes, of which the common species
(Lcpidosteus osteus) is shown in our illustration, are distinguished
from all other fish by having the bodies of the vertebrae convex in front and con-
cave behind, instead of having both surfaces cupped. The fins are furnished with
fulcra, the dorsal and anal consisting of soft rays only, and placed far back, and
near the caudal, which is of the abbreviated heterocercal type ; while the trunk is
much longer than the abdominal portion of the vertebral column, and the bran-
chiostegal rays are comparatively few, and have not an enamelled outer surface.
In form, the body of the bony-pikes is elongate and subcylindrical ; the long
muzzle is either spatulate or beak-shaped : the cleft of the mouth wide ; and both




r BONY-PIKE (J nat. size).

the palate and jaws are armed with bands of rasp-like teeth, and also with larger
conical ones. There are four gills and three branchiostegal rays on each side ; and
the air-bladder is cellular. Bony-pike, of which there are three existing species,
are now confined to North and Central America and Cuba ; but they are repre-
sented in the European Eocene, and by allied extinct genera in the Eocene and
Miocene strata of the United States, one of these also occurring in the French
Eocene. The existing forms grow to a length of 6 feet, and are carnivorous, feed-
ing upon smaller fishes. They are often known by the name of gar-pike, although,
as mentioned on p. 400, that title is best restricted to a totally different group.

The extinct Jurassic spear-beaks (Aspidorhynchus) constitute a
second family (Aspidorhynchidce), distinguished by the normal
structure of the vertebrae, the homocercal tail, and the production of the upper
jaw ; the general form of the body and the arrangement of the fins being very
similar to that obtaining in the bony-pike.



Spear Beaks.



5 o8 GANOIDS.

THE Bow-Fix AND ITS ALLIES, Suborder Protospondyli.

The so-called bow-fin (Amia calva) of the fresh waters of the United States
is the sole existing representative of a second and larger subordinal group, differ-
ing from the last by the imperfect ossification of the skeleton, the notochord being
either persistent throughout life, or if more or less completely replaced by vertebra,
those in front of the caudal region have their bodies composed of three distinct
elements (pleurocentra and intercentrum), which remain separate and alternating
even when fully developed. The lower jaw is complex, and composed of several
pieces ; in the pectoral arch the infraclavicular plate is absent; and the pectoral fin has
more than three basal elements belonging to the true internal skeleton ; while the
tail is always abbreviated heteroeercal.




Existing Family.



THE BOW-PIN (J nat. size).

Together with three extinct genera, the bow-fin constitutes a
family (Amiidcv) characterised as follows. The lower jaw has its
suspending arrangement directed backwards, and the cleft of the mouth is wide ;
the degree of ossification of the vertebrae is variable, although these often form
complete discs ; the body is elongate or fusiform ; the margins of the jaws are
armed with an outer series of large and conical teeth, internally to which are
smaller ones; fulcra to the fins are either wanting or of minute si/e : and the
dorsal fin is of variable, although usually of considerable length. Having the scales
thin, somewhat rounded, and overlapping, the bow-fin represents a genus in which
there are no fulcra, and the long dorsal fin occupies three-fourths the length of the
body, while the anal fin is short, the caudal rounded, and the throat furnished with
a single gular plate, followed by a number of branchiostegal rays. The single
existing species of the genus, which attains a length of 2 feet, is confined to the
fresh waters of the United States, where it is exceedingly abundant in some of the



THE BOW-FIN.



59



Extinct Families.



northern lakes, but remains of extinct species have been obtained, not only from
the Eocene rocks of the same country, but likewise from the upper Eocene and
Miocene strata of Europe. Carnivorous in its diet, preying both upon other fish
and also upon aquatic crustaceans and insects, the bow-fin is capable of living for
fully an hour out of water ; and when in its native haunts, especially where the
water is foul, comes frequently to the surface to breathe, rising to the surface, and
taking in large mouthfuls of air without the emission of a single bubble. When
near the surface, this fish often utters a bell-like note, probabty due to the passage
of air from the air-bladder. The breeding-season, during which the colours of the
fish are more brilliant, lasts from May till the beginning of June. The bow-fins
breed among floating islands of herbage fringing the great lakes. Here they lay
thousands of minute eggs on the water-plants which form the base of a series of
tunnels, composed partly of root-fibres, and partly of a moss-like growth. Of the
nest thus formed, the male fish takes entire charge till the fry are hatched ; the
development of the eggs being unusually rapid. The embryos, while agreeing in
many respects with those of the typical ganoids, are stated to approximate in other
points to those of the higher bony fishes. Megalurus, from the upper Jurassic, is
an allied extinct genus with a short dorsal fin and fulcra; while the Jurassic
Eurycormus and Liodesmus likewise belong to the same family.

Among several
extinct families of
which the members are mostly
of Jurassic age, we may notice
the Pachycormidce, as represented
typically by Pachycormus, in
which, while the body and jaws
have the same form and structure
as in the bow-fish, the notochord

is persistent, and the ethmoid bone fused with the vomer to form a long beak ; the
fin-rays being slender and closely set, the dorsal fin short, and fulcra absent or
minute. Eugnathus and Caturus are well-known members of a third family
distinguished by the vertebrae being usually represented by incomplete rings, by the

large fulcra, and the short dorsal fin ; the caudal
fin being forked. The Pycnodonts, ranging from
the Lias to the Eocene, constitute another family
group, in which the body is either deeply fusiform
or rhomboidal ; the notochord has no ossification
around it ; the cleft of the mouth is narrow ; the
teeth are small, nodular, and aggregated into a
pavement, without vertical successors; the gill-
cover is of a very simple type; branchiostegal
rays and fulcra are alike absent ; and the dorsal
fin is elongated. The family is typically repre-
sented by the genus Pycnodus; but we have
figured as an example of the dentition the lower

RIGHT HALF OF THE LOWER JAW OF A , 7 -\r L Li C '1

PTCNODON-T (j/fon).-After Gaudry. jaw of the allied Mcsodon. Yet another family




SKELETON OF AN EXTINCT AMIOID (Caturus).




GANOIDS,



(Dapediidai) is represented by Dapedius, Lepidotus, and several other allied
genera, in which the body is more or less deeply fusiform, the suspensory apparatus
of the lower jaw either vertical or inclined forwards, the cleft of the mouth narrow,
the teeth cylindrical or in the form of button-like knobs, the vertebrae not more

than rings, and the
dorsal fin not ex-
tending more than
half the length of
the body. In this
family the teeth
have vertical suc-
cessors ; and while
some of the earlier
genera date from
the Trias, the scale-
tooths (Lepidotus), of which an example is figured in the illustration, survived till
the Chalk. Some of the species of this genus attained very large dimensions ; and
their remains are beautifully preserved in the Lithographic Limestone of Bavaria.
In all these the scales are of the typical quadrangular ganoid type.




THE GIANT SCALE-TOOTH, WITH A DETACHED SCALE AND TEETH

(much reduced).



THE STURGEON-TRIBE, Suborder Chondrostei.

This important suborder brings us to the last group of the fan-fmned fishes
(Actinopterygii), which forms a division by itself differing in several important
particulars from the one including the whole of the foregoing suborders ; the more
important characters of the first division having been given on p. 334. Whereas
in that division the number of dermal rays in the dorsal and anal fins is equal to
the supporting elements in the true internal skeleton, in the present division the
dermal rays are more numerous than their supports. Then, again, whereas in the
former division the pelvic fins have their superior row of supporting ossicles, or
baseosts, rudimental or wanting, in the present group these are well developed.
The living representatives of the sturgeon tribe agree with the bow-fish and its
allies in the want of any interlacing of the fibres of the optic nerves at their crossing,
and likewise in the presence of a spiral valve to the intestine. In both the living
and extinct types the tail is of either the diphycercal or heterocercal type. As a
suborder, the sturgeon tribe may be characterised by the more or less completely
persistent notochord, by the inferior and superior supporting ossicles (axonosts and
baseosts) of the dorsal and anal fins forming a simple and regular series, and also
by the presence of a pair of infraclavicular plates in the pectoral girdle. In all
the known forms there is a single dorsal and ana.1 fin, both of which are well
separated from the caudal; while in the existing members the air-bladder is fur-
nished with a duct. Although represented at the present solely by the sturgeons
and their allies, the group was very abundant during the Secondary epoch ; and
whereas the sturgeons, together with certain extinct families, form what may be
termed a degenerate specialised series characterised by the absence of ganoid scales
in a second and normal series the body was covered with such scales.



STURGEON TRIBE.



Toothed
Sturgeons.



1



The toothed sturgeons, of which there are two existing repre-
sentatives, each forming a genus by itself, constitute the family
Polyodontidce. While agreeing with the other members of the series in having
the cartilaginous skull invested with a series of superficial bony plates, these fishes
are specially distinguished by possessing a median unpaired series of bones in this
shield ; by the absence of branchiostegal rays ; the presence of minute teeth in the
adult ; the heterocercal tail ; and by the skin being either naked or with some scales
on the upper lobe of the tail. The first of the two existing genera is represented
by the spoon-beaked sturgeon (Polyodon folius) of the Mississippi, which grows to a

; length of 6 feet, and is characterised by the production of the upper jaw into a
very long spoon-like beak, with thin, flexible margins, equal to one-fourth the





SPOON-BEAKED STURGEON (^ nat. size).



total length in the adult, but still longer in the young. The gill-cover ends in a
I long tapering flap ; the upper lobe of the tail bears a numerous series of narrow
fulcra; and the air-bladder is cellular. On the other hand, the slender-beaked
sturgeon (Psephurus gladius) from the Yang-tse-kiang and Hoangho rivers of China,
differs in the more conical form of the beak, and in the large size and small number
of the caudal fulcra. Growing to an enormous length it is said as much as
20 feet this fish agrees with the preceding in the very small size of its eyes, from
which it may be inferred that both seek their prey without depending upon sight.
Indeed, in the muddy waters of the rivers they inhabit, eyes can be of little use,
and it has been suggested that these fish depend chiefly upon their beak, which is
probably employed as an organ of touch. The flesh of both species is eaten.
Among several fossil forms, w-e may mention the genus Crossopholis, of the North
American Eocene, on account of the retention of a series of oblique rows of scales

VOL. V. 33



5'4



GANOIDS.



on the upper lobe of the tail, as we thus have evidence of the descent of the family
from fully sealed fishes.

Toothless From the preceding family the typical sturgeons (Atipens&ridcB)

Sturgeons. ma y ^ e distinguished by the absence of teeth in the adult, and the

presence of five longitudinal rows of bony plates on the naked body, which is

elongate and subcylindrical in form, as well as by the presence of four barbels in a

transverse line on the under surface of the muzzle. The muzzle is somewhat

produced, and either subspatulate or conical in form, with the small, transverse

mouth on its lower surface. All the vertical fins are armed with a single series of

fulcra on their front edges ; the dorsal and anal are situated at a moderate distance

from the caudal ; and the large air-bladder is simple. Confined to the temperate

regions of the Northern Hemisphere, sturgeons are either exclusively or partially

fresh- water fish, some of them only ascending rivers for the purpose of spawning,

after which they return to the sea. With the slender-beaked .sturgeon, they

include the largest fresh-water fishes of this region, several of the species commonly

growing to 10 feet, while some are much larger. The females deposit enormous

numbers of extremely minute eggs, the product of a single individual having been

estimated at upwards of three millions during a season. This wonderful fecundity

easily accounts for the enormous numbers in which sturgeon, in spite of constant

persecution, still crowd the northern rivers during the spawning-season. Li

addition to the excellence of their flesh, sturgeon are valued for their roe, from

which is manufactured caviare, and for their air-bladder, the inner coat of which



Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 54 of 62)