creatures known mainly from their teeth and spines, for their skeletons
were of cartilage, and belonging to types that have mostly perished,
giving place to others better adapted to the changed conditions wrought
by time. Almost the only living relative of these early fishes is a
little shark, known as the Port Jackson Shark, living in Australian
waters. Like the old sharks, this one has a spine in front of his back
fins, and, like them, he fortunately has a mouthful of diversely shaped
teeth; fortunately, because through their aid we are enabled to form
some idea of the manner in which some of the teeth found scattered
through the rocks were arranged. For the teeth were not planted in
sockets, as they are in higher animals, but simply rested on the jaws,
from which they readily became detached when decomposition set in after
death. To complicate matters, the teeth in different parts of the jaws
were often so unlike one another that when found separately they would
hardly be suspected of having belonged to the same animal. Besides teeth
these fishes, for purposes of offence and defence, were usually armed
with spines, sometimes of considerable size and strength, and often
elaborately grooved and sculptured. As the soft parts perished the teeth
and spines were left to be scattered by waves and currents, a tooth
here, another there, and a spine somewhere else; so it has often
happened that, being found separately, two or three quite different
names have been given to one and the same animal. Now and then some
specimen comes to light that escaped the thousand and one accidents to
which such things were exposed, and that not only shows the teeth and
spines but the faint imprint of the body and fins as well. And from such
rare examples we learn just what teeth and spines go with one another,
and sometimes find that one fish has received names enough for an entire
school.
These ancient sharks were not the large and powerful fishes that we have
to-day--these came upon the scene later--but mostly fishes of small
size, and, as indicated by their spines, fitted quite as much for
defence as offence. Their rise was rapid, and in their turn they became
the masters of the world, spreading in great numbers through the waters
that covered the face of the earth; but their supremacy was of short
duration, for they declined in numbers even during the Carboniferous
Period, and later dwindled almost to extinction. And while sharks again
increased, they never reached their former abundance, and the species
that arose were swift, predatory forms, better fitted for the struggle
for existence.
_REFERENCES_
_The early fishes make but little show in a museum, both on account of
their small size and the conditions under which they have been
preserved. The Museum of Comparative Zooelogy has a large collection of
these ancient vertebrates, and there is a considerable number of fine
teeth and spines of Carboniferous sharks in the United States National
Museum._
_Hugh Miller's "The Old Red Sandstone" contains some charming
descriptions of his discoveries of Pterichthys and related forms, and
this book will ever remain a classic._
[Illustration: Fig. 5.--Pterichthys, the Wing Fish.]
III
IMPRESSIONS OF THE PAST
"_The weird palimpsest, old and vast,
Wherein thou hid'st the spectral past._"
The Rev. H. N. Hutchinson commences one of his interesting books with
Emerson's saying, "that Everything in nature is engaged in writing its
own history;" and, as this remark cannot be improved on, it may well
stand at the head of a chapter dealing with the footprints that the
creatures of yore left on the sands of the sea-shore, the mud of a
long-vanished lake bottom, or the shrunken bed of some water-course. Not
only have creatures that walked left a record of their progress, but the
worms that burrowed in the sand, the shell-fish that trailed over the
mud when the tide was low, the stranded crab as he scuttled back to the
sea--each and all left some mark to tell of their former presence. Even
the rain that fell and the very wind that blew sometimes recorded the
direction whence they came, and we may read in the rocks, also, accounts
of freshets sweeping down with turbid waters, and of long periods of
drouth, when the land was parched and lakes and rivers shrank beneath
the burning sun.
All these things have been told and retold; but, as there are many who
have not read Mr. Hutchinson's books and to whom Buckland is quite
unknown, it may be excusable to add something to what has already been
said in the first chapter of these impressions of the past.
The very earliest suggestion we have of the presence of animal life upon
this globe is in the form of certain long dark streaks below the
Cambrian of England, considered to be traces of the burrows of worms
that were filled with fine mud, and while this interpretation may be
wrong there is, on the other hand, no reason why it may not be correct.
Plant and animal life must have had very lowly beginnings, and it is not
at all probable that we shall find any trace of the simple and minute
forms with which they started,[2] though we should not be surprised at
finding hints of the presence of living creatures below the strata in
which their remains are actually known to occur.
[2] _Within the last few years what are believed to be indications of
bacteria have been described from carboniferous rocks. Naturally such
announcements must be accepted with great caution, for while there is no
reason why this may not be true, it is much more probable that definite
evidence of the effects of bacteria on plants should be found than that
these simple, single-celled organisms should themselves have been
detected._
Worm burrows, to be sure, are hardly footprints, but tracks are found in
Cambrian rocks just above the strata in which the supposed burrows
occur, and from that time onward there are tracks a-plenty, for they
have been made, wherever the conditions were favorable, ever since
animals began to walk. All that was needed was a medium in which
impressions could be made and so filled that there was imperfect
adhesion between mould and matrix. Thus we find them formed not only by
the sea-shore, in sands alternately dry and covered, but by the
river-side, in shallow water, or even on land where tracks might be left
in soft or moist earth into which wind-driven dust or sand might lodge,
or sand or mud be swept by the mimic flood caused by a thunder shower.
So there are tracks in strata of every age; at first those of
invertebrates: after the worm burrows the curious complicated trails of
animals believed to be akin to the king crab; broad, ribbed, ribbon-like
paths ascribed to trilobites; then faint scratches of insects, and the
shallow, palmed prints of salamanders, and the occasional slender sprawl
of a lizard; then footprints, big and little, of the horde of Dinosaurs
and, finally, miles above the Cambrian, marks of mammals. Sometimes,
like the tracks of salamanders and reptiles in the carboniferous rocks
of Pennsylvania and Kansas, these are all we have to tell of the
existence of air-breathing animals. Again, as with the iguanodon, the
foot to fit the track may be found in the same layer of rock, but this
is not often the case.
Although footprints in the rocks must often have been seen, they seem to
have attracted little or no notice from scientific men until about 1830
to 1835, when they were almost simultaneously described both in Europe
and America; even then, it was some time before they were generally
conceded to be actually the tracks of animals, but, like worm burrows
and trails, were looked upon as the impressions of sea-weeds.
The now famous tracks in the "brown stone" of the Connecticut Valley
seem to have first been seen by Pliny Moody in 1802, when he ploughed up
a specimen on his farm, showing small imprints, which later on were
popularly called the tracks of Noah's raven. The discovery passed
without remark until in 1835 the footprints came under the observation
of Dr. James Deane, who, in turn, called Professor Hitchcock's attention
to them. The latter at once began a systematic study of these
impressions, publishing his first account in 1836 and continuing his
researches for many years, in the course of which he brought together
the fine collection in Amherst College. At that time Dinosaurs were
practically unknown, and it is not to be wondered at that these
three-toed tracks, great and small, were almost universally believed to
be those of birds. So it is greatly to the credit of Dr. Deane, who also
studied these footprints, that he was led to suspect that they might
have been made by other animals. This suspicion was partly caused by the
occasional association of four and five-toed prints with the three-toed
impressions, and partly by the rare occurrence of imprints showing the
texture of the sole of the foot, which was quite different from that of
any known bird.
[Illustration: Fig. 6.--Where a Dinosaur Sat Down.]
In the light of our present knowledge we are able to read many things in
these tracks that were formerly more or less obscure, and to see in them
a complete verification of Dr. Deane's suspicion that they were not made
by birds. We see clearly that the long tracks called _Anomoepus_,
with their accompanying short fore feet, mark where some Dinosaur
squatted down to rest or progressed slowly on all-fours, as does the
kangaroo when feeding quietly;[3] and we interpret the curious
heart-shaped depression sometimes seen back of the feet, not as the mark
of a stubby tail, but as made by the ends of the slender pubes, bones
that help form the hip-joints. Then, too, the mark of the inner, or
short first, toe, is often very evident, although it was a long time
before the bones of this toe were actually found, and many of the
Dinosaurs now known to have four toes were supposed to have but three.
[3] _It is to be noted that a leaping kangaroo touches the ground
neither with his heel nor his tail, but that between jumps he rests
momentarily on his toes only; hence impressions made by any creature
that jumped like a kangaroo would be very short._
It seems strange, and it is strange, that while so many hundreds of
tracks should have been found in the limited area exposed to view, so
few bones have been found--our knowledge of the veritable animals that
made the tracks being a blank. A few examples have, it is true, been
found, but these are only a tithe of those known to have existed; while
of the great animals that strode along the shore, leaving tracks fifteen
inches long and a yard apart pressed deeply into the hard sand, not a
bone remains. The probability is that the strata containing their bones
lie out to sea, whither their bodies were carried by tides and currents,
and that we may never see more than the few fragments that were
scattered along the seaside.
That part of the Valley of the Connecticut wherein the footprints are
found seems to have been a long, narrow estuary running southward from
Turner's Falls, Mass., where the tracks are most abundant and most
clear. The topography was such that this estuary was subject to sudden
and great fluctuations of the water-level, large tracts of shore being
now left dry to bake in the sun, and again covered by turbid water which
deposited on the bottom a layer of mud. Over and over again this
happened, forming layer upon layer of what is now stone, sometimes the
lapse of time between the deposits being so short that the tracks of
the big Dinosaurs extend through several sheets of stone; while again
there was a period of drouth when the shore became so dry and firm as to
retain but a single shallow impression.
[Illustration: Fig. 7.--Footprints of Dinosaurs on the Brownstone of the
Connecticut Valley. _From a slab in the museum of Amherst College._]
Something of the wealth of animal life that roamed about this estuary
may be gathered from the number of different footprints recorded on the
sands, and these are so many and so varied that Professor Hitchcock in
two extensive reports enumerated over 150 species, representing various
groups of animals. One little point must, however, be borne in mind,
that mere size is no sure indication of differences in dealing with
reptiles, for these long-lived creatures grow almost continuously
throughout life, so that one animal even may have left his footprints
over and over in assorted sizes from one end of the valley to the other.
The slab shown in Fig. 7 is a remarkably fine example of these
Connecticut River footprints; it shows in relief forty-eight tracks of
the animal called Brontozoum sillimanium and six of a lesser species.
It was quarried near Middletown, in 1778, and for sixty years did duty
as a flagstone, fortunately with the face downwards. When taken up for
repairs the tracks were discovered, and later on the slab, which
measures three by five feet, was transferred to the museum of Amherst
College.
There is an interesting parallel between the history of footprints in
England and America, for they were noticed at about the same time, 1830,
in both countries; in each case the tracks were in rocks of Triassic
age, and, in both instances, the animals that made them have never been
found. In England, however, the tracks first found were those ascribed
to tortoises, though a little later Dinosaur footprints were discovered
in the same locality. Oddly enough these numerous tracks all run one
way, from west to east, as if the animals were migrating, or were
pursuing some well-known and customary route to their feeding grounds.
For some reason Triassic rocks are particularly rich in footprints; for
from strata of this same age in the Rhine Valley come those curious
examples so like the mark of a stubby hand that Dr. Kaup christened the
beast supposed to have made them _Cheirotherium_, beast with a hand,
suggesting that they had been made by some gigantic opossum. As the
tracks measure five by eight inches, it would have been rather a large
specimen, but the mammals had not then arisen, and it is generally
believed that the impressions were made by huge (for their kind)
salamander-like creatures, known as labyrinthodonts, whose remains are
found in the same strata.
Footprints may aid greatly in determining the attitude assumed by
extinct animals, and in this way they have been of great service in
furnishing proof that many of the Dinosaurs walked erect. The
impressions on the sands of the old Connecticut estuary may be said to
show this very plainly, but in England and Belgium is evidence still
more conclusive, in the shape of tracks ascribed to the Iguanodon. These
were made on soft soil into which the feet sank much more deeply than in
the Connecticut sands, and the casts made in the natural moulds show the
impression of toes very clearly. If the animals had walked flat-footed,
as we do, the prints of the toes would have been followed by a long heel
mark, but such is not the case; there are the sharply defined marks of
the toes and nothing more, showing plainly that the Iguanodons walked,
like birds, on the toes alone. More than this, had these Dinosaurs
dragged their tails there would have been a continuous furrow between
the footprints; but nothing of this sort is to be found; on the
contrary, a fine series of tracks, uncovered at Hastings, England, made
by several individuals and running for seventy-five feet, shows
footprints only. Hence it may be fairly concluded that these great
creatures carried their tails clear of the ground, as shown in the
picture of _Thespesius_, the weight of the tail counterbalancing that of
the body. Where crocodilians or some of the short-limbed Dinosaurs have
crept along there is, as we should expect, a continuous furrow between
the imprints of the feet. This is what footprints tell us when their
message is read aright; when improperly translated they only add to the
enormous bulk of our ignorance.
Some years ago we were treated to accounts of wonderful footprints in
the rock of the prison-yard at Carson City, Nev., which, according to
the papers, not only showed that men existed at a much earlier period
than the scientific supposed, but that they were men of giant stature.
This was clearly demonstrated by the footprints, for they were such as
_might_ have been made by huge moccasined feet, and this was all that
was necessary for the conclusion that they _were_ made by just such
feet. For it is a curious fact that the majority of mankind seem to
prefer any explanation other than the most simple and natural,
particularly in the case of fossils, and are always looking for a
primitive race of gigantic men.
Bones of the Mastodon and Mammoth have again and again been eagerly
accepted as those of giants; a salamander was brought forward as
evidence of the deluge (_homo diluvii testis_); ammonites and their
allies pose as fossil snakes, and the "petrified man" flourishes
perennially. However, in this case the prints were recognized by
naturalists as having most probably been made by some great ground
sloth, such as the Mylodon or Morotherium, these animals, though
belonging to a group whose headquarters were in Patagonia, having
extended their range as far north as Oregon. That the tracks seemed to
have been made by a biped, rather than a quadruped, was due to the fact
that the prints of the hind feet fell upon and obliterated the marks of
the fore. Still, a little observation showed that here and there prints
of the fore feet were to be seen, and on one spot were indications of a
struggle between two of the big beasts. The mud, or rather the stone
that had been mud, bears the imprints of opposing feet, one set deeper
at the toes, the other at the heels, as if one animal had pushed and the
other resisted. In the rock, too, are broad depressions bearing the
marks of coarse hair, where one creature had apparently sat on its
haunches in order to use its fore limbs to the best advantage. Other
footprints there are in this prison-yard; the great round "spoor" of the
mammoth, the hoofs of a deer, and the paws of a wolf(?), indicating that
hereabout was some pool where all these creatures came to drink. More
than this, we learn that when these prints were made, or shortly after,
a strong wind blew from the southeast, for on that face of the ridges
bounding the margin of each big footprint, we find sand that lodged
against the squeezed-up mud and stuck there to serve as a perpetual
record of the direction of the wind.
_REFERENCES_
_Almost every museum has some specimen of the Connecticut Valley
footprints, but the largest and finest collections are in the museums of
Amherst College, Mass., and Yale University, although, owing to lack of
room, only a few of the Yale specimens are on exhibition. The collection
at Amherst comprises most of the types described by Professor E.
Hitchcock in his "Ichnology of New England," a work in two fully
illustrated quarto volumes. Other footprints are described and figured
by Dr. J. Deane in "Ichnographs from the Sandstone of the Connecticut
River."_
[Illustration: Fig. 8.--The Track of a Three-toed Dinosaur.]
IV
RULERS OF THE ANCIENT SEAS
"_A time there was when the universe was darkness and water,
wherein certain animals of frightful and compound mien were
generated. There were serpents, and other creatures with the
mixed shapes of one another...._"--_The Archaic Genesis._
History shows us how in the past nation after nation has arisen,
increased in size and strength, extended its bounds and dominion until
it became the ruling power of the world, and then passed out of
existence, often so completely that nothing has remained save a few
mounds of dirt marking the graves of former cities. And so has it been
with the kingdoms of nature. Just as Greece, Carthage, and Rome were
successively the rulers of the sea in the days that we call old, so,
long before the advent of man, the seas were ruled by successive races
of creatures whose bones now lie scattered over the beds of the ancient
seas, even as the wrecks of galleys lie strewn over the bed of the
Mediterranean. For a time the armor-clad fishes held undisputed sway;
then their reign was ended by the coming of the sharks, who in their
turn gave way to the fish-lizards, the Ichthyosaurs and Plesiosaurs.
These, however, were rather local in their rule; but the next group of
reptiles to appear on the scene, the great marine reptiles called
Mosasaurs, practically extended their empire around the world, from New
Zealand to North America.
We properly call these reptiles great, for so they were; but there are
degrees of greatness, and there is a universal tendency to think of the
animals that have become extinct as much greater than those of the
present day, to magnify the reptile that we never saw as well as the
fish that "got away," and it may be safely said that the greatest of
animals will shrink before a two-foot rule. As a matter of fact, no
animals are known to have existed that were larger than the whales; and,
while there are now no reptiles that can compare in bulk with the
Dinosaurs, there were few Mosasaurs that exceeded in size a first-class
Crocodile. An occasional Mosasaur reaches a length of forty feet, but
such are rare indeed, and one even twenty-five feet long is a large
specimen,[4] while the great Mugger, or Man-eating Crocodile, grows, if
permitted, to a length of twenty-five or even thirty feet, and need not
be ashamed to match his bulk and jaws against those of most Mosasaurs.
[4] _It is surprising to find Professor Cope placing the length of the
Mosasaurs at 70, 80, or 100 feet, as there is not the slightest basis
for even the lowest of these figures. Professor Williston, the best
authority on the subject, states, in his volume on the "Cretaceous
Reptiles of Kansas," that there is not in existence any specimen of a
Mosasaur indicating a greater length than 45 feet._
The first of these sea-reptiles to be discovered has passed into
history, and now reposes in the Jardin des Plantes, Paris, after
changing hands two or three times, the original owner being dispossessed
of his treasure by the subtleties of law, while the next holder was
deprived of the specimen by main force. Thus the story is told by M.
Faujas St. Fond, as rendered into English, in Mantell's "Petrifactions
and their Teachings": "Some workmen, in blasting the rock in one of the
caverns of the interior of the mountain, perceived, to their
astonishment, the jaws of a large animal attached to the roof of the
chasm. The discovery was immediately made known to M. Hoffman, who
repaired to the spot, and for weeks presided over the arduous task of
separating the mass of stone containing these remains from the
surrounding rock. His labors were rewarded by the successful extrication
of the specimen, which he conveyed in triumph to his house. This
extraordinary discovery, however, soon became the subject of general
conversation, and excited so much interest that the canon of the
cathedral which stands on the mountain resolved to claim the fossil, in
right of being lord of the manor, and succeeded, after a long and
harassing lawsuit, in obtaining the precious relic. It remained for
years in his possession, and Hoffman died without regaining his
treasure. At length the French Revolution broke out, and the armies of
the Republic advanced to the gates of Maestricht. The town was
bombarded; but, at the suggestion of the committee of savans who
accompanied the French troops to select their share of the plunder, the
artillery was not suffered to play on that part of the city in which the
celebrated fossil was known to be preserved. In the meantime, the canon
of St. Peter's, shrewdly suspecting the reason why such peculiar favor
was shown to his residence, removed the specimen and concealed it in a
vault; but, when the city was taken, the French authorities compelled
him to give up his ill-gotten prize, which was immediately transmitted
to the Jardin des Plantes, at Paris, where it still forms one of the
most interesting objects in that magnificent collection." And there it
remains to this day.
[Illustration: Fig. 9.--A Great Sea Lizard, _Tylosaurus Dyspelor_. _From
a drawing by J. M. Gleeson._]