SEA-SCORPIONS.
"And some rin up the hill and down dale, knapping the chucky
stanes to pieces wi' hammers like sae many road-makers run
daft. They say 'tis to see how the warld was made."--_St.
Ronan's Well._
Our first group of monsters is taken from a tribe of armed warriors
that lived in the seas of a very ancient period in the world's
history. Like the crabs and lobsters inhabiting the coasts of Britain,
they possessed a coat of armour, and jointed bodies, supplied with
limbs for crawling, swimming, or seizing their prey. They were giants
in their day, far eclipsing in size any of their relations that have
lived on to the present time. Some of them, such as the Pterygotus
(Fig. 1, p. 26), attained a length of nearly six feet. They belonged
to the humbler ranks of life, and, if now living, would without doubt
be assigned, by fishmongers ignorant of natural history, to that vague
category of "shell-fish" in which they include crabs, lobsters,
mussels, etc.
These lobster-like creatures, though claiming no relationship with the
higher ranks of animals, may well engage our attention, not only for
their great size, but also for their strange build.
[Illustration: Plate I.
SEA-SCORPIONS.
_Pterygotus anglicus._ _Eurypterus._ _Stylonurus._
Length 6 feet.]
There are no living creatures quite like them. Certainly they are not
true lobsters, and yet we may consider them to be first or second
cousins of those ten-footed crustaceans[4] of the present
day--lobsters, crabs, and shrimps, so welcome on the tables of both
rich and poor. Some naturalists say that their nearest relations at
the present day are the king-crabs inhabiting the China seas and the
east coast of North America; and there certainly are some points of
resemblance between them. Others say that they are related to
scorpions, and for this reason we call them Sea-scorpions. (See Plate
I.)
[4] Crustaceans are a class of jointed creatures (articulate animals),
possessing a hard shell or crust (Lat. _crusta_), which they cast
periodically. They all breathe by gills.
The first feature we notice in these creatures is the way in which
their bodies and limbs are divided into rings or joints. This fact
tells us that they belong to that great division of animals called
"Articulates," of which crabs, lobsters, spiders, centipedes, and
insects are examples. The celebrated Linnæus called them _all_
insects, because their bodies are in this way cut into divisions.[5]
But this arrangement has since been abandoned. However, they are all
built upon this simple plan, their bodies being like a series of
rings, to which are attached paired appendages or limbs, also composed
of rings, some longer and some shorter. Now, there must be something
very fitting and appropriate in this arrangement, for the creatures
that are thus built up are far more numerous than any other group of
animals. They must be particularly well qualified to fight the battle
of life; for like a victorious army they have taken the world by
storm, and still remain in possession. We find them everywhere--in
seas, rivers, and lakes; in fields and forests; in the soil, and in
all sorts of nooks and crannies; in the air, and even upon or inside
the bodies of other animals. Some of them, such as ants, bees, and
wasps, show an intelligence that is simply marvellous, and have
acquired social habits which excite our admiration.
[5] Lat. _in_, into, and _secta_, cut.
Articulate animals are a very ancient race, as well as a flourishing
one, for the oldest rocks containing undoubted fossils--namely,
certain slates found in Wales and the Lake District--tell us of a time
when shallow seas swarmed with little articulate animals known as
_trilobites_. They were in appearance something like wood-lice of the
present day; and the record of the rocks tells us plainly that
creatures built upon this plan have flourished ever since. We mention
this because they are related to the king-crabs of the present day,
and therefore to the huge old-fashioned sea-scorpions we are now
considering.
[Illustration: Fig. 1.--_Pterygotus anglicus._ (After Woodward.)
1. Upper side. 2. Under side.]
The best-known and largest of these creatures is represented in Fig.
1. It has received the name _Pterygotus_ (or wing-eared) from certain
fanciful resemblances pointed out by the quarrymen. It was first
discovered, along with others of its kind, by Hugh Miller, at Carmylie
in Forfarshire, in a certain part of the Old Red Sandstone (see Table
of Strata, Appendix I.) known as the Arbroath paving-stone. The
quarrymen, in the course of their work, came upon and dug out large
pieces of the fossilised remains of this creature. Its hard coat of
jointed armour bore on its surface curious wavy markings that
suggested to their minds the sculptured feathers on the wings of
cherubs--of all subjects of the chisel the most common. Hence they
christened these remains "Seraphim." They did not succeed in getting
complete specimens that could be pieced together; and the part to
which this fanciful name was given turned out to be part of the under
side below the mouth. It was composed of several large plates, two of
which are not unlike the wings of a cherub in shape. Hugh Miller says
in his classic work, _The Old Red Sandstone_--"the form altogether,
from its wing-like appearance, its feathery markings, and its angular
points, will suggest to the reader the origin of the name given it by
Forfarshire workmen."
A correct restoration, in proportion to the fragments found in the
Lower Old Red Sandstone, would give a creature measuring nearly six
feet in length, and more than a foot across. _Pterygotus anglicus_ may
therefore be justly considered a monster crustacean.
The illustrious Cuvier, who, in the eighteenth century founded the
science of comparative anatomy (see p. 5), astonished the scientific
world by his bold interpretations of fossil bones. From a few broken
fragments of bone he could restore the skeleton of an entire animal,
and determine its habits and mode of living. When other wise men were
unable to read the writing of Nature on the walls of her museum--in
the shape of fossil bones--he came forward, like a second Daniel, to
interpret the signs, and so instructed us how to restore the world's
lost creations. Hugh Miller submitted the fragments found at
Balruddery to the celebrated naturalist Agassiz, a pupil of Cuvier,
who had written a famous work on fossil fishes; and he says that he
was much struck with the skill displayed by him in piecing together
the fragments of the huge Pterygotus. "Agassiz glanced over the
collection. One specimen especially caught his attention--an elegantly
symmetrical one. His eye brightened as he contemplated it. 'I will
tell you,' he said, turning to the company--'I will tell you what
these are--the remains of a huge lobster.' He arranged the specimens
in the group before him with as much ease as I have seen a young girl
arranging the pieces of ivory in an Indian puzzle. There is a homage
due to supereminent genius, which Nature spontaneously pays when there
are no low feelings of jealousy or envy to interfere with her
operations; and the reader may well believe that it was willingly
rendered on this occasion to the genius of Agassiz." Agassiz himself,
previous to this, had considered such fragments as he had seen to be
the remains of fishes. As we have said before, this creature was _not_
a true lobster; but Agassiz, when he expressed the opinion just
quoted, was not far off the mark, and did great service in showing it
to be a crustacean. There were no lobsters or scorpions at that early
period of the world's history, and this creature, with its long
"jaw-feet" and powerful tail, was a near approach to a king-crab on
the one hand and scorpion on the other. If living now, it would no
doubt command a high price at Billingsgate; but, then, it would be a
dangerous thing to handle when alive, and might be more troublesome to
catch than our crabs or lobsters.
The front part of its body was entirely enveloped in a kind of shield,
called a carapace, bearing near the centre minute eyes, which probably
were useless, and at the corners two large compound eyes, made up of
numerous little lenses, such as we see in the eye of a dragon-fly.
This is clearly proved by certain well-preserved specimens. There are
five pairs of appendages, all attached under or near the head. Behind
the head follow thirteen rings, or segments, the last of which forms
the tail, two at least of these bore gills for breathing. All but two
of them, below the mouth, must have been beautifully articulated, so
as to allow them to move freely, as we see in the lobster of the
present day. But look at that lowest and largest pair of appendages,
the end joints of which are flattened out, and you will see that they
must have been a powerful oar-like apparatus for swimming forwards.
We can fancy this creature propelling itself much in the same way as a
"water-beetle" rows itself through the water in a pond. In all other
crustaceans the antennæ are used for feeling about, but in the
Pterygotus they are used as claws for seizing the prey.
In general external appearance, this huge Pterygotus greatly reminds
us of a tiny fresh-water crustacean, known as Cyclops--because it has
only one eye, like the giant in Homer's _Odyssey_. This little
creature, which is only 1/16 inch in length, is an inhabitant of
ponds. From its large eyes, powerful oar-like limbs, or appendages,
and from the general form of its body, Dr. Henry Woodward (the author
of a learned monograph on these creatures) concludes that the
Pterygotus was a very active animal; and the reader will easily gather
from its pair of antennæ, converted at their extremities into nippers,
and from the nature of its "jaw-feet," that the creature was a hungry
and predaceous monster, seizing everything eatable that came in its
way. The whole family to which it belongs--including Pterygotus,
Eurypterus, Slimonia, Stylonurus, and others--seems to have been
fitted for rather rapid motion, if we may judge from the long tapering
and well-articulated body. In two forms (Pterygotus and Slimonia) the
tail-flap probably served both as a powerful propeller, and as a
rudder for directing the creature's course; but others, such as
Eurypterus and Stylonurus, had long sword-like tails, which may have
assisted them to burrow into the sand, in the same way that king-crabs
do. Eurypterus remipes is shown in Fig. 2.
It has been stated above that our sea-scorpions are related to the
king-crabs. Now, this creature, it is well known, burrows into the mud
and sand at the bottom of the sea. This it does by shoving its broad
sharp-edged head-shield downwards, working rapidly at the same time
with its hinder feet, or appendages, and by pushing with the long
spike that forms a kind of tail. It will thus sink deeper and deeper
until nothing can be seen of its body, and only the eyes peep out of
the mud. It will crawl and wander about by night, but remains hidden
by day. Some of them are of large size, and occasionally measure two
feet in length. They possess six pairs of well-formed feet, the joints
of which, near the body, are armed with teeth and spines, and serve
the purpose of jaws, being used to masticate the food and force it
into the mouth, which is situated between them.
[Illustration: Fig. 2.--_Silurian merostomata._
1. _Stylonurus._ 2. _Eurypterus._ (After Woodward.)]
Now, this fact is of great importance; for it helps us to understand
the use of the four pairs of "jaw-feet" in our Sea-scorpions. What
curious animals they must have been, using the same limbs for walking,
holding their prey, and eating! Look at the broad plates at the base
of the oar-like limbs, or appendages, with their tooth-like edges.
These are the plates found by Hugh Miller's quarrymen, and compared by
them to the wings of seraphim. You will easily perceive that by a
backward and forward movement, they would perform the office of teeth
and jaws, while the long antennæ with their nippers--helped by the
other and smaller appendages--held the unfortunate victim in a
relentless grasp. And even these smaller limbs, you will see from the
figure, had their first joints, near the mouth, provided with toothed
edges like a saw.
With regard to the habits of Sea-scorpions, it would not be altogether
safe to conclude that, because in so many ways they resembled
king-crabs, they therefore had the same habit of burrowing into the
soft muddy or sandy bed of the sea, as some authorities have supposed.
Seeing that there is a difference of opinion on this subject, the
author consulted Dr. Woodward on the question, and he said he thought
it unlikely, seeing that, in some of them, such as the Pterygotus, the
eyes are placed on the margin of the head-shield; for it would hardly
care to rub its eyes with sand. Whether it chose at times to bury its
long body in the sand by a process of wriggling backwards, as certain
modern crustaceans do, we may consider to be an open question.
If only Sea-scorpions had not unfortunately died out, how interesting
it would be to watch them alive, and to see exactly what use they
would make of their long bodies, tail-flaps, and tail-spikes! Were
they nocturnal in their habits, wandering about by night, and taking
their rest by day? Such questions, we fear, can never be answered. But
their large eyes would have been able to collect a great deal of light
when the moon and stars feebly illumined the shallower waters of the
seas of Old Red Sandstone times; and so there is nothing to contradict
the idea.
Now, it is an interesting fact that young crabs, soon after they are
hatched, have long bodies somewhat similar to those of our
Sea-scorpions, with a head-shield under which are their jaw-feet, and
then a number of free body-rings without any appendages. These end in
a spiked tail. As the crab grows older, he ceases to be a
free-swimming animal--for which kind of life his long body is well
suited,--tucks up his long tail, and takes to crawling instead. Thus
his body is rendered more compact and handy for the life he is going
to lead. Lobsters, on the other hand, can swim gently forwards, or
dart rapidly backwards. Thus we see that the ten-footed crustaceans of
the present day are divided into two groups--the long-tailed and
free-swimming forms, such as lobsters, shrimps, and cray-fishes; and
the short-tailed crawling forms, namely, the crabs. Now, in the same
way, Pterygotus and its allies were long-tailed forms, while the
king-crabs are short-tailed forms. So were the trilobites of old.
Hence we learn that, ages and ages ago, before the days of crabs and
lobsters, there were long-tailed and short-tailed forms of
crustaceans, just as there are now, only they did not possess true
walking legs. They belonged to quite a different order, called
"thigh-mouthed" crustaceans, Merostomata, because their legs are all
placed near the mouth; and, as we have already learned, were used for
feeding as well as for purposes of locomotion.
Now, one of the many points of interest in Pterygotus and its allies
is that they somewhat resemble the crab in its young or larval state.
To a modern naturalist, this fact is important as showing that
crustacean forms of life have advanced since the days of the
sea-scorpions.
Their resemblance to land-scorpions is so close that, if it were not
for the important fact that scorpions breathe _air_ instead of
_water_, and for this purpose are provided with air-tubes (or trachea)
such as all insects have, they would certainly be removed bodily out
of the crustacean class, and put into that in which scorpions and
spiders are placed, viz. the Arachnida. But, in spite of this
important difference, there are some naturalists in favour of such a
change. It will thus be seen that our name Sea-scorpions is quite
permissible.
Hugh Miller described some curious little round bodies found with the
remains of the Pterygotus, which it was thought were the eggs of these
creatures!
Finally, these extinct crustaceans flourished in those ages of the
world's history known as the Silurian and the Old Red Sandstone
periods. As far as we know, they did not survive beyond the succeeding
period, known as the Carboniferous.[6]
[6] The student should consult Dr. Henry Woodward's valuable
_Monograph of the British Merostomata_ (Palæontographical Society), to
which the writer is much indebted. With regard to the representation
of _Pterygotus anglicus_ in Plate I., it has been pointed out by Dr.
Woodward that the creature was unable to bend its body into such a
position as is shown there. As in a modern lobster, or shrimp, there
were certain overlapping plates in the rings, or segments, of the
body, which prevented movement from side to side, and only allowed of
a vertical movement.