attention to the enormous correlative changes in other organs produced by
this case. Nearly the whole organism has been altered. The hard, firm
carapace has partly rendered the supporting functions of the vertebral
column unnecessary or impossible. In many tortoises, especially in the
large land-tortoises, the vertebrae and the capitular portions of the ribs
are reduced to mere bony outlines; the reduction to thin paper-like bony
lamellae proceeds with age. The iliac bones find a better support in the
costal plates; the contact with the sacral ribs is given up, and these ribs
fuse partly with the costal plates, or they are absorbed. The whole mass of
muscles of the trunk is completely lost in the region of the shell, but
traces of them exist in young specimens. Neck, limbs, and tail can in most
cases be withdrawn and hidden in the shell. When this is not possible it is
due to secondary changes. The neck is withdrawn either by being tucked away
{329}sideways (Pleurodira[129]), or by being bent in an S-shaped curve in a
vertical plane. In a left-sided profile-view of the animal, the head
represents the tail of the S. The neck is withdrawn by long muscles, which
are inserted into the ventral side of the middle of the neck, and extend in
the shape of vertical ribbons far back into the shell, arising from the
centra of some of the middle or even more posterior thoracic vertebrae.
Lastly, a few remarks on the PARTIAL REGENERATION, or the mending of
injuries to the shell. If part of the horny covering is badly bruised, torn
off, or rubbed through, or if part of the shell is crushed, the underlying
portion of the bony plate becomes necrotic, and the horny covering also
dies so far as its Malpighian layer is destroyed. Soon, however, the
uninjured Malpighian cells, around the margin of the wound, multiply, grow
into and beneath the injured portion of the bone, and form a new horny
layer, casting off the necrotic portion. After several months the
deficiency is patched up; new bone has grown in the deeper remaining strata
of the cutis, and the outside is covered by a continuous horny layer,
without, however, reproducing the original concentric moulding of the
shields. In badly crushed shells sometimes almost one-third of the whole
shell is thus cast off and mended within one or two years. The regeneration
of the forcibly stripped-off shields of _Chelone imbricata_ is described on
p. 386. Bitten-off tails and limbs, rather frequent occurrences in
water-tortoises, are of course not reproduced, but the wounds are healed
and covered again with scaly skin.
SENSE-ORGANS.–The EYE is by far the best developed sense-organ. It is
comparatively small. The pupil is round. The iris is mostly dark in
terrestrial forms, while in water-tortoises it is often brightly coloured,
for instance pale yellow in _Chelodina_, greenish and mottled with black,
pale grey, brown, etc., in various species of _Chrysemys_. _Cistudo_
presents a curious sexual dimorphism; the males have red, the females
brown, eyes. The sclerotic wall contains a ring of numerous small ossified
plates. There is no trace of a pecten. The eye is protected externally by
the two lids and the nictitating membrane. In some water-tortoises, notably
in _Chelodina_, the lower lid is transparent. Lacrymal and Harderian glands
are present.
{330}The SENSE OF HEARING is apparently not very acute, although tortoises
and turtles are frightened by noise, and can distinguish sounds; otherwise
they would have no voice, which is very tiny and piping in most tortoises
during the pairing season. In most water-tortoises the tympanic membrane is
thin and quite exposed; in land-tortoises it is often thick and covered by
the ordinary skin; lastly, in _Chelone_ the tympanic cavity is filled with
a plug of the much-thickened skin, possibly in adaptation to the
water-pressure when these creatures dive to considerable depths. The
ossicular chain is mostly reduced to a long, bony, columellar rod.
The SENSE OF SMELL is well developed. All Chelonians carefully smell their
food, in the air as well as under water. The individual predilection shown
by many species for different kinds of animal and vegetable food,–since
they are, for instance, able to distinguish between the various sorts of
cabbage, cauliflower, sprouts, etc.,–proves that they possess a
considerable amount of smell and taste.
Tortoises have a fine sense of touch; even the slightest tap on the shell
is noticed, and the skin of the soft parts is extremely sensitive. Tickling
of the sides of the tail, or of the hinder surface of a thigh, produces
ridiculous scratching actions of the same or of the opposite foot.
The DIGESTIVE APPARATUS is simple. Only a few peculiarities need be
mentioned. The tongue is mostly broad and soft; it cannot be protruded. The
oesophagus of the Chelonidae is covered with many conical projections
pointing towards the stomach. The latter is simple, except in _Sphargis_.
The intestine is devoid of a caecum, but the difference between the small
intestine and the rectum is very marked and often abrupt. The cloaca is
very roomy. It contains the large copulatory organ, which is unpaired,
grooved on its dorsal side, and is altogether constructed like that of the
Crocodilia. The large bladder opens ventrally into the urodaeum, a recess
of the cloaca; near its base open the urinary and genital ducts. Many
water-tortoises possess also a pair of lateral thin-walled sacs, the
so-called anal sacs, dorso-lateral diverticula of the walls of the
urodaeum. These sacs, which have highly vascularised walls, are incessantly
filled and emptied with water through the vent, and act as important
respiratory organs. When such a water-tortoise, for instance an _Emys_ or a
_Clemmys_, is suddenly taken out of the water, it squirts out a {331}stream
of this water, which is not, as is generally supposed, the urine from the
bladder.
The mode of RESPIRATION is interesting. The lungs are very complicated,
highly-developed, spongy structures. They are attached by their whole
dorsal surface to the inner lining of the shell. As they cannot expand
through their own initiative, and since the shell has made costal and
abdominal expansion impossible, the tortoise has to resort to other means
of producing the necessary vacuum. This is done partly by the neck and the
limbs, which act like pistons in being drawn in and out; partly by the
greatly developed hyoidean apparatus, by which, when the neck is stretched
out, the throat is alternately inflated and emptied, the air being
swallowed, or pumped into the lungs. Additional respiration, besides that
of the anal sacs mentioned above, is effected in various aquatic tortoises
by slightly vascularised recesses of the pharyngeal region. Most Chelonians
can exist for a very long time without breathing; sulky individuals remain
for hours or days under water. _Cistudo_ can shut itself up for an equally
long time. Nevertheless this and other land-tortoises easily get drowned.
All Chelonians lay white EGGS, round or oval, according to their kind, but
the shape of the eggs of one set sometimes varies within the greatest
limits. The shell varies from a parchment-like, flexible, scarcely
calcareous cover to a hard, well-polished case. As a rule the eggs,
imbedded in the ground, are hatched after a few months, but in some of the
northern kinds, e.g. _Emys orbicularis_, the hatching is deferred until the
next spring, the embryo's development being arrested during the winter. How
such eggs, buried a few inches only below the surface, withstand the often
very severe North German and Russian winter is a mystery. Whilst the
plastron is generally flat, it is more or less concave in the males of many
species, notably in _Testudo_, _Cistudo_, and _Emys_.
The general conclusions which can be drawn from the present GEOGRAPHICAL
DISTRIBUTION of the Chelonia are as few and unsatisfactory as those
applying to the Crocodilia, since all the main groups of Chelonians, and
many more extinct families, occurred together in bygone ages in the same
countries, for instance in Europe.
{332}[Illustration: FIG. 70.–Geographical distribution of Cryptodirous
tortoises.]
[Illustration: FIG. 71.–Geographical distribution of Pleurodirous
tortoises.]
The marine forms are naturally cosmopolitan, but the _Testudinidae_ are
likewise cosmopolitan, except in the Australian region. The _Chelydridae_,
now restricted to North and Central America, occurred formerly also in
Europe. The _Pleurodira_, in Mesozoic times plentiful in Europe, India, and
North America, are now restricted to South America, Australia, and Africa;
the _Pelomedusidae_ to Africa, Madagascar, and South America; the
_Chelydidae_ to South America and Australia. In the latter country all the
Chelonians belong to the Chelydidae. The _Trionychoidea_, occurring since
the Cretaceous epoch in North America, in Early and Mid-Tertiary times in
Europe, are now restricted to North America, Asia, and Africa. The country
richest in Chelonians is America; North and Central America together
possessing representatives of all the families except the Pleurodira, and
these we know to have died out there. The _Dermatemydidae_,
{333}_Cinosternidae_, and Chelydridae are now restricted to the Nearctic
sub-region (including Central America). Poorest in genera and species, all
of them Chelydidae, is the Australian region, where no fossils of other
families have yet been discovered. Europe, with its few Testudinidae, does
not come into consideration; Asia has at least Testudinidae and
Trionychidae, and in addition the solitary _Platysternum_ in Indo-China,
representative of a family whose affinities with the Chelydridae again
proclaim the validity of the Periarctic region.
[Illustration: FIG. 72.–Geographical distribution of Trionychidae and
Chelydidae.]
ORDER I. ATHECAE.
_The vertebrae and ribs are not fused with, but are free from, the
carapace, which consists of numerous small polygonal plates and is covered
with leathery skin without any epidermal shields. The limbs are transformed
into paddles. The neck is not retractile. Marine._
FAM. SPHARGIDAE.–_Sphargis_ s. _Dermatochelys coriacea_, the Leathery
Turtle or Luth, is the only recent species and is the largest of all recent
Chelonians. The biggest specimen in the national collection is about six
feet and a half long, from the nose to the end of the shell, which latter
is about four feet long; such a specimen may weigh half a ton. Agassiz,
however, says that he has seen some "weighing over a ton." The general
colour is dark brown, either uniform or with yellow spots. The Leathery
Turtle has a wide distribution, ranging over all the intertropical seas,
but it is rare everywhere; least so perhaps in the Western Atlantic from
Florida to Brazil and in the Indian Ocean.
{334}[Illustration: FIG. 73.–_Sphargis coriacea_, the "Leathery Turtle,"
young specimens, ventral and dorsal views. × 1.]
According to Agassiz it breeds regularly every year in the spring on the
Bahamas, on the Tortugas, and on the coast of Brazil, depositing its many
eggs on the sandy shore like other turtles. Accidentally it visits the
northern coast up to Long Island, and specimens, perhaps carried with the
Gulf Stream, have been caught on the coasts of Europe, for instance off
Dorsetshire. One was caught near Nantes in 1729, and is said to have made a
terrible noise when being killed. This is perhaps the reason why Merrem in
1820 invented the generic name _Sphargis_, supposed to be derived from
σφαραγέω (I make a noise). It has also been recorded from the
Mediterranean. It seems to be entirely carnivorous, living upon Molluscs,
Crustacea, and fish. The flesh is supposed to be unwholesome. It is a very
curious fact that of this rare species only large specimens, besides a very
few baby-turtles, are known or preserved in collections, while individuals
of intermediate size, say from four inches to three feet in length, have
never been recorded. If it were not for the fact that they are still known
to breed, it would look as if the {335}species were dying out. Perhaps they
are very shy, leading a pelagic life, diving at the least sign of danger,
and coming near the land only for the sake of breeding.
The structure of _Sphargis_ is so peculiar in many respects that it
deserves a somewhat full account. The neuro-central sutures persist on all
the vertebrae. The eight cervicals are short. All the ten trunk-vertebrae
carry ribs, and these, with the exception of the last, articulate between
the centra and with the neural arches; the first and tenth ribs are short,
the others are long and flattened, but not broad, with wide spaces between
them. The tail is short, although it consists of about twenty vertebrae;
these are devoid of chevrons.
The skull superficially resembles that of _Chelone_, chiefly owing to the
completely roofed-in temporal region. The supraoccipital crest is rather
short, covered completely by the parietals, the posterior margin of which
is rounded off instead of forming, as in the Chelonidae, a long projecting
triangular crest with the supra-occipital. The parietals are in broad
contact with the postfrontals, posteriorly they are just reached by the
squamosals. The quadrato-jugal is small, separated from the postfrontal by
the meeting of the squamosal with the jugal. The quadrate is notched
behind, and it separates the opisthotic from the squamosal. The
basisphenoid is large and broad, extending far forwards so as to separate
the pterygoids widely from each other except in their anterior portions,
which, instead of sending a lateral arm to the jugal and maxillary, as in
_Chelone_, are widely separated from these bones by the palatines. The
choanae lie on either side of the anterior half of the vomer, and are not
roofed over by ventral vomero-palatine wings.
The limbs and their girdles are essentially like those of the Chelonidae,
but are not derivable from them. The most remarkable feature is the shell.
The dorsal and ventral halves are directly continuous, forming one unbroken
case all round, which is composed of many hundreds of little bony plates,
irregularly polygonal, fitting closely into each other with their sutural
edges, and giving the shell a beautiful mosaic appearance. On the dorsal
side are a median row and three pairs of lateral rows of larger plates, and
these form seven longitudinal blunt ridges which all converge towards the
triangularly pointed tail-end of the shell. The ridges are not so much
produced by thickened {336}or spine-like edges of the plates, but by the
right and left halves of the plates being actually bent at an angle. This
is most conspicuous at the sides of the shell where it passes into the
ventral portion. The latter has two pairs of lateral and one median ridge.
The whole shell has consequently twelve ridges. The mosaic plates are
deeply imbedded in the cutis, being externally as well as internally
covered or lined with dense leathery skin. The epiderm is thin, and shows
no indications of horny scales. In young specimens the whole shell is soft
and very imperfectly ossified, later on it is quite rigid, although
comparatively thin. It is nowhere in contact with the internal skeleton,
except by a nuchal bone, which by a descending process articulates with the
neural arch of the eighth cervical vertebra.
The affinities of the Sphargidae and their position in the system are still
debatable. Whilst some authorities, _e.g._ Cope, Dollo, and Boulenger look
upon _Sphargis_ as the sole remnant of a primitive group in opposition to
all the other recent Chelonia, Baur considered it the most specialised
descendant of the Chelonidae. Dames agreed with him. Van Bemmelen has
modified this view in so far as he regards _Sphargis_ as the most
specialised Chelonian, but considers the differences between it and the
Chelonidae great enough to conclude that both Sphargidae and Chelonidae
represent two independent, partly parallel, branches which have arisen from
two different groups of terrestrial tortoises. Case,[130] from the study of
_Protostega_ and other fossil forms, tends towards Baur's view. He believes
that _Sphargis_ is the culminating form of a branch which through
_Psephophorus_ and with _Eosphargis_ has sprung from some creature like
_Lytoloma_, which at the same time is the starting-point of another branch
which culminates in the genera _Thalassochelys_ and _Chelone_, while lastly
a third branch contains _Protostega_, _Protosphargis_, and
_Pseudosphargis_. In other words, he considers them all Chelonidae. If he
is right we have of course no business to separate _Sphargis_ with its
fossil allies from the rest of the Chelonia as "Athecae."
However, Case has not proved his point. It is easy enough to understand
that the characters of the cranium and plastron of _Sphargis_ are in a
condition which by partial reduction can be derived from that of typical
Chelonidae. The structure of the {337}cervical vertebrae, the absence of
the marginal plates and the peculiar articulation of the nuchal with the
last cervical vertebra can be explained as convergent analogies, just like
the paddles of _Carettochelys_. But the shell of _Sphargis_ is
fundamentally different from and not homologous with that of the others.
Cope was therefore quite justified in distinguishing the Sphargidae as
"Athecae" in opposition to the others which Dollo later on, by contrast,
named "Thecophora." Unfortunate names, since both groups are undeniably in
possession of a θήκη or shell. Both authors meant, however, by Theca the
epidermal shields, but even this distinction is rendered invalid by
_Carettochelys_.
The most reasonable explanation has been suggested by Hay.[131] The mosaic
polygonal components of the shell of _Sphargis_ are, so to speak, an
earlier generation of osteodermal plates than the later generation of
longer and broader bony plates which in the Thecophora come into contact,
and fuse with, the neural arches and ribs. The osteoderms of _Sphargis_
belong to the same category as the dermal ossifications in the scutes of
Crocodilia, whilst the plates of the carapace and plastron of the
Thecophora belong to the category of the abdominal ribs. _Sphargis_ has the
first kind in its peculiar shell, the second kind in the deeper lying
plastron and in its nuchal plate. But it has lost, or perhaps had never
developed, the horny shields. The only difficulty is, however, the presence
of a plastron and of a typical neural plate in _Sphargis_. This difficulty
is not very serious. The plastron is a very old institution. It occurs
together with the more superficial osteoderms in _Caiman_, and the nuchal
plate may be the oldest of all dorsals. We can scarcely imagine that the
direct ancestors of _Sphargis_ had developed both kinds of shells, and that
comparatively recently the inner shell of the carapace was lost, leaving
only the nuchal plate. Fossils do not support such an assumption. Undoubted
ancestral forms of _Sphargis_ are very rare. _Psephophorus_ of the
Oligocene and Miocene of Europe had a continuous mosaic shell much
resembling that of _Sphargis_; _Eosphargis_ is represented by a
well-preserved skull from the London clay. Then follows a wide gap until we
come to _Psephoderma_ of the Rhaetic, or Upper Trias of Bavaria; the large
fragment of whose dorsal shell is composed of about 200 mosaic pieces. If
this fragment really formed part of the shell {338}of a Chelonian, its age
would speak greatly in favour of the Athecae being a very primitive and
independent group.
ORDER II. THECOPHORA.
_Thoracic vertebrae and ribs united with a series of median or neural and a
paired series of lateral or costal plates. Parietals prolonged downwards,
meeting the pterygoids directly or by interposition of an epipterygoid._
SUB-ORDER 1. CRYPTODIRA.–_The carapace is covered with horny shields. The
neck, if retractile, bends in an S-shaped curve in a vertical plane. The
pelvis is not fused with the shell._
FAM. 1. CHELYDRIDAE.–The plastron is small and cross-shaped (Fig. 61, 2,
p. 315); the bridge is very narrow, and the displaced abdominal shields are
widely separated from the marginals by a few irregularly shaped
inframarginals. The tail is long. The limbs, neck, and head are so stout
that they cannot be completely withdrawn into the shell. Snout with a
powerful hooked beak. American; only two genera, each with one species.
The temporal region is roofed very incompletely and only anteriorly by the
expanded parietals and postfrontals, which form a long suture. The plastron
consists of nine bony plates, a small entoplastron being present; there are
lacunae in the middle line, the plates meeting imperfectly, and the horny
abdominal shields are likewise separated by soft skin. The carapace has a
nuchal with long rib-like processes which underlie the marginals; the
neural plates form a continuous series. There are twenty-three marginal
plates. The pubic and ischiadic symphyses remain separate, enclosing one
large heart-shaped foramen. The five fingers and toes are webbed and are
protected by claws except the outer toe, the nail of which is usually
suppressed.
_Chelydra serpentina_, the Snapping Turtle, attains a large size, namely, a
shell-length of more than one foot, and a total length from the nose to the
tip of the tail of more than three feet. Its range extends from the
Canadian lakes east of the Rocky Mountains, through the United States and
Central America. The carapace of young specimens has three very marked
series of keels, which gradually disappear with age, until in very old
individuals the shell becomes quite smooth. The skin is very warty,
especially on the neck, and there is a pair of minute {339}barbels on the
chin. The tail carries three series of originally triangular horny crests,
which with age are transformed into blunt knobs. The general colour of this
rather ugly creature is olive, mottled with dark brown above and with
yellowish below.
According to Holbrook the Snapping Turtle is found in stagnant pools, or in
streams where the waters are of sluggish motion. Generally they prefer deep
water, and live at the bottom of rivers; at times, however, they approach
the surface, above which they elevate the tip of their pointed snout, all
other parts being concealed; and in this way they float slowly with the
current, but if disturbed they descend speedily to the bottom. They are
extremely voracious, feeding on fish, reptiles, or any animal substance
that falls in their way. They take the hook readily, whatever may be the
bait, though most attracted by pieces of fish; in this way many are caught
for the market. It is, however, necessary to have strong hooks and tackle,
otherwise they would be broken, for the animal puts forth great strength in
his struggles to escape, both with his firm jaws and by bringing his
anterior extremities across the line. When caught they always give out an
odour of musk, which in very old animals is sometimes disagreeably strong.
Occasionally the Snapping Turtle leaves the water, and is seen on the banks
of rivers or in meadows, even at a distance from its accustomed element. On
land his motions are awkward; he walks slowly, with his head, neck, and
long tail extended, elevating himself on his legs like the Alligator, which
at that time he greatly resembles in his motions; like the Alligator also,
after having walked a short distance, he falls down to rest for a few
moments, and then proceeds on his journey. In captivity they prefer dark
places, and are exceedingly ferocious; they will seize upon and bite
severely anything that is offered them, and their grasp upon the object
with their strong jaws is most tenacious.
The Snapping Turtles, or "Snappers," are feared on account of the ferocious
bites which they inflict, and they are hated because of the destruction of
valuable fish and water-fowl. They in turn atone for this damage by being
eaten, especially the younger half-grown individuals, the flesh of the
older ones being too much tainted with the odour of musk. The round eggs,
which are laid to the number of twenty to thirty in the summer {340}(in the
Northern States about June), are likewise good to eat. The first act of the
young creature on leaving the shell is said to be snapping and biting. In
captivity they are often very sulky, and refuse food stubbornly for many
months, perhaps for a whole year, and apparently without much harm to
themselves, since they lie quietly in the distant corner of the tank, now
and then slowly rising to the surface to breathe. Fresh-water algae grow on
the shell and in the mud which settles on it, and since this happens also
in the wild state, they are rendered as inconspicuous as old rotten logs.
In order to attract fishes they protrude a pair of worm-like, pale pink
filaments from the tip of the tongue.
[Illustration: FIG. 74.–_Macroclemmys temmincki_, "Alligator Turtle." × ⅙.]
_Macroclemmys temmincki_, the "Alligator Turtle."–In size and general
appearance much like the other Snapping Turtle, but the dorsal shields have
each a strong and prominent keel, and these three series increase in size
with age. The costal shields are separated from the marginals by an
additional series of about four supramarginals, well shown in the
illustration. The shields of {341}the cross-shaped plastron are subject to
much individual variation, small shields being frequently intercalated, or
rather retained, between the usual ones, especially between the pectorals
and abdominals, in the gular region, and on the narrow bridge, where the
inframarginals number one to three or even more. This species inhabits,
broadly speaking, the whole basin of the Mississippi and Missouri rivers.
This beast is as vicious as the other Snapping Turtle. According to Agassiz
it does not withdraw its head and limbs on the approach of danger, but
resorts to more active defence. It raises itself upon the legs and tail,
highest behind, opens the mouth widely, and throwing out the head quickly
as far as the long neck will allow, snaps the jaws forcibly upon the
assailant, at the same time throwing the body forward so powerfully as
often to come down to the ground when it has missed its object.
It lives mostly in the water, but makes considerable journeys overland.
Both in the water and on dry land the limbs move nearly perpendicularly,
and the body is raised high. On dry land a considerable part of the weight
of the body is borne by the long, strong tail.
"They are as ferocious as the wildest beast of prey, but the slowness of
their motions, their inability to repeat the attack immediately, their
awkwardness in attempting to recover their balance when they have missed
their object, their haggard look, and the hideous appearance of their
gaping mouth, constitute at such times a picture as ludicrous as it is
fearful and revolting. Their strength is truly wonderful. I have seen a
large specimen bite off a piece of a plank more than an inch thick. They
take hold of a stick with such tenacity that they may be carried for a
considerable distance suspended to it free above the ground. Fishes and
young ducks are their ordinary prey. They lay from twenty to forty or more
round eggs only about the size of a small walnut in holes which they dig in
sloping banks not far from the water" (Agassiz).
FAM. 2. DERMATEMYDIDAE.–The pectoral shields are widely separated from the
marginals by inframarginals, the gular shields are very small or absent,
and the tail is extremely short. Only two or three genera, with three or
four species in Central America.
The plastron is composed of nine plates. In _Dermatemys mawi_ it is large,
firmly joined to the carapace, covered with {342}eleven or more shields,
and there are four inframarginals; in _Staurotypus salvini_ of Mexico the
plastron is cruciform, with the anterior lobe movable, covered with seven
or more shields, according to the fusion of the anal shields and the
presence or absence of the gulars; there are only two inframarginals. The
pubic and ischiadic symphyses remain separate; the temporal fossa remains
widely open, the postfrontals scarcely touching the parietals. There are 23
marginal shields in _Staurotypus_, 25 in _Dermatemys_, including the
unpaired nuchal. The nuchal plate has a pair of rib-like processes like
those of the Chelydridae, but some of the posterior costal plates,
sometimes only one pair, meet in the middle line, overlying or suppressing
the corresponding neural plates. The shell of these aquatic tortoises is
rather flat, more or less keeled, especially in young specimens, and in the
fully adult condition is about one foot in length.
FAM. 3. CINOSTERNIDAE, represented by the single genus _Cinosternum_, with
about ten species in North and Central America, and one in Guiana. Closely
allied to the two previous families, with which it agrees by the separation
of the pubic and ischiadic symphyses, the presence of an ento-plastral
plate, the possession of inframarginal shields (Fig. 61, 3, p. 315), the
widely open temporal fossae, and the rib-like pair of processes to the
nuchal plate. It agrees with the Dermatemydidae in the interruption of the
neural plates by the meeting of several pairs of the costal plates. There
are 23 marginal shields; five or four shields, according to the presence or
absence of the gular on the plastron, and in some species these plastral
shields become, with age, more and more separated from each other by soft
skin (see Fig. 75). The shape and size of the plastron differ considerably
in the various species; in most of them, e.g. in _C. pennsylvanicum_ and
_C. leucostomum_, but not in _C. odoratum_, the anterior and posterior
lobes are movable, with transverse soft hinges, so that the animal can
completely close its shell. The skin of the legs and neck is so baggy and
loose that these parts slip in, the skin rolling off, when the creature
withdraws into its shell. They lay only a few–from three to five–elliptical
eggs, which have a shining, glazed, and thick, but very brittle shell.
{343}[Illustration: FIG. 75.–_Cinosternum odoratum_, young specimens. × ⅔.
A and B, males; C, female.]
_Cinosternum odoratum_, the Mud-Turtle, or Stinkpot Terrapin, so called on
account of the disagreeable smell which exudes from the inguinal glands.
The head is disproportionately large, with the snout rather compressed
laterally, and pointed underneath, with several short barbels. The neck is
long and slender. The carapace of the young is keeled, each of the neural
shields being raised in the middle line; but in full-grown specimens the
shell becomes quite smooth and rounded. The horny shields of the plastron
are relatively largest in the young, but they soon leave ever-increasing
spaces between them, which are then filled with soft skin only, which
thinly covers the underlying bone. The {344}fore- and hind-limbs,
especially the latter, are extensively webbed, and are provided with five
short claws. The general colour of the shell is horny brown, either uniform
or with darker spots or streaks. The neck and limbs are mottled brown. The
only ornamental colouring is a pair of clear yellow broad lines on each
side of the head, and a similar streak on each side of the lower jaw. On
the chin and upper throat are two pairs of small tentacles. The tail of the
male is of about the length of the hind-limbs, while that of the female is
so short that its tip scarcely reaches beyond the hinder margin of the
carapace. Length of the shell of full-grown specimens between four and five
inches. Very young specimens have a rather droll appearance, owing to the
long and slender neck with the large head, and the humpy back.
This species is common in the eastern half of North America, from Canada to
Texas. It is mainly aquatic, and is one of the dullest and shyest species.
My own specimens spend most of their time in the water, invariably in the
darkest corners, preferably under a stone or a log, and they do not leave
their hiding places until dark, in search of worms, meat, and all sorts of
animal food. For months I could never induce them to take food from a
stick, or even to eat in my presence, and it was not until after many weeks
that one of them at last protruded its head far enough to exhibit the
yellow stripes. When taken out of the water they draw in their heads, just
allowing the vicious little eyes to be visible, and opening the sharp-edged
mouth widely to bite deliberately and furiously at the unwary finger. Some
spent the winter in the water, in the greenhouses, feeding as usual, others
crept on land, hiding under moss, half buried in the soil, where they slept
for several months, but with interruptions in order to soak and to drink.
When spring is well advanced they prefer the water for their regular
sojourn. Some which had been sent over from New York arrived in a
deplorably dried-up condition, the skin being quite flabby and shrivelled,
but after a few hours' soaking they came round, and increased considerably
in weight, the limbs and neck becoming turgid.
_C. pennsylvanicum_ of Eastern North America has a larger, more oval
plastron. The head is not so strikingly large as in the other species and,
like the neck, is brown with yellowish spots, and often has streaks on the
sides. The tail of the male ends in a {345}nail-like horny point. The lobes
of the plastron are well hinged in the adult.
_C. leucostomum_ of Central America is larger, with a shell-length of six
inches. The plastron is not at all cruciform, but has a broad bridge, and
fills the box, moreover it has an anterior and a posterior hinge, so that
the box can be completely closed. Hence the vernacular name of the
Box-Terrapin.
FAM. 4. PLATYSTERNIDAE, represented by the single species _Platysternum
megacephalum_ in Burma, Siam, and Southern China.
The pectoral shields are widely separated from the marginals by
inframarginals, the plastron is large, oblong, not cruciform, and the tail
is long.
The plastron consists of nine plates, and is covered with six pairs of
shields, the most anterior of which are the broad gulars. The nuchal plate
has no rib-like processes. The neurals form a continuous series, and there
are twenty-three marginal scutes. The temporal fossae are completely roofed
over, owing to the long sutures formed by the parietals with the
postfrontals, moreover the postfrontals expand laterally so much that they
posteriorly come into broad contact with the quadrato-jugals and
squamosals, anteriorly with the maxillaries, so that the jugals are
completely surrounded by bones, and are shut off from the orbits and from
the temporal fossae. This is a unique arrangement, found nowhere else in
Tortoises. The pubic and ischiadic symphyses are connected with each other
by ligaments only.
The general appearance of this water-tortoise is rather curious, since the
carapace is much depressed, looking, especially in younger specimens, as if
it had been crushed in. The head, provided with very strong hooked jaws, is
strikingly heavy and large, and is covered above with one single large
shield. The tail is longer than the shell, which, in full-grown specimens,
reaches about six inches in length; it is, throughout its length, covered
with rings of squarish shields. A large specimen measures 14 inches in
total length, of which only five fall to the shell.
FAM. 5. TESTUDINIDAE.–The shell is always covered with well-developed horny
shields. Those which form the plastral bridge are in direct contact with
the marginals. The plastron is composed of nine bones. The digits have four
or five claws. The neck is completely retractile. The skull is devoid of
parieto-squamosal arches.
{346}This large family is cosmopolitan, with the exception of the
Australian and the adjoining Austro-Malayan countries. It contains genera
which form a continuous gradation between absolutely terrestrial and
thoroughly aquatic tortoises; and many are truly amphibious. As a general
rule the typically terrestrial kinds have a more curved or arched shell,
the digits are short, the eggs are more oval or round, and they are chiefly
herbivorous; the essentially aquatic kinds have a flatter or depressed
shell, webbed feet, with longer, often slender claws, the eggs are more
cylindrical, and they live on animal diet. About 20 genera, with more than
110 species, are recognised by Boulenger, but their essential characters
are nearly all internal, and therefore of no avail for the determination of
live or entire specimens.
_Chrysemys._–One of the most typical and widely distributed genera of
American Terrapins or water-tortoises. The carapace is flat; the plastron
is quite immovable, with a strongly developed bridge. Feet well webbed.
Tail short. Skull with a broad, complete, lateral, temporal arch. About one
dozen species, mostly in the eastern half of the United States, but the
whole genus ranges from Canada to Argentina.
Most of the young _Chrysemys_ are very pretty, the ground-colour of the
upper shields being green, variegated with yellowish-brown or blackish
markings, which often form exquisitely delicate patterns, either
concentrical (_Ch. concinna_, _Ch. rubriventris_), or more longitudinal
(_Ch. elegans_), or apparently quite irregular. The ground-colour of the
plastron is yellow, but the various species are best distinguished, at
least in very young individuals, by the arrangement of the dark brown spots
and patches. There are, for instance, several pairs of bold lateral and
several median patches in _Ch. rubriventris_; five pairs of ocellated spots
in _Ch. elegans_; only small median patches, where four plastral shields
meet, in _Ch. concinna_; while the plastron of _Ch. picta_ is uniformly
yellow.
These water-tortoises are very lively and shy, most so perhaps _Ch. picta_,
which is very quick and active. The food varies, often according to
individual fancy. Most of them eat fish. _Ch. picta_ is partial to insects,
but it also takes worms. Some of my specimens refused meat for a long time,
but ultimately they became so fond of it and of worms, that they came out
of the pond to take the food from the fingers; those in the Zoological
{347}Gardens of London have developed a taste for biscuits. One of my
largest _Ch. concinna_ fasted deliberately for eight months, refusing
worms, insects, meat, and frogs, only occasionally sniffing at the food,
until it was tempted with whitebait, which it took greedily. It refused,
however, smelts and pieces of soles, but after another month it
condescended to take meat regularly. Very young individuals live chiefly on
flies, which they watch for near the surface of the water; and they are
fond of smooth caterpillars, maggots, the larvae of humble-bees, and
similar soft creatures. They all spend most of their time in the water,
preferably floating near the surface, hidden between weeds; and they are
fond of basking. Some of them spend the night in the water, lying
motionless on the bottom, with heads and limbs turned in. Others prefer
hiding under moss. Those species, which, like _Ch. concinna_ and _Ch.
picta_, are common in the North, are of course perfectly hardy. For the
winter they dig themselves holes in the banks near the water, and they do
not come out again until the spring is well advanced. The eggs are
hard-shelled, mostly long and oval, and they are hatched before the end of
the summer. The larger species of Terrapin are eaten.
_Ch. picta_ (Fig. 76), the "Painted Terrapin," of the Eastern United
States, _e.g._ of New York and Long Island, is easily recognised by the
much depressed shell, which is absolutely smooth, and without a trace of a
keel. The colour above is dark olive-brown or blackish, with broad yellow
bands across the anterior ends of the neural and costal shields. Three or
four of these transverse bands are very conspicuous. The marginals are red,
with more or less concentric black and yellow markings. The pretty red
colour, with some black stripes, extends over the bridge, but the plastron
itself is uniformly yellow. The soft parts are likewise prettily marked,
the ground-colour is black-brown, with delicate bright yellow and red
stripes on the sides of the neck, limbs, and tail. The stripes are
originally yellow, but they develop an orange or red line in the middle, so
that each red stripe is ultimately narrowly edged with yellow; or the
yellow and red stripes alternate, for instance on the tail, which is short,
narrow, and pointed. The head is further adorned with a pair of conspicuous
bright yellow patches behind the eyes, and a smaller pair on the occiput.
The black and yellow stripes run across the gape of the mouth, some of the
lines even looking as if they had been {348}painted across. The nuchal
shield is elongated and very narrow, its anterior edge and that of the
neighbouring marginals are finely serrated. Very young individuals are at
once recognised by the prominent longitudinal median stripe of bright
orange extending over the nuchal and neural shields; the yellow transverse
bands are still absent; they appear when the longitudinal line vanishes.
[Illustration: FIG. 76.–_Chrysemys picta_, "Painted Terrapin." × ½.]
The "Painted Terrapin" is one of the few species of which, thanks to L.
Agassiz,[132] complete data of growth from the new born to old age are
known. During the first six or seven years the rate of growth is so uniform
that numerous specimens collected at the same time are readily arranged in
sets of the same age, simply by the differences they show in their size.
The successive lines of growth on the shields indicate the number of years.
After the seventh year the age is much more difficult to distinguish in
those tortoises, which, like _Ch. picta_, have a perfectly smooth
epidermis. This smoothness is due to the fact that the shields undergo a
process of moulting. An upper, quite {349}transparent layer of each shield
peels off completely like a piece of mica. I have been able to confirm
Agassiz' statement on _Ch. concinna_ in their third and fourth springs, and
on a number of adult _Ch. picta_. The latter were not allowed to hibernate,
being kept in a warm tank; they peeled completely during the late autumn,
and then the red and yellow colours underlying the newly formed shields
appeared very vividly; others moult at midsummer.
Growth of _Ch. picta_, after Agassiz.
+––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+
| Year. | Length of | Breadth of | Height of | Length of |
| | carapace. | carapace. | box. | tail. |
+––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+
| | millim. | millim. | millim. | millim. |
| Second | 26.5 | 25 | 12 | 16.5 |
| Third | 42 | 39.5 | 17 | 17.5 |
| Fourth | 51 | 49 | 21.5 | 20.5 |
| Fifth | 54 | 51 | 23.5 | 21.5 |
| Sixth | 59 | 56 | 25 | 23.5 |
| Seventh | 66 | 60 | 26.5 | 26 |
| Eighth (♂) | 72.5 | 61 | 28 | 27.5 |
| Ninth (♂) | 74 | 62 | 28 | 27.5 |
| Tenth (♂) | 77 | 64 | 30 | 28 |
| Eleventh (♂) | 80 | 67 | 30 | 28.5 |
| Fourteenth (♂) | 92 | 74.5 | 33 | 28.5 |
| Twenty-fifth (♀) | 121 | 92 | 43 | 34 |
| Old ♀ | 129 | 96 | 47 | 37 |
| Very old ♀ | 163 | 113 | 59 | 53 |
+––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+
The size of the eggs varies considerably, from 26 by 17 to 30 by 16
millimeters; sometimes they are perfectly round, 17 mm. in diameter.
_Ch. concinna._–The specific character by which this Terrapin may be easily
recognised is a pair of orange-red broad streaks, which extend from above
the eye to the sides of the neck. The general colour is olive-brown above,
variegated with yellowish dark-edged lines, which, together with numerous
rugosities, radiate from the middle field of each shield. The plastron is
yellow, often with blackish symmetrical patches, and sometimes these become
confluent and preponderant. Very young specimens are extremely pretty, the
ground-colour of the carapace being green, each shield with darker,
somewhat concentric markings, most conspicuous and regular on the upper
surface of the marginals, where the marks of the adjoining shields form one
pattern-system across the dividing lines. The plastron is either uniform
yellow or has a few pairs of blackish spots {350}which stand so closely
together that they form almost median patches.
The carapace is rough. The horny shields become very thin with age. The
anterior margin of the small nuchal and the neighbouring marginals is
faintly serrated. The posterior marginals form slight notches or
indentations between their edges. The plastron is almost square behind. The
edges of the jaws are nearly smooth, without hook and receiving-notch. The
tail is short.
[Illustration: FIG. 77.–_Chrysemys concinna_, in its third summer, × 1.]
[Illustration: FIG. 78.–_Chrysemys concinna_, in its third summer, × 1.]
This species inhabits the South-Eastern States of North America, from
Missouri and North Carolina to the Gulf of Mexico. Very large female
specimens have a shell sixteen inches in length. The eggs measure from 33
by 25 to 39 by 25 mm. or about 1½ inch in the long diameter.
_Emys._–The plastron is movably united to the carapace by ligament, and in
the adult has a slightly flexible hinge across the middle, between the hyo-
and hypo-plastral plates and the pectoral and abdominal shields. The
plastron is large, but does not quite close the box. Besides the small
nuchal there are twelve pairs {351}of marginal shields. The head is covered
with smooth skin; the temporal arch is complete. The limbs are extensively
webbed. The tail of the very young is nearly as long as the shell, but it
becomes relatively shorter with age, being reduced in the males to about
two-thirds, in the females to half the length of the shell. Only two
species are found in Europe, the other, _E. blandingi_, in Canada and
north-eastern U.S.A.
_E. orbicularis_ s. _europaea_ s. _lutaria_, the European
Pond-tortoise.–The shape and coloration of the shell change likewise much
with age. In the very young the shell is round, and the shields are rough
and slightly keeled, uniform dark brown above, black below, with a yellow
spot on each marginal and plastral shield. When half grown the dorsal
shields become quite smooth, and are striated or spotted, with yellow upon
a dark ground. The head, limbs, and tail are dark, with yellow or light
brown spots and small dots. In very old specimens all these yellow marks
disappear on the shell, which then becomes uniform brown or almost black.
The coloration is subject to much local and individual variation, and there
are two main types, the spotted and the radiate. It is difficult to say
which of the two is the prettier. One male which I caught in the Alemtejo
was very beautiful. The shell was almost black with a greenish shine when
in the water, and had many bright yellow and whitish spots. In the radiate
type the yellow is sometimes preponderant, so that each shield becomes a
study of delicately painted yellow, brown, and blackish lines radiating
from the centre. This variety seems to prevail in the south of Spain,
decidedly so in the Marismas, also in Northern Italy, whence most of the
European markets are supplied. The largest shell in the British Museum is
19 cm. = 7½ inches long. Fischer Sigwart received one from Naples which was
about 9 inches long, and this seems to have been kept as a pet, since its
shell had been gilt. Specimens about 5 inches in length may be considered
as fully adult. There are very few reliable observations on the growth of
individuals. One of F. Sigwart's grew in eleven years only about 2.5 cm. =
1 inch, when its shell was 13.4 cm. = 5¼ inches long–total weight of the
tortoise 491 grammes, about 1 lb. One of my own grew from 11 to 13.2 cm.
shell-length, and 8.3 to 10.6 cm. in width within eight years, but this was
one of the specimens which, living in a greenhouse, {352}did not hibernate.
This European pond-tortoise is now restricted to Southern and Middle
Europe, extending eastwards towards St. Petersburg and into Asia Minor,
southwards into Algeria. Formerly it had a much wider range, having been
found in post-glacial deposits in Southern Sweden, Denmark, the
Netherlands, and in East Anglia. Specimens have been found in the peat of
the fens of Norfolk and Cambridgeshire, contemporary with bones of the
Beaver, Roe-deer, and Pelican. The same applies to North Germany, where its
gradual disappearance from the western and central parts is obvious. Except
in Central France it is now practically unknown to the west of the Elbe
river. The country between the Elbe and Oder is now debatable ground,
_Emys_ being exceedingly rare. Some fifty years ago this seems to have been
different, to judge from the fact that farmers were rather fond of keeping
a tortoise in the water-troughs of the cattle to keep the water free from
worms and other impurities. Hence arose a silly superstitious custom. It
was considered equally conducive to the health of the pigs to keep a
tortoise in the foul tub into which all the dish-water and
kitchen-refuse–as potato-peels, sour milk, etc.,–were collected before the
mess was given to the pigs.
A specimen is still occasionally caught in the Havel and Spree rivers. I
myself have heard of one or two in the backwaters of the Oder near
Frankfurt, but they are vanishing, and it is difficult to say exactly why.
The universal lowering of the water-level owing to better drainage cannot
quite account for it, since there are thousands of suitable ponds, swamps,
and backwaters left. In Poland and in Eastern Prussia the tortoise is still
common.
This creature lives on a strictly animal diet. Worms, insects, frogs,
fishes form its main sustenance. Fishes are regularly stalked. The tortoise
watches its opportunity, slowly it half crawls, half swims along the
bottom, rises imperceptibly by a few gentle movements of the widely
spread-out webbed feet, then opens its sharp cutting jaws wide, and makes a
grab at the belly of the fish. Frogs are most easily stalked when they sit
upon a floating leaf. The tortoise rises from below, and often waits with
the nostrils and eyes just above the water and close to the frog. After a
while it sinks, and rises again, this time actually touching the toes of
the non-suspecting frog, smelling at them and deliberately biting with a
sideward turn of the head.
{353}[Illustration: FIG. 79.–_Emys orbicularis_, European Pond-tortoise
(left), and _Clemmys leprosa_, Iberian Water-tortoise (right). × ½.]
{354}What the jaws have got hold of is not allowed to escape again. The
tortoise holds on and tears the prey to pieces with the sharp-clawed
fingers. This takes a long time, only the scraped-off flesh and the
intestines being eaten. The skeleton remains and sinks to the bottom, while
in the case of a fish, the air-bladder floats away on the surface, and
remains there as one of the surest signs of the existence of tortoises in
that locality. The bones are cleaned with wonderful neatness. Some of my
grass-snakes shared this fate, their backbones, with the hundreds of pairs
of ribs, being picked or rather scraped clean, scarcely less well than if
they had been prepared for a museum.
As a rule the prey must be in motion to be seized, unless the tortoise has
watched it before, and even then the latter prefers to smell it before
biting. In captivity they soon learn to eat meat, and they become very
tame, but in their native haunts they are extremely shy and cautious. Fond
of basking upon a stone or on the banks, with the four limbs sprawling, or
with the hind-limbs stretched backwards, and with the webs spread out so as
to offer as large a surface as possible to the rays of the sun, they lie
motionless for hours and appear fast asleep. But the slightest noise, or
any other sign of our approach, is sufficient to send them plumping into
the water, and to make them scuttle along with unsuspected agility. Nothing
but the audible plump of the flat body and the widening rings of the
disturbed water indicate their presence. After a long time of waiting we
give it up, and turn away. That very instant we see a little ripple, caused
by the withdrawing of the tortoise, which had come to the surface and had
been watching us, with only the nose and eyes peeping out of the water, the
rest being concealed between the floating vegetation. Apparently they
cannot see us well with their eyes still under water, owing to the
difference of refraction, otherwise they would not peep out and then at
once turn back. It is certainly not for the want of air, since they can
remain below for many hours without breathing.
Although they generally feed in the water, they come on land when tame and
hungry enough to take the offered food. Sometimes they make long
migrations, perhaps because their old home is dried up or does not yield
food enough. They hibernate during the cold season, buried in the mud, and
they do not appear until {355}the spring is well advanced. During the
pairing season, on warm spring nights, they emit short piping sounds, and
when they have found each other, the couple swim about together. The white,
hard-shelled, long, oval eggs, averaging 25 to 15 mm., and about ten in
number, are laid on land. This is a very laborious and curious business.
The female having selected a suitable spot, not loose sand, but rather hard
soil free from grass and other dense vegetation, prepares the ground by
moistening it from the bladder and the anal water-sacs. Then it stiffens
the tail and bores a hole with it, moving the tail but not the body. The
hind-limbs then scoop out the hole, the broad feet moving alternately and
heaping up the soil on the side, until the hole is about five inches deep,
that is as far as the hind legs will reach. The eggs are laid at the bottom
in one layer, divided and distributed by the feet. Lastly, the soil is put
in again, and the tortoise, by repeatedly raising its body and falling
down, stamps the soil firm and flat, roughens the surface a little with its
claws, and leaves the nest to its fate. Nothing but an accident leads to
its discovery. The young are hatched, according to locality and the kind of
season, either in the same autumn or not until the next spring. Eggs laid
in a garden at Kieff, in Russia, were hatched eleven months later. This
implies hibernation of the embryo within the egg, and this is probably the
usual course of events, resembling the conditions of the development of
_Sphenodon_ (cf. p. 299). The pretty little creatures, scarcely larger than
a shilling-piece, are exceedingly difficult to rear. They require a tank
with green vegetation, stones to bask on and to hide under, and also dry
ground and moss for a change. They eat flies, tiny worms, tadpoles, etc.,
greedily enough, but for some occult reasons they do less well than many
another kind of water-tortoise. Miss Durham has, however, succeeded in
rearing one, which is now in its fourth year; the shell is 2 inches long,
and each shield shows three annual rings around the areola. This specimen
spent the winters in an unheated room under moss, not in the water.
_E. blandingi_, the North American species, has a more elongated and
decidedly higher carapace than its smaller European relation. The carapace
is dull black with many pale yellowish spots; the plastron is yellow, with
a large dark patch on the outer and hinder corner of each shield. The head
is dark brown above, bright {356}yellow below and on the throat, a contrast
which gives this tortoise a striking appearance. This species is extremely
voracious, becomes easily tame, and spends a great part of the day on land,
hiding under grass to avoid great heat, and withdrawing into the water for
the night.
_Clemmys._–The plastron is immovably united with the carapace, and is
devoid of any transverse hinge. The skull has a complete bony temporal
arch. This genus, consisting of eight species, is otherwise very much like
_Emys_, and is truly Periarctic.
[Illustration: FIG. 80.–Skull of _Clemmys leprosa_. × 3/2. _A_, dorsal
view; _B_, from the left side; _F_, frontal; _J_, jugal; _M_, maxillary;
_Par_, parietal; _Pr.f_, prefrontal; _Pt.f_, postfrontal; _Q_, quadrate;
_Qj_, quadrato-jugal; _Sq_, squamosal.]
_C. leprosa_ s. _sigris_ (Fig. 79).–The upper jaw has a median notch for
the reception of the upturned point of the lower jaw; the cutting edges of
the powerful beak are smooth. The shell is flat and long-oval, nowhere
serrated. The plastron does not quite fill the box. In the young the shell
is nearly round, and the horny shields form three series of keels, of which
the lateral pair disappear early; the shields are olive-brown, each with an
orange spot or streak; the plastron is dark brown, with a yellowish margin.
The adult looks very different. The shell has become much more oval, with
the greatest width behind the bridge. The long shields are smooth, and in
elderly specimens are without any trace of the original connective rings of
growth. The general colour of the shell is uniform pale olive-grey,
inclining to yellow on the plastron. The ground-colour of the soft parts is
olive-grey, but the sides of the head are adorned with orange-red or yellow
marks, the patch between the eye and ear and three or {357}four stripes on
the neck being especially conspicuous. The limbs have pale yellowish
streaks. All these markings are, however, subject to much individual
variation. While, for instance, the half-grown creatures are distinctly
agreeably coloured, often with a rich brown, nicely sculptured shell, and
with conspicuous orange and yellow marks on the skin, the very old ones
become rather ugly, the prevailing colour varying more and more into dull
uniform pale olive-grey.
The "Iberian Water-tortoise" is typical of the Iberian Peninsula, and
extends through Morocco and Algeria far into North-Western Africa. Unknown
to the north of the Cantabrian range, decidedly scarcer than its cousin
_Emys_ in the northern half of the Peninsula, it becomes common in the
south. In the Alemtejo, in the lower parts of Andalucia and in Morocco,
there is scarcely a pool, stream, or river in which it is not found,
feeding on any living thing it can master, although fishes and frogs are
its principal prey. When the streams and watercourses run dry, during the
hot and dry season, the tortoises crowd together into the remaining pools,
which soon become stagnant and filthy. But even these havens of refuge are
not of lasting avail. They are soon cleared of anything edible, and the
stinking water becomes dirtier and hotter day by day. Ultimately the
tortoises leave the pool to hide under ledges of rocks, where they
aestivate for months. This life in the muddy, slimy pools renders these
tortoises peculiarly liable to the attacks of a certain fresh-water alga,
which enters through the cracks in the horny shields and then flourishes in
the Malpighian layer, and even in the underlying bone itself. This becomes
gangrenous in patches, and the whole shell assumes a leprous appearance,
hence the specific name of _leprosa_. Everything combines in favour of this
destructive little alga. The tortoise, covered with mud, basks in the hot
sun, the horny shields become brittle and crack, often peeling off in thin
flakes. But those happy individuals which inhabit permanent rivers, or
pools which do not dry up, are, and remain, as clean as other
water-tortoises.
_C. leprosa_ has a most disagreeable, offensive smell, something like
concentrated essence of fish, due to the secretion of a pair of large
glands situated beneath the skin of the inguinal region, and opening behind
the bridge. Freshly caught specimens stink horribly, but when they have
become accustomed to being {358}handled, they no longer void these glands.
They always withdraw into the water for the night, and the cold season is
spent in the mud. Their time of propagation is still somewhat doubtful.
Very young tortoises are met with in the Peninsula in March, when they are
already in the rivers. Those which I imported in the summer and autumn
invariably dug their nests and laid their long, oval eggs (28 to 33 mm.
long) in the month of November, pairing having taken place some two or
three months previously. The mode of making the nest is exactly the same as
that described for _Emys_. As most of my specimens were kept in a
greenhouse with a permanent current of warm water through their tanks, they
never hibernated, nor did they pass through a torpid time in the summer,
but they showed an irresistible love for the hot-water pipes, huddling
together by the dozen, so that the pipes had to be screened off to prevent
the creatures from getting burnt. Until this precaution was taken, they
heated themselves so much that the shields and even the bones of the
plastron were injured. The artificial warm temperature and the complete
suppression of seasonal rest had no bad influence, most of the tortoises
living with undiminished appetite for more than twelve years, but the
sexual period became disturbed, pairing occurring ultimately at all times
of the year. The eagerness of the males, however, had a peculiar evil
secondary influence upon the females. The male tries to fasten on to its
mate by biting into the collar-like fold of the neck into which the head is
withdrawn, and this repeated irritation produces sores and swellings, which
latter in their turn prevent the female from wiping the eyes with the back
of the fore-limbs, a habit common to most, if not all, tortoises.
Ultimately the eyes fester, and the tortoise, becoming practically blind,
falls off its feed, leaves the water, which makes matters worse, and is
very difficult to cure.
In other respects they are very hardy, and they stand acclimatisation in
England perfectly. Some, thriving in a deep concreted pond, passed through
the very severe winters of several years ago, hiding in the mud below the
ice, and appeared in the spring in perfect health. They can also
successfully pass the winter under moss and a heap of loose garden-rubbish.
_C. caspica_ is closely allied to _C. leprosa_, which it represents in the
Balkan Peninsula and in Asia Minor. It differs from the south-western
species chiefly by having the cutting edges of the {359}upper jaw finely
denticulated, and by its prettier coloration, each shield being ornamented
with yellowish streaks which form a kind of ∞ on the costals, and a ring on
the marginals. The plastron is black in the young, with yellow and black
patches in the adult. The head and sides of the neck are striped with
yellow lines, narrowly edged with black, and the rest of the soft parts is
marbled dark olive and yellow. A few other species occur in China, Japan,
and North America.
_Clemmys insculpta_, one of the American species, ranging from Maine to
Pennsylvania and New Jersey, is easily recognised by the peculiar
reddish-brown and brick-dust colour of the soft parts. The strongly keeled,
posteriorly emarginate carapace is reddish brown, with radiating yellow
lines. Each shield is delicately sculptured. The plastron, which is notched
behind, is yellow, with a large black patch on the outer corner of each
shield. Length of a full-grown specimen 8 inches. They frequent the rivers
and ponds, but are also very fond of leaving the water, sometimes remaining
for months in dry places.
_Malacoclemmys_ of North America, with three species only, is closely
allied to _Clemmys_, from which it differs chiefly by the very broad
alveolar surface of the upper jaw, and by the more forward position of the
entoplastron, this being placed anteriorly to the humero-pectoral suture.
We mention this genus since one of its species, _M. terrapin_, is so
extensively eaten in the Eastern United States. The shell is oval, slightly
emarginate behind, obtusely carinated along the middle line. The upper
parts of the shell are brown or greenish, with dark concentric lines; the
marginals are yellow below, each with a ring of dark grey, and forming a
peculiarly up-turned rim. The plastron is yellowish, either with concentric
stripes and dusky lines or uniform yellow. But it is the colour of the soft
parts which gives this otherwise dull-looking creature its delicately
pretty appearance. The skin is, namely, greenish white with countless small
black dots. The males remain much smaller than the females, and have the
concentric stripes more pronounced. This species, the choicest of the
edible Terrapins, frequents the salt marshes of the east coast of North
America, from Rhode Island to the Gulf of Mexico, being most abundant
around Charleston.
The following is a condensed account of an article which appeared in the
New York Sun, 18th September 1898, the data {360}of which were supplied by
the manager of the terrapin-farm at Beaulieu, Georgia. The continued
hunting and the unfailing demand for them are making them very scarce, so
that enterprising men have established terrapin-farms or "crawls" for the
keeping and breeding of terrapins. The "crawls" in question are near the
river. The larger is 310 by 60 feet, and is divided into three compartments
for three sizes. The smaller "crawl" is for the babies, and is 100 by 8
feet. Through both "crawls" runs a ditch connected with the river and
making a circuit of the farm. The bottom of the "crawls" is on a level with
the low tide, and is covered with a layer of mud about six inches deep.
Into this the terrapins burrow in the winter. The average population of
terrapins is about 40,000, one half "bulls" and the other half "heifers."
The latter are much better eating, and grow to a much larger size, namely,
eight inches on the plastron, while the "bulls" rarely grow over five
inches long. When a female reaches six to eight inches it is called a
"count." Those between five-and-a-half to six inches long are known as
"two-for-threes," while those from five to five-and-a-half inches are known
as "halves." They are fed exclusively on shrimps and crabs on account of
the flavour, although they will eat almost anything. The 40,000 consume on
an average twenty bushels of crustaceans a day. They are quite indifferent
to cold. The manager saw some placed in a block of ice and frozen fast to
it; after four or five days they were chopped out, thawed, and were soon as
lively as ever. The statement that it takes these terrapins only seven
years to attain full commercial growth is surprising, and is probably an
underestimate. At the end of the large "crawl" is a board to enable the
females to creep into a sand-pit, where they lay the eggs from April to
June, eight to twelve forming a set. It is necessary to get the babies away
from their parents as soon as they hatch, else they will be eaten. The
young must not be exposed to the cold. The old ones have a large amount of
curiosity. The best way of catching them is for two men to go out in a boat
with a net. They row carefully along until they come to a likely spot. Then
one man raps several times sharply on the boat with a stick, and if there
are any terrapin about they will come to the surface just as fast as they
can get there to see what is going on, and the other man scoops them up
with a little net. Another {361}way, used in the salt marshes, is for the
negroes to go tramping through the mud and water. If they pass any terrapin
these will rise out of the mud to see what the disturbance is. The captives
are then fattened in the "crawl." When the men go in to feed them they
whistle, and terrapin from all over the "crawl," thousands of them, come
swimming through the water, piling over each other in their efforts to get
close to the man with the shrimps and crabs.
_Cistudo._–The plastron, without forming a bridge, is connected with the
carapace by ligaments, and is divided into two movable lobes, the
transverse hinge being so perfect that the box can be completely closed
after head, legs, and tail have been withdrawn. The nuchal shield is very
small; the first four neurals are large and broad, the fifth much broader
than long. There are twelve pairs of marginal shields. The carapace is high
and arched. The digits are almost completely free. The tail is very short.
The skull is without a bony temporal arch, the quadrato-jugal and the jugal
being absent. Only two species, in North America.
_C. carolina_ of the Eastern United States is a very interesting species.
Closely allied by its internal structure to the water-tortoises, it has
become absolutely terrestrial; and the shape of the head, the convex shell
which is coloured black and yellow or orange-brown, and the short webless
fingers are all terrestrial features. But the rather long toes, provided
with long and sharp claws, the broad and flat feet, enlarged by a broad
fold of skin on the outer margin, the long oval eggs, the smooth covering
of the head, and the preponderant animal diet, still proclaim the aquatic
relationship of this tortoise. It is in fact a genus which has changed
habits and features from aquatic to terrestrial life. The head is covered
with a smooth skin, and the upper beak, especially in old specimens, is
strongly and broadly hooked. The eyes of the males are red, those of the
females are brown. The plastron of the males is concave, that of the
females is flat. Large females reach a length of nearly six inches. The
young are nearly round, with high, arched back and prominent keels. The
keels of the middle line remain a long time, but they gradually flatten
down with age, being prominent only at their posterior ends. Each dorsal
shield is originally nicely sculptured, with a well-marked areola and
concentric rings. Very old individuals {362}become much flatter on the top
of the shell, but the sides remain steep, so that the whole shell roughly
resembles a somewhat oblong box with the corners rounded off, and the whole
upper surface rubbed down quite smooth. The variations of colour are almost
endless, and they occur in the same localities. I have a number of all ages
from Long Island, near New York. The half-grown are beautifully reddish or
orange-brown with dark patches, median keels prominent, plastron uniform
black-brown. In others the dark-brown prevails over the lighter markings,
which are yellower and more spotted or dotted than patched. Some of the
oldest, with quite smooth shells, are black, with small, round, light
yellow spots. Others are vermiculated or striped with yellow and black. The
soft parts vary to the same extent, some showing on the neck a beautiful
intricate pattern of yellow, reddish and brown, while in others these
colours are arranged more or less in longitudinal stripes.
These "Box-tortoises" are often caught in the States and kept as pets in
the gardens, and their owners mark them by cutting their initials into the
plastron. These marks heal up and widen in time like letters cut into the
bark of a tree. One of my specimens, certainly a very old one to judge from
his hooked beak, perfectly smooth and flat shell, and from the condition of
the marginals, which have the edges rubbed down quite smooth and rounded
off, has two initials and the date 1837 on its plastron. Of course there is
no proof that the date had been cut in that year, more than sixty-three
years ago, but it was done a long time ago. The scars on those parts of the
shell which touch the ground are almost effaced, and the letters and
figures have become somewhat distorted owing to the usual unequal, not
concentrical, peripheral growth. Moreover, this tortoise must have been
already adult, although not quite fully grown, since the marks are large
and were evidently put in such a size and position as to fit the available
space. I may mention that this record tortoise was, when I got it, not kept
in confinement, but had been picked up at large.
These Box-tortoises become very tame. Although fond of drinking quantities
of water in long and slowly repeated draughts, they do not go into the
water, and if they fall in accidentally they are liable to get drowned.
They enjoy a mixed diet, but animal food predominates, consisting chiefly
of snails, the shells of {363}which are passed, slugs, earthworms, maggots,
and soft caterpillars. Their fondness for slugs is all the more remarkable
since scarcely any other Vertebrate eats these slimy, sticky molluscs; but
a Box-tortoise will make a meal of two or more fat specimens of the black
slug _Arion_, and it will eat dozens of small slugs. It first deliberately
smells the prey, turns the head sidewards and gives a bite, whereupon first
the intestines and then the rest are eaten. The slime is later on scraped
off with the fore-limbs, or the head is rubbed against the grass. The
favourite time of feeding is towards dusk or in the early dewy morning, and
they are especially lively during a soft, warm rain. They also relish
various kinds of fungi and fruit, for instance half-rotten bananas. Close
observation of their habits gives us indications as to how the change from
carnivorous to herbivorous habits may have taken place. Accidentally many a
blade of grass is bitten off and swallowed together with the molluscs, also
bits of rotten wood and moss, and their excrements are often full of such
more or less digested matter. They are not very fond of basking, although
they love warmth, creeping into the grass, where they make a shallow form
by moving the shell backwards and forwards. During the cooler nights they
frequently retire into a hole or under a log of wood. They require to
hibernate. If kept in a warm house they become restless in the autumn,
refuse food, drink and feed again after some weeks, but are liable to die
during the winter. If they can find a cool place they bury themselves and
sleep for several months. If left out of doors they dig into the ground,
creep into a hole, at the bottom of which they half bury themselves, or
they hide under a heap of garden-rubbish well out of the reach of frost.
Warm April days bring them out, and the first requirement is a drink.
When walking about in search of food they assume a curious attitude, with
the shell well above the ground, the long neck stretched out and raised
high. Their temper varies individually. Some become tame readily and lose
all shyness, and creep up to their friend to take food from his fingers.
Others are decidedly shy and sulky, withdrawing with a hiss into the shell,
which in some specimens shuts almost hermetically all round, and they do
not come out until all imaginary danger is past. One of my males sulked
thus for several months, at least we never saw anything of it except the
closed shell, but it did not starve itself. {364}Propagation takes place in
the summer, the long oval hard-shelled eggs being laid in June and July.
The TYPICAL LAND-TORTOISES are easily recognised by their feet. The digits
are short, have not more than two joints, and are without any trace of
webs; the metacarpals are scarcely longer than broad. The hind-feet are
club-footed. The skin on the anterior side of the fore-limbs is covered
with strong horny scales, frequently with dermal ossifications. The
plastron is united suturally by a broad bridge with the usually strongly
arched carapace. The skull has complete postorbital and temporal arches.
The top of the head is covered with shields. The tail is short. There are
only a few recent genera, modifications of the central and typical genus
_Testudo_. The latter is cosmopolitan in the warmer temperate and tropical
regions, except in the Australian and Austro-Malayan countries.
_Cinyxis_ (Fig. 82) with a few species in Tropical Africa from the Gambia
and from Abyssinia to the Equator is remarkable for the unique modification
of its carapace, the posterior portion of which is movable, the hinge
passing between the seventh and eighth marginal and the fourth and fifth
costal plates, externally behind the seventh marginal and the second costal
shields. In the middle of the back the hinge is imperfect, the parts being
merely flexible enough to permit the posterior half of the box to be
closed. The head is covered with shields.
[Illustration: FIG. 81.–Skull of _Testudo nigrita_ s. _elephantopus_, from
the Galapagos Islands. × ½. _M_, maxillary; _Op_, Opisthotic; _Pr.f_,
prefrontal; _Pr.o_, prootic; _Pt.f_, postfrontal; _Q_, quadrate; _S.o_,
supra-occipital.]
_C. belliana_, of Northern Tropical Africa, has a small nuchal shield, and
the margin of the carapace is smooth. Length of shell up to seven or eight
inches. _C. homeana_, of West Africa, has likewise a small nuchal shield,
but the posterior portion of the carapace descends vertically, and the
marginals are strongly reverted and serrated. _C. erosa_ (Fig. 82), also
from West Africa, has no nuchal shield; the marginals are reverted and
serrated, but the posterior part of the carapace is sloping, and the
anterior {365}portion of the plastron is strongly forked in front, and
projects beyond the anterior border of the carapace. This peculiar creature
reaches a length of nine inches. When withdrawn within the shell, which is
closed behind and depressed in front, with the jagged edges of the plastron
and the anterior marginals protecting the drawn-in head, it has a very
quaint appearance. It lives entirely on fruit and other vegetable matter,
and is said to prefer to lie in the water, while _C. belliana_ is supposed
to be entirely terrestrial.
[Illustration: FIG. 82.–_Cinyxis erosa._ × ½.]
_Pyxis arachnoides_, of Madagascar, a small land-tortoise, only four inches
in length, has an immovable carapace, but the front lobe of the plastron is
hinged.
_Testudo._–The plastron is immovable, except that in old individuals of
some species, e.g. _T. ibera_, the hinder lobe develops a transverse
flexible hinge. They have existed since the Oligocene of North America and
Europe; and are now represented by nearly forty species in all the tropical
and warmer temperate countries excepting the Austro-Malayan and Australian
region. Typically terrestrial, herbivorous and frugivorous, although
occasionally varying their diet with worms, molluscs, and insects. The eggs
are hard-shelled, mostly less oval than those of the aquatic and
semi-aquatic tortoises. The males generally remain smaller than the
females, have a slightly longer tail, and have a concave instead of a flat
plastron. Most land-tortoises hibernate in the ground during the cool and
cold seasons, or they aestivate during the hot and dry months of tropical
countries, but this is not an invariable rule.
_T. graeca_, the common "Greek Tortoise." The shell is very convex, without
keels, and has a smooth, not serrated margin. {366}The nuchal shield is
narrow. The fifth or last neural shield is much broader than the others.
The supracaudal is usually divided in the median line, so that this is
really the last pair of marginals. The plastron is notched behind; the
axillary and inguinal shields are small. The scales on the anterior surface
of the fore-limbs are small, and form from half-a-dozen to ten longitudinal
rows. The hinder surface of the thigh is quite smooth. The tip of the tail
ends in a conical, horny spur. The coloration of the shell varies somewhat,
but the ground-colour is yellow, each shield with a dark brown centre and
irregular patches or confluent spots towards the margin. The plastron has
an irregular, broad black border. The soft parts are grey-yellowish. Some
specimens are rather pale, almost lemon yellow with little black; others
incline towards orange with more or less black. The middle fields of the
shields of young specimens are granular, although this area is rubbed
smooth with age; but the rest shows clearly marked concentric lines of
growth. The eyes are dark, with a brown or bluish tinge, sometimes
inclining to dark grey in very old specimens.
Full-grown females have a shell six inches in length. This species inhabits
the northern half of the Balkan Peninsula, parts of Asia Minor and Syria,
Italy, and most of the islands of the Mediterranean, from the Grecian
Archipelago to the Balearic Islands.
_T. ibera_ is closely allied to _T. graeca_, from which it differs chiefly
in the following points. The last pair of marginal shields are fused into
an unpaired supracaudal, the median line of division being almost
obliterated. The fifth neural shield is not broader, and generally a little
narrower than the others. The posterior lobe of the plastron develops with
age a transverse ligamentous hinge, and is thus rendered slightly movable,
especially in the females. The posterior margin of the carapace is slightly
expanded in old specimens. The scales of the fore-limb are large and
imbricating, and form only four or five longitudinal rows. On the middle of
the exposed posterior surface of the thighs the skin carries a strong,
conical, horny tubercle. The coloration is much like that of _T. graeca_,
except that the yellow of the young inclines to pale olive. Some specimens
are uniform brownish. This species reaches a much larger size than _T.
graeca_, old females often measuring eight inches, {367}rarely more than
nine inches in length. Its home is Morocco and Asia Minor, extending into
Persia. It also occurs in certain parts of Southern Andalucia, where it
breeds regularly, for instance, in the sandy pine-forests of the Marismas,
near the mouth of the Guadalquivir. Whether it has been introduced from
Morocco, or is indigenous, is an open question. Its specific name refers to
its Iberian home.
_T. marginata_ is worth mentioning, since it is the Greek tortoise,
although not that of the European markets, which are supplied by the other
two species. _T. marginata_ is restricted to Greece proper, where it is the
only land-tortoise. It is less closely allied to _T. graeca_ than to _T.
ibera_, of which it may be called an exaggerated form. The posterior margin
of the carapace is much expanded or flanged, and serrated. The supracaudal
is undivided, the posterior lobe of the plastron is movable, but the large
conical spur on the thighs is absent. The dorsal shields of adult specimens
are black with a small yellowish patch; the ventral shields are yellowish,
each with a large black triangular patch. The British Museum possesses a
shell 28 cm. = 11 inches in length.
The habits of these Moorish and Greek tortoises are very much alike, and
since they enjoy the distinction of frequently being kept as pets in
gardens, where they are allowed to look after themselves, a great many
incidental and odd observations have been made on them. They are
essentially vegetable feeders, but their taste varies individually and with
the season, also according to the vegetation of the country they happen to
come from. Most of them enjoy juicy plants, for instance, lettuce and
cabbage; the flowers of the dandelion attract them not merely by their
bright colour; clover is also a favourite food, and an enclosure of
grass-land with clover in it is soon cleared of the latter; grass is also
taken, in default of anything better. Some of my specimens gradually bite
large holes into gourds and pumpkins; and in Morocco I found them in the
autumn feeding entirely on the terribly astringent green fruits of the
dwarf palm _Chamaerops humilis_. The larger specimens bolted the fruit with
the stones, passing the latter. In close captivity they often learn to take
and to like bread soaked in milk or water. They drink slowly and at length,
but scarcely ever when they have succulent food. There is one thing which
they do {368}not eat, namely, "black beetles," although they are warranted
to do so by the men who hawk them in the streets. Worms, slugs, etc. are
often mentioned as part of their occasional diet, but I am not aware that
any of the hundreds which I have watched have taken such creatures, in
spite of every opportunity. Their habits are very regular. They learn to
know the geography of their domain thoroughly, and the spot selected for
sleeping will be resorted to over and over again, be it underneath some
broad leaves, under a bushy fir-tree, between a cluster of wallflowers, or
between some tussocks, or even in an almost bare corner, the attractions of
which are not at all obvious. Although their mental capacities cannot
possibly be called brilliant, they soon learn to distinguish between
different persons, and they will come up to be fed; but their memory for
localities is surprising. Here is only one instance. A tortoise which had
been put into an outhouse for hibernation was six months later taken to its
usual large enclosure, and in the afternoon it tucked itself away on the
top of a mound under precisely the same low bush where it used to sleep
during the previous autumn. It could not see that spot from where it had
been put down, and it did not meander about during the day, but after
having enjoyed the warm sun it made straight for its favourite place. Dr.
Girtanner of St. Gallen in Switzerland testifies to their appreciation of
music. When the town-band began to play on the square adjoining his garden,
all his tortoises crept as fast as possible towards the fence and remained
there motionless with heads and necks erect. When the piece was finished
they moved about, but when the next number began they were again
spellbound. This he has observed, not on one but on many occasions. That
they can hear, although their ears are not visible, but covered by the
ordinary skin, is obvious enough from the fact that during the pairing
season they emit feeble piping sounds.
They are extremely fond of basking in the hot sun, sometimes allowing
themselves to be almost baked in it, but then again at other times they
seem to be anxious to seek the shade. They rise late and go to bed early,
being absolutely diurnal. In the summer they leave their quarters when the
sun is well up, making for a sunny spot to graze. Then they lie still and
bask, unless a shower causes them to retreat under shelter. {369}After some
hours' rest they feed again, and in the afternoon, long before sunset, they
go to bed. Some winters in England are of course much more severe than any
which these tortoises experience in their native countries. Still they
manage to survive them, provided they find a place which they can burrow
into, deep enough to be out of the reach of frost; and if there is a heap
of mould, rotting weeds, and leaves, they are probably safe. Sometimes they
are restless, coming out again in unusually mild winters without, however,
taking food. If they appear too early in the spring, they run the risk of
terrible colds on prolonged wet and cold days, but in the autumn they are
hardier, and can stand several degrees of dry frost.
The pairing season begins in May, but lasts far into the summer. In Morocco
I found them pairing as late as the month of September. The preliminaries
extend over many days. The male becomes unusually active, makes a piping
sound, runs after the female, draws in its head, and knocks with its shell
against that of the female. This is repeated many times, until the female
is excited enough to raise itself upon its hind-limbs. The eggs, only two
to four in number, are laid several weeks later, and are buried in the
ground. They are roundish-oval, hard-shelled, and vary according to the
size of the female. Those of _T. graeca_ measure on the average 30 by 24
mm.; those of a large specimen of _T. ibera_ 32 to 36 by 30 mm. The
newly-hatched little creatures are still quite flexible, and apparently
soon bury themselves before beginning their active life in the ensuing
spring.
The age which these tortoises can reach is quite unknown, but there are
reliable data of individuals having been kept for many years. Rumpf[133]
kept two _T. graeca_ in his garden at Frankfort-on-the-Main, and let them
hibernate in a box with hay in the cellar. One lived 33, the other 23
years. The most famous specimen of _T. ibera_ is "Gilbert White's
Tortoise,"[134] which had been kept for more than 40 years before it came
into his possession. It used to bury itself in November and to come out in
April. It died in 1794, having reached an age of fifty-four _plus_ an
unknown number of years, since there is no record of its size when it came
to England. The same applies to every other specimen which has been, and is
being, observed as a pet. My {370}largest Morocco female, which has a shell
7 inches long, shows at least 25 concentric rings of growth on the shields;
the last half-dozen rings are very narrow, while some of those of the
central area have been rubbed down. This creature is not improbably 30
years old. A small female, which is only 5¼ inches long, has already 14
rings on its still perfect shields. Lastly, a little one, only 4 inches
long, shows 7 rings. They grow fastest when they are about 6 to 7 inches
long, and they then seem to be at their prime. White's tortoise, now
enshrined in the National Collection, was unusually large, the shell
measuring 25 cm., or nearly 10 inches; around the much-enlarged,
rubbed-down areola of each shield are about 30 very narrow rings.
_T. horsfieldi_ is easily recognised by its possessing only four claws on
the fore- and hind-limbs. It is closely allied to the species last
mentioned, which it seems to represent in the sandy districts of
Transcaspia and the Kirghiz Steppes to Afghanistan.
_T. elegans_, the "Starred Tortoise" of the southern half of India and
Ceylon, is easily recognised by the very convex carapace without a nuchal
shield, and by the beautiful markings of the other shields, each of which
has a yellow areola, whence radiate yellow streaks upon a black ground.
Moreover, the dorsal shields often form humps. It reaches the length of one
foot. Old specimens lose the beautiful yellow radiation, owing to a
considerable amount of peeling off of the horny layers.
The habits have been carefully watched by Captain Thomas Hutton,[135] who
gives the following account. The tortoises live in the grassy jungle at the
base of the hills, but owing to their colour being so blended with the
rocky nature of the ground, they are with difficulty distinguished.
Moreover, they remain concealed beneath shrubs or grass during the heat of
the day. In the rainy season they are most active, wandering about all day,
feeding and pairing. At the approach of the cold weather they select a
sheltered spot and conceal themselves by thrusting their shell into some
thick tuft of grass, remaining there in a sort of lethargic, but not
torpid, inactivity until the hot season, at which time they remain
concealed only during the heat of the day, coming out about sunset to feed.
During the hot season Hutton's captives often soaked themselves {371}in
water, and they drank a great deal. Copulation lasted about ten minutes;
the females received the males from the end of June to the middle of
October. On the 11th of November a female dug a pit at the root of a tuft
of grass, having previously watered the spot, then digging with the
hind-limbs alternately, and continuing to water the soil. In two hours she
had made a hole six inches deep and four wide; she then laid four pure
white eggs, each about 1¾ inches or 45 mm. long, and filled the hole again
with the prepared mud, pressing it well in with the feet and with the
weight of the body. The whole operation took four hours. From December to
the beginning of February these tortoises were listless, they then took
water and some lucerne, but did not come out again until the middle of
April, well in the hot season. Both males and females wrestled in a curious
way. One confronted the other, with the head and fore-limbs drawn into the
shell, and with the hind-limbs planted firmly on the ground, and in this
manner shoving against each other in any narrow space. Sometimes, if one
succeeded in placing its shell beneath the other, he tilted his adversary
over on his back, from which position he had great difficulty in recovering
himself.
_T. polyphemus_, the "Gopher Tortoise" of the south-eastern States of North
America, is one of the few American species. It is characterised by the
shape of the front lobe of the plastron, which is bent upwards, and extends
beyond the carapace. The nuchal shield is present, not narrow; the
supracaudal is undivided. The shell is much depressed, and flattened along
the vertebral region, with rounded margins. The fore-limbs are armed with
very strong claws. The general colour is very dark brown above, inclining
to black; brownish yellow below, with blackish patches. The length of the
shell is about one foot, or even eighteen inches.
The Gopher is interesting for its habits, which are described by Agassiz,
Schnee, and others. Its domicile consists of an excavation, the mouth of
which is just sufficient to admit the animal, the burrow running in an
oblique direction to the depth of about four feet. The whole passage is
sometimes more than two yards long. It expands from the entrance, and ends
in a roomy space, sometimes with a few branches of fir trees which have
been dragged in either for food or as a lining. The burrow {372}is
inhabited by one pair only. When the dew is on the grass, or after rain,
they emerge in search of food, which consists of grass, succulent
vegetables, fruit, etc. They also eat the gum that exudes from trees,
especially the resin of the pine. The eggs are laid in June, not in their
domicile, but in a separate cavity near the entrance; a set consists of
five eggs, almost round, and very large, namely, 40 mm., or more than one
inch and a half in diameter. To capture the Gopher a deep hole is dug at
the mouth of their home, into which they fall as they emerge for food. In
Southern Texas and neighbouring parts of Mexico they are represented by a
smaller and lighter coloured species.
_T. tabulata_, widely spread over Tropical South America, whence it is
often brought over as a curiosity, reaches a large size, specimens nearly
two feet in length being not uncommon. The shell is flat on the top, and is
very elongated, without a nuchal, but with an undivided supracaudal shield.
The carapace is very dark brown or black, each shield with a yellow or
orange centre; the plastron is brown and yellow, the dark colour being
mostly confined to the middle portion. The ground-colour of the skin of the
limbs is blackish, but the scales are orange or red. The head is yellow and
black. This species inhabits the forests, and lives chiefly on the fruits
of trees; in captivity they are said to take bread soaked in milk or water,
lemons, apples, bananas, cabbage, gourds, and also meat, at least the
males.
GIGANTIC LAND-TORTOISES differ from the others in no essential points
except their large size. The term gigantic is, however, applied to many of
them by courtesy only, since they do not exceed the dimensions of large
Turtles. A truly gigantic species, _T. atlas_, has left its remains in the
Sivalik Hills of late Miocene or early Pliocene date. The skull is between
seven and eight inches long, and is well preserved, but the correctness of
the dimensions of the specimen, as it now stands, restored in the National
Collection, is open to doubt. The shell was probably not more than six feet
long. Miocene and Pliocene Europe was also inhabited by large tortoises,
with shells about four feet long, _e.g._ _T. perpigniana_, whose bony
plates are one inch thick; others have been found in North America. Such
large tortoises are now restricted to two widely separated regions of the
world, namely the Galapagos Islands (which have received their name from
these creatures, _galápago_ being one of the Spanish terms for
{373}tortoise), and the islands in the Western Indian Ocean, namely the
Mascarenes (Bourbon, Mauritius, and Rodriguez), the Comoros, Aldabra, the
Amirantes, and the Seychelles. When they became extinct in Madagascar is
not known, but _T. grandidieri_ was a very large species of apparently very
recent date. Of the other islands the Comoros only were inhabited by man,
the others were devoid of any but small and harmless Mammals. It was on
these peaceful islands that large tortoises lived in incredible numbers,
and, like the Dodo of Mauritius and the Solitaire of Rodriguez, grew to a
size far beyond that of their less favourably placed continental relations.
The same applies to the tortoises of the Galapagos Islands. Plenty of food,
a congenial equable climate, and absence of enemies enabled them to enjoy
existence to the fullest extent. There was nothing for them to do but to
thrive, to feed, to propagate, to grow, and to vary. At least there was
nothing to check variation within reasonable limits. Scattered over the
many islands, they were prevented from inter-breeding, and thus it has come
to pass that not only every group of islands, but in the case of the
Galapagos almost every island, has or had its own particular kind, be these
called varieties, races, forms, or species.
There are four features of special interest. First, these tortoises grow to
a large size, and there are no small species on any of these islands.
Secondly, they vary much individually. Thirdly, each island or group of
islands has developed its own kind. Lastly, there is the widely spread
tendency to reduce the thickness of the bony plates of the carapace, in
spite of its size. In some cases, notably _T. vosmaeri_ of Rodriguez, the
bony shell is reduced to apparently the utmost limit compatible with
mechanical safety. The horny shields are, or were, however, well developed,
sometimes much more so than in other recent land-tortoises. Whatever were
the original reasons for the development of a strong shell in tortoises,
they cannot have prevailed in these islands.
Where did all these tortoises come from, and how did they get to these
oceanic islands? Accidental transport or migration are out of the question.
Land-tortoises are drowned within a few hours. Moreover, there are none of
their kind on the continents of Africa, Asia, and South America, although
they had a much wider distribution in past geological ages. Consequently we
have to assume that they are descendants of tortoises once populating the
land which, except the islands, lies now below {374}the western Indian
ocean. The existence of this, "Lemuria" or "Gondwana," came to an end in
Mid-Tertiary times. The large tortoises on the remaining continents died
out–in any case they are gone, while those which lived on, or retreated to,
what became the present islands, survived and flourished.
The tortoises were not left in peace with the advent of man, who found that
they were good to eat. They were first exterminated on the Mascarene
Islands. In 1759 four small vessels were specially appointed for the
service of bringing tortoises from Rodriguez to Mauritius; one vessel
carried a cargo of 6000; and altogether more than 30,000 were imported into
Mauritius within the space of eighteen months. Dr. Günther very properly
remarks that many of these tortoises must have been small-sized specimens,
and that many of them were probably used for provisioning passing
Government vessels. Anyhow an inter-insular traffic was carried on, and
there are records of superfluous tortoises having been turned loose, at the
end of the voyage, in distant islands, even in Java. Importation and
exchange of choice specimens, by way of presents, seems also to have taken
place. All this makes it now actually impossible to trace the original
habitat of the few surviving specimens with anything like certainty. At the
beginning of this century the large tortoises had been nearly cleared off
most of the islands, and at the present time only the south island of
Aldabra enjoys the reputation of still possessing some really indigenous
tortoises. The few survivors on the other islands are said to have been
introduced. The small stock at Aldabra is now under Government protection.
Representatives of various species will linger on for a little time to
come, when they are kept as pets on some tropical islands, but those which
have been brought to Europe are of course doomed.
We can mention only a few of the large tortoises which have become famous,
not to say historical. A fascinating résumé of the whole complicated
question has been given by Dr. Günther.[136]
_Testudo gigantea_ s. _elephantina_ s. _hololissa_ s. _ponderosa_,
originally confined to the North Island of Aldabra, where this {375}kind
has been completely exterminated, is now still to be found in the
Seychelles in considerable numbers, introduced there by planters, and kept
in a state of semi-domestication. A very large specimen was received by the
Hon. Walter Rothschild, at Tring, in 1893. In 1897 its shell measured 40¼
inches in length, 52¼ over the curve, and 50 inches across the curve
transversely; it weighed 358 lbs. The measurements taken in previous years
are unfortunately not free from mistakes. "Whenever the temperature was
over 60° F. this tortoise had a free run of 350 acres of grass park, and
when the temperature showed permanently below 58°, it was kept in an orchid
house from September to June. When at liberty in the park it lived entirely
on grass, but in the hothouse it fed on carrots, cabbage, lettuce, and
several other vegetables"; it was also very fond of rotten fruit. To this
species belongs the large tortoise which has been living at St. Helena for
more than the last hundred years.
_T. daudini_ is the species of the South Island of Aldabra. Voeltzkow, in
1895, succeeded in carrying off seven specimens. He gives the following
description:–The island is an atoll, cut through in three places, with a
greatest length of about twenty miles. The chief hindrance in the search
for the tortoises is the impenetrability of the island. The soil consists
entirely of sharp water-worn corals, with their points uppermost, while the
whole is covered with such thick masses of low scrub, that a way has to be
cut with an axe, so that an extended search over a large area is out of the
question. To land on the outside is dangerous, on account of the heavy
surf; while landing from the inside of the atoll is much hindered by the
dense thickets of mangrove trees. As drinking water, and that very bad, is
only found in one place, rainwater has to be collected from the natural
hollows, and carried along in tanks. Thousands of mosquitoes prevent one
remaining over night in those places which the tortoises frequent. Then at
last, when one has discovered, by a stroke of luck, one of these creatures,
in the thick scrub, where they hide during the heat of the day, the real
hard work begins, namely, the conveyance of the beast. Six reached Europe
alive, two of them were sent to Frankfort, and the four others to Hamburg.
Mr. Rothschild received a male of _T. daudini_, which, until its recent
death, was the largest living tortoise known. The length {376}of its shell
was 55 inches, or 67½ inches over the curve; total weight 560 lbs. This
specimen had a chequered career. Although its original home must have been
the Aldabra atoll, it had been known for many years on Egmont Island, one
of the Chagos Islands. According to tradition, it had been there some 150
years, but the first settlement on that island was formed from Mauritius
only at the beginning of this century. The owner of the tortoise, M.
Antelme, took it to Mauritius, whence it came to England. On the Egmont
Island it used to bury itself for six months in the ground without eating
anything.
[Illustration: FIG. 83.–_Testudo daudini_ (above) and _T. abingdoni_
(below). × 1/20.]
_T. sumeirei._–This kind is supposed to have been the species peculiar to
the Seychelles. In 1766 five large tortoises were brought from the
Seychelles to Mauritius by Chevalier Marion de Tresne. Of these only three
were alive in 1898, two in {377}Mauritius and one in London; the latter
specimen soon died in the Zoological Gardens. One of the two survivors, the
last of their race, is famous. It was kept at Port Louis, and when
Mauritius became a British possession in 1810, the tortoise was especially
mentioned and taken over. It still lives there in the grounds of the
barracks of the garrison. According to the proverbial oldest inhabitants it
had in 1810 already reached its present size, namely, a shell-length of
about 40 inches with a greatest circumference of 259 cm. = 8 feet 6 inches.
Total weight 160 kilo = about 358 lbs. When walking it stands 63.5 cm. =
25.4 inches high, with the plastron about 15 cm. or 6 inches above the
ground, and it can then carry with ease two full-grown men on its back.
This old male is now nearly blind, but is otherwise of regular habits and
in good health. Although it has been known for nearly 150 years it had to
wait for its scientific name until the year 1892.
Another famous individual is the Colombo tortoise. It is supposed to have
come to Colombo from the Seychelles in 1798. It died in 1897. To judge from
photographs, this specimen, a male, may possibly belong to _T. sumeirei_,
in spite of the very flat shell, which is 53½ inches in length.
Leaving aside the remains of sub-fossil tortoises, _e.g._ the thin-shelled
_T. vosmaeri_ of Rodriguez, and several kinds which have been dug out in
the Mare-aux-songes of Mauritius, one of which had a markedly forked and
prolonged anterior plastral lobe, rather resembling that of the Pliocene
Sivalik _T. atlas_, we now turn to the tortoises of the Galapagos Islands.
They existed in enormous numbers towards the end of the seventeenth
century, when Dampier visited those islands. Hundreds were exported and
scattered early in the nineteenth century. When the islands became a penal
settlement of Ecuador, the introduction of convicts and pigs proved
detrimental to them, but Darwin found them still present in 1835 on most of
the islands. His classical account of these old giants is to be found in
the _Voyage of the Beagle_. They lived on the succulent cactus plants,
leaves of trees, berries, and a kind of _Usnea_, a lichen pendant from the
trees. They collected regularly at certain pools and springs, leading to
which were regular well-trodden paths, formed by the coming and going of
the tortoises. He calculated that they could walk a distance of about four
miles in one day. During {378}the time of propagation the males emit a
hoarse bark, which can be heard a hundred yards off. The round eggs measure
about 5 cm. or 2 inches in diameter, and are laid in the month of October,
about one dozen making a set.
Nearly every island had apparently its own kind. They are all remarkable
for their small head and the length of their neck, which is decidedly
longer and more slender than that of the Eastern tortoises. The most
peculiar looking are or were _T. ephippium_ and _T. abingdoni_, the shell
of which is extremely thin, with large lacunae in the osseous plates. The
profile of the shell is somewhat saddle-shaped, with the horny shields
partly concave and turned upwards at the sides. The general colour of these
and the other Galapagos tortoises is black. _T. ephippium_ still survives
on Duncan Island. Of _T. elephantopus_ s. _vicina_ Baur collected
twenty-one specimens in 1893 on Albemarle Island. Some of them are still
comparatively young, only 16 inches long. A large one was killed, and,
being hard up for water, Baur and his companions drank the five cups full
of fluid contained in the pericardial sac; they found it most refreshing,
and tasting somewhat like the white of an egg. One monster is said to have
measured 56 inches over the curve, with a skull 7.12 inches in length. Mr.
Rothschild received one of this kind alive–a much-travelled specimen. It
came to England from Sydney, whether it had been brought in 1880 from
Rotuma Island, north of the Fiji group. There it had probably been left
with others by Captain Porter, who, on his voyage from the Galapagos in
1813, distributed several young tortoises from his stock among the chiefs,
and permitted a great many to escape into the bushes and among the grass.
The shell of this specimen measured 49½ inches in length, 56 over the
curve.
FAM. 6. CHELONIDAE (_Turtles_).–The limbs are paddle-shaped, and the shell
is covered with horny shields. Only two recent genera, with three species,
widely distributed in the seas.
The neck is short and incompletely retractile. The temporal region of the
skull is completely roofed over above and laterally by the parietals,
postfrontals, squamosals, quadrato-jugals and jugals. All these bones are
much expanded, and form the additional or false roof. The parietals are
especially large, and are in broad contact with the squamosals. Nasals are
absent. The nares are bordered by the small premaxillaries, the
maxillaries, {379}and the prefrontals. The choanae are enclosed by the
palatines, which are separated by the vomer, and are posteriorly in broad
contact with the pterygoids. The latter are connected with descending
processes of the parietals by epipterygoids. The foramen magnum is bounded
not only by the supra-occipital and the lateral occipitals, but also by the
basi-occipital. For the skeleton see Fig. 65, p. 320. The pubic and
ischiadic symphyses are connected by a narrow cartilaginous band. The pubis
has a large, broad, lateral process, but the ischium is devoid of such a
process. The paddles of the fore- and hind-limbs are produced by an
elongation of the metacarpal and metatarsal bones and of most of the
phalanges, and these have no condyles; most of the carpal and tarsal
elements are flattened, and additional width is given to the hands by the
much enlarged pisiform bone. The number of phalanges of the five fingers is
2, 3, 3, 2, 2; that of the five toes, 2, 3, 3, 3, 2.
[Illustration: FIG. 84.–Skull of _Thalassochelys caretta_; cf. also Fig.
63, p. 317. _A_, Dorsal view; _B_, ventral view; _F_, frontal; _Jg_, jugal;
_Mx_, maxillary; _Op_, opisthotic; _P_, parietal; _Pal_, palatine; _Pr.f_,
prefrontal; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_, quadrate; _Quadr_,
articular surface of quadrate; _Qj_, quadrato-jugal; _S.o_,
supra-occipital; _Sq_, squamosal.]
The carapace is heart-shaped and very flat. The nuchal plate has no
rib-like processes. The eight neurals form a continuous series, and the
short tail is covered by two or three pygal plates besides the unpaired
last marginal. The number of all the {380}marginals is 23, sometimes 25
individually. The plastron (Fig. 66, p. 321) is composed of the usual nine
plates, which, however, remain entirely free from the marginals, and are
only loosely connected with each other, enclosing a very large unossified
space. The horny shields covering the plastron number 13, and there is a
series of about 5 inframarginals (Fig. 61, 6, p. 315). There are normally
12 pairs of marginal shields, a nuchal, 5 neural, and 5 or 7 costal
shields. Whilst the number of these dorsal shields is pretty constant in
_Chelone_, it is subject to an astonishing amount of individual variation
in _Thalassochelys_.
The Chelonidae are a highly specialised offshoot of the Cryptodira adapted
to marine life. Fundamentally they agree most with the Testudinidae,
paradoxical as this may appear at first sight. There is nothing primitive
about them except the complete series of inframarginal shields. Fossil
forerunners of marine turtle-like creatures appear in the Upper Jurassic
deposits of Europe and North America. The numerous genera have been grouped
together as Thalassemydidae and Chelonemydidae. They are more or less
intermediate between Chelonidae and _Emys_-like Testudinidae, the carapace
being not too much flattened and broadened out, the fontanelles between the
ribs are mostly small, the plastral bones are still broad, enclose a
smaller ossified space, and there is still a bony bridge in most cases. The
paddle-shape of the limbs is less pronounced, and sometimes only indicated.
In some forms, especially _Lytoloma_, from the Upper Cretaceous and Eocene
of North America and Europe, the anterior portion of the skull is much
longer than in the Chelonidae, the vomer and the premaxillaries are
elongated, and the anterior portion of the roof of the mouth, with the
corresponding parts of the lower jaw, seems to have carried crushing pads.
Some of the best-known Upper Jurassic genera are _Eurysternum_ and
_Idiochelys_; _Plesiochelys_ from the Purbeck and Wealden; _Allopleuron
hofmanni_ from the Upper Cretaceous of Belgium approaches _Chelone_ by the
large fontanelles between the small marginal and the short costal plates.
True Chelonidae are very rare and imperfect in the Mid-Tertiary strata, but
both recent genera seem to have existed since Pliocene times.
The few recent Chelonidae are entirely marine, going on land only in order
to deposit their eggs in the sands of unfrequented shores. Their
distribution, in conformity with their oceanic life, {381}is almost
cosmopolitan within the warmer zones, but not a few find their way far into
the temperate seas. They are all eagerly hunted by man either for food or
for the sake of the tortoiseshell.
_Chelone._–With only four pairs of costal shields. Carapace with large
persisting fontanelles between the costal and marginal plates. Two species.
_Ch. mydas_ (the "Green or Edible Turtle"), has when adult a nearly smooth
shell, all the shields being juxtaposed, fitting closely into each other,
and becoming quite smooth with age. The neural shields of younger specimens
have a feeble keel. The twenty-five shields which surround the carapace
form a smooth, or but indistinctly serrated rim. The head is covered with
one pair of prefrontal shields, the others are small. The horny beaks of
the upper and lower jaws have denticulated outer edges, those of the upper
jaw having two pairs of strong denticulated ridges. The limbs have
generally only one claw, namely on the first digit. This claw, although
sometimes curved and thick, and more than an inch in length, is blunt. The
general colour is olive or brown above, with yellowish spots or blotches;
the under parts are pale yellowish. This species attains a large size, with
a length of shell of nearly four feet, but the usual length of full-grown
specimens is three feet, and these weigh, when in good condition, more than
three hundredweight. Their home is in the Atlantic, Indian, and Pacific
Oceans, but there are certain regions in which they are more common than in
others. Famous centres are the Island of Ascension, the West Indies, and
the coast of Mosquito, at least for commercial purposes. As they require
sandy, easily accessible beaches for the deposition of their eggs, they
congregate in certain parts of the world more than in others, and being
strictly vegetable feeders, they are naturally bound to the coasts,
although they are sometimes met with far out at sea. Their chief food
consists of algae, and of _Zostera marina_, the edible "Dulce," which grows
plentifully in the lagoons of the coast of Florida. When they have eaten
their fill, they are said to chop off more of these plants, and roll them,
together with the adherent mud, into balls of the size of a head, and these
balls, receding with the tide, are followed by the Turtles.
Whilst in the water they are caught in various ways, with {382}nets or
harpoons. In some parts of the world the natives follow them in a boat, and
when they espy a turtle crawling along the bottom, a man, attached to a
rope, dives in, clasps it, and is brought up by his companions together
with his prey. Turtles are fond of basking asleep, floating on the surface,
and they are then harpooned from a stealthily approaching boat. The most
original mode of catching them is that used by the natives of Torres
Straits, Madagascar, and Cuba. The turtle-fishers go out in the boat to a
spot frequented by grazing turtles; a long string is tied to the tail of a
fish, _Echeneis_, a member of the Mackerel family, and the _Echeneis_,
anxious to get away to protective shelter, makes for a turtle, and attaches
itself to the turtle's plastron by means of the large sucking apparatus on
the top of its head and neck-region. The men are guided by the string, and
the turtle is gently coaxed up towards the surface or followed into shallow
water, where it is either harpooned or dived for. It is curious that this
use of the _Echeneis_ exists in such widely separated parts of the world,
the natives of which cannot have any knowledge of each other. These modes
of catching turtles are sportsman-like, but the greatest and most wanton
destruction is practised at their breeding places. In conformity with the
wide distribution of these creatures, the time of breeding is not the same
everywhere. In the West Indian region, and in the Straits of Malacca, it
falls within the period of April to June; on the coast of West Africa it
occurs from September to January. The females come to their breeding places
from afar, reconnoitre the beach carefully, are extremely wary and shy,
taking alarm at the slightest disturbance, and at last crawl on land. Well
out of the reach of the tide the female scoops out a hole in the sand,
deposits about one hundred or more of its round, rather parchment-shelled
eggs, covers the nest carefully, obliterating all traces of the dug-out
sand, and makes again for the sea by another route. At least they are said
to make a sort of circuitous route so that nobody can tell the position of
the nest, which may be anywhere beneath the broad trail left by the heavy
creature on its way from and back to the sea. The nest is discovered by
probing the sand with sticks. The time of incubation is not known, but
according to Agassiz, lasts at least seven weeks.
{383}[Illustration: FIG. 85.–Three turned Turtles, a Seal, and Albatrosses,
Laysan Islands, north-west of the Sandwich Islands. From a photograph
belonging to the Hon. W. Rothschild.]
{384}The "turning" of turtles is a cruel and wanton operation, since
frequently many more are turned over and left to perish than are taken
away. Men lying in ambush watch the beast, or they approach the lonely
sandy shore by boat, and rush the helpless creatures when these are
surprised in sufficient numbers. It takes several men to lift a full-grown
specimen. It is therefore necessary to secure them by turning them over
with poles or by their flippers, lest they should crawl away. On board ship
they are either put into tanks or tied with ropes on deck, covered with a
moistened cloth; and occasionally a piece of bread, soaked in sea-water, is
thrust into the parched mouth. In London they are kept in large tanks,
often in considerable numbers, but since they take no food in captivity, or
rather because it is difficult to supply them with the right sort, they are
not kept long. After the head has been cut off, the body is suspended for a
day or two, in order to drain it of the blood. It is not only the meat and
the fat which are used for the making of the famous soup, but also the
thick and dense layer of subcutaneous tissue which lines the inside of the
shell.
Tennent describes a revolting spectacle exhibited in the markets of Jaffna,
in Ceylon. The flesh of the turtles is sold piecemeal by the Tamil
fishermen, while the animals are still alive. At certain seasons, says the
same authority, the flesh of turtle on the south-west coast of Ceylon is
usually avoided as poisonous, but some lamentable instances are recorded of
neglect of this, and consequent sickness, followed by coma and death. In
the Gulf of Manaar specimens are frequently found between four and five
feet in length; and on one occasion, in riding along the seashore north of
Putlam, he saw a man in charge of some sheep, resting under the shade of a
turtle shell, which he had erected on sticks to protect him from the sun.
In connexion with this curious sight, Tennent quotes Aelian's statements,
copied by him from Megasthenes' _Indica Frag._ lix. 31, that in the Indian
ocean turtles occur which measure fifteen ells, so that not a few people
may find ample shelter beneath a single shell.
_Ch. imbricata_ ("Hawksbill Turtle").–The number of shields covering the
carapace is the same as in _Ch. mydas_, but they strongly imbricate, or
overlap each other from before backwards, until the animal is very old,
when the shields become juxtaposed.
{385}[Illustration: FIG. 86.–_Chelone imbricata_ ("Hawksbill Turtle"),
young. × ½.]
In young specimens, under one foot in length, each of the neural and costal
shields is strongly keeled, the three rows of keels converging towards the
posterior end of the shell. The neural series of keels is almost
continuous, and remains longest, even in half-grown specimens. The twelve
pairs of marginal shields form at first a strongly serrated sharp edge; the
serrations disappear gradually on the front portion, but remain on the
posterior half of the shell. The horny covers of the jaws form a hooked
beak, with sharp but smooth or feebly denticulated margins. The fore- and
hind-flippers have two claws. The young are pale brown above, blackish
below; the shell of the adult is beautifully marbled with yellow on a rich
dark-brown ground; the plastron is yellow. The shields and scales of the
head and limbs are dark brown, with yellow margins. The top of the head is
covered by a large unpaired frontal and a pair of prefrontal or
interorbital shields. This Turtle does not reach the size of the green or
edible kind; the largest shell on record is in the National Collection, and
measures 85 cm. = 34 inches in length. They range over all the tropical and
subtropical seas. They are apparently strictly {386}carnivorous, living
upon fish and molluscs, the shells of which they crunch. Although not
eaten, they are much persecuted on account of their shells, the horny
shields of which are the "tortoiseshell" of commerce. A large specimen
yields up to 8 lbs. Few of the shields are, however, thick enough to be
manufactured into the larger articles which art and fashion delight in, but
if heated in oil, or boiled, they can be welded together under pressure,
and be given any desired shape. In genuine articles of Oriental manufacture
these welds can generally be detected, or their compound nature is
indicated by the beautiful pattern, which is too regular in the imitations
now common. Even the shavings and leavings can be welded and moulded into
large pieces. The stripping of the shields has been described by Sir E.
Tennent. "If taken from the animal after death and decomposition, the
colour of the shell becomes clouded and milky, and hence the cruel
expedient is resorted to of seizing the turtles as they repair to the shore
to deposit their eggs, and suspending them over fires till heat makes the
plates on the dorsal shields start from the bone of the carapace, after
which the creature is permitted to escape to the water. At Celebes, where
the finest tortoise-shell is exported to China, the natives kill the
turtles by blows on the head, and immerse the shell in boiling water to
detach the shields. Dry heat is only resorted to by the unskilful, who
frequently destroy the tortoise-shell in the operation." The cruel process
described above is resorted to "for economy's sake," the Singhalese
believing that such maltreated turtles regenerate the shields, to be caught
and shipped again. Since none of them are actually re-caught in the
mutilated condition, this is looked upon as a proof of the correctness of
the treatment. It is more likely that they die.
New shields can be reproduced only if the underlying Malpighian layer of
cells (_cf._ Fig. 68, B, p. 323) is not killed by the roasting. However,
Dr. Charles Hose, with his long experience in Borneo, is positive that
numerous individuals are there caught which have imperfectly mended shells,
the shields of which do not imbricate, are thin, and almost worthless.
It is commonly believed that the same individuals return again and again to
the same spot for laying. This is very likely the case. Tennent mentions
that in the year 1826 a Hawksbill was taken near Hambangtotte, which bore a
ring attached to one of its fins, that had been placed there by a Dutch
{387}officer thirty years before, with a view of establishing the fact of
these recurring visits to the same beach. The same homing instinct has been
observed in some females of the Green Turtle, which, having been brought
from the Tortugas Keys to Key West off the south end of Florida, escaped,
and were, a few days later, re-caught at the Tortugas. On the other hand,
experiments made with turtles at Ascension are said to have had no result.
_Thalassochelys_, with five pairs of costal shields. The carapace is
completely ossified in the adult, leaving no fontanelles between the ribs
and the marginals.
_Th. caretta_ (the "Loggerhead Turtle").–The shields of the carapace
imbricate only in young specimens, in the adult they become smooth and
juxtaposed. The margin is serrated posteriorly. The carapace of the young
has three strong keels. The intergular shield is very small or absent. The
marginals, including the nuchal, usually number 23, rarely 25. The large
head is armed with hooked jaws, the crushing surface of the horny upper
beak has a median prominent ridge. The top of the head has a pair of
shields in front of the unpaired frontal. The flippers of the young have
claws on the first and second digits; in the adult usually only that of the
first digit remains. The general colour of the shell is uniform brown
above, yellowish below. Very young specimens are uniform dark brown or
blackish above and below.
Large individuals have a shell about three feet and a half in length. The
Loggerhead is carnivorous, and is commercially of no value. Its habits seem
to be the same as those of the other Turtles, but it has a much wider
distribution. Besides all the tropical and intertropical seas, it inhabits
the Mediterranean, and is an accidental visitor to the western coasts of
Europe, especially Portugal and the Bay of Biscay. It has been caught
several times on the coast of Belgium, and an old female containing 1150
eggs was captured in 1894 on the Dutch coast. In 1861 one was caught near
Penman, on the coast of Banffshire, and a second in the completely
land-locked Loch Lomond.[137] It has been more frequently recorded from the
coast of Devon and Cornwall.
The most interesting feature of the Loggerhead is the {388}astonishing
variability in the number of the horny shields of the carapace. The normal
number of shields of the carapace, leaving out the marginals and counting
the nuchal as the first neural, is 6 neurals and 5 pairs of costals, in all
16. The greatest number of dorsal shields observed is 8 neurals and 8 pairs
of costals, in all 24. Many of the intermediate combinations have been
observed, there being, for instance, specimens with 8 neurals and 16, 14,
13, 12, or 11 costals, the latter not being always in pairs, but unequal on
the right and left sides; or there are 7 neurals with 20 to 16 costals, or
6 neurals with 20, 19, 18, 17, or 16 costals. The interesting fact in
connexion with these variations is, moreover, that some of the shields are
much smaller than the others, sometimes mere vestiges in all stages of
gradual suppression, and that the abnormalities are much more common in
babies and small specimens than in adults. The importance of these
"orthogenetic" variations has been discussed on p. 326.
SUB-ORDER 2. PLEURODIRA.–_Neck bending laterally and tucked away in the
niche formed between the anterior portion of the carapace and plastron.
Pelvis ankylosed to the shell, the broadened tops of the ilia to the
carapace, the distal ends of the pubes and ischia to the plastron._
Freshwater tortoises, almost entirely carnivorous, inhabiting South
America, Australia, Africa, and Madagascar. Fossil forms are known from the
Jurassic epoch onwards.
Owing to the strong connexion of the iliac bones with the costal plates the
sacrum has become practically abolished, the sacral ribs being reduced to
one pair (the posterior of the original two pairs) or being absent. The
centra of the cervical vertebrae articulate by cup and ball joints. The
formation of the temporal region of the skull varies considerably in the
three families, some genera lacking the complete zygomatic arch, while
others have a narrow parieto-squamosal arch bridging over the temporal
fossa, or the latter is completely roofed over by the laterally expanded
parietal, which meets the jugal and quadrato-jugal. The quadrate is always
trumpet-shaped; the rim of the tympanum is complete, but the posterior part
of the trumpet remains open. The basisphenoid, pterygoids, and palatines
form a broad and flat roof to the mouth. The vomer is large, and separates
the palatines in the Chelydidae; it is very much {389}reduced or absent in
the Pelomedusidae, in which the palatines meet. All the Chelydidae, except
_Chelys_, have nasal bones which remain distinct from the prefrontals. The
choanae lie in front of the palatines, divided by the vomer when this is
present, but they are not roofed in ventrally.
The ilia are solidly ankylosed in the adult with the neighbouring costal
plates, mostly with the last two pairs, sometimes also with the pygal
plate. The lateral processes of the pubes fuse with the xiphiplastra. The
ischia are also attached to the same plastral elements.
The carapace is flat and completely ossified. The nuchal plate is always
conspicuous, much larger than the neurals, and these are often reduced by
being encroached upon by the eight pairs of costal plates, which then meet
in the dorsal line. In _Sternothaerus_ all the eight neurals are present
and form a continuous row. In most of the other genera they are reduced to
seven, the last being squeezed out. In _Rhinemys_ they are reduced to the
second, third and fourth and an isolated fifth, and in _Hydraspis_ they are
all gone. The pygal plate is always, even in _Sternothaerus_, separated
from the last neural by the eighth pair of costals. The marginals number
23, but in _Carettochelys_ only 21.
The carapace is covered with horny shields, except in _Carettochelys_. The
nuchal is absent in the Pelomedusidae and in a few Chelydidae (_Elseya_ and
a few species of _Emydura_). In _Hydromedusa_ the nuchal is shut in by the
anterior marginals, simulating a sixth neural. The plastron is composed of
the usual nine elements, but the Pelomedusidae possess an additional pair,
the meso-plastra, inserted between the hyo- and hypo-plastra. The bridge is
strong, connected with the carapace by suture. In _Sternothaerus_ the front
lobe of the plastron is movable. The intergular shield is always present;
it is terminal, forming part of the front margin, except in _Chelodina_,
where this shield, although large, is shut in behind the gulars (cf. Fig.
61, 4 and 5, p. 315).
Although the Pleurodira are a peculiarly specialised group, one of the
oldest Chelonian fossils known seems to belong to them. _Proganochelys_,
represented by a complete shell, nearly 2 feet long, has been found in the
Upper Keuper Sandstone of Würtemberg. _Plesiochelys_, of the Upper Jurassic
of Switzerland, has eight neural and three supracaudal plates, but is
without the {390}ischiadic plastral ankylosis. _Pleurosternum_, of the
English and Continental Purbeck beds, has meso-plastral plates like the
recent Pelomedusidae. _Rhinochelys_, of the Cambridge Greensand, has a
broad parieto-postfrontal roof, and large nasal bones. Forms like
_Podocnemis_, now restricted to South America, occur in the Eocene of
Europe. One of the most aberrant Chelonians is _Miolania_, from the
Plistocene of Queensland and from Lord Howe's Island, remarkable for its
huge size and the thick armour on the head and tail; the head especially
carries large paired projections, one pair of which extends horizontally
like powerful horns, recalling the queer Theromorphous _Elginia_.