The division of the secondary formations, called “Oolite,” takes its
name from the most characteristic of its constituents, which is a
variety of limestone composed of numerous small grains, resembling the
“roe” or eggs of a fish, whence the term, (from the Greek _oon_, an egg,
_lithos_, a stone). The oolite, however, includes a great series of beds
of marine origin, which, with an average breadth of thirty miles, extend
across England, from Yorkshire in the north-east to Dorsetshire in the
south-west.
The oolite series lies below the Wealden, and where this is wanting,
below the chalk, and consists of the following subdivisions, succeeding
each other in the descending order:—
Oolite.
Upper. Portland stone and sand.
Kimmeridge clay.
Middle. Coral rag.
Oxford clay.
Lower. Cornbrash and forest marble.
Great oolite and Stonesfield slate.
Fuller’s earth.
Inferior oolite.
Upon the portion of the island representing the oolite series, the most
conspicuous of the restored animals of that period is—
No. 7.—The Megalosaurus.
The Megalosaurus, as its name implies (compounded by its discoverer, Dr.
Buckland, from the Greek _megas_, great, and _sauros_, lizard), was a
lizard-like reptile of great size, “of which,” writes Dr. Buckland,
“although no skeleton has yet been found entire, so many perfect bones
and teeth have been discovered in the same quarries, that we are nearly
as well acquainted with the form and dimensions of the limbs as if they
had been found together in a single block of stone.”
The restoration of the animal has been accordingly effected, agreeably
with the proportions of the known parts of the skeleton, and in harmony
with the general characters of the order of reptiles to which the
Megalosaurus belonged. This order—the Dinosauria (Gr. _deinos_, terribly
great _sauros_, a lizard)—is that to which the two foregoing huge
reptiles of the Wealden series belong, viz., the Iguanodon and
Hylæosaurus, and is characterised by the modifications already
mentioned, that fitted them for more efficient progression upon dry
land. The Iguanodon represented the herbivorous section of the order,
the Hylæosaurus appears, from its teeth, to have been a mixed feeder,
but the Megalosaurus was decidedly carnivorous, and, probably, waged a
deadly war against its less destructively endowed congeners and
contemporaries.
[Illustration: No. 7. Megalosaurus.]
Baron Cuvier estimated the Megalosaurus to have been about fifty feet in
length; my own calculations, founded on more complete evidence than had
been at the Baron’s command, reduce its size to about thirty-five
feet:[3] but with the superior proportional height and capacity of
trunk, as contrasted with the largest existing crocodiles, even that
length gives a most formidable character to this extinct predatory
reptile.
As the thigh-bone (_femur_) and leg-bone (_tibia_) measure each nearly
three feet, the entire hind-leg, allowing for the cartilages of the
joints, must have attained a length of two yards: a bone of the foot
(metatarsal) thirteen inches long, indicates that part, with the toes
and claws entire, to have been at least three feet in length. The form
of the teeth shows the Megalosaurus to have been strictly carnivorous,
and viewed as instruments for providing food for so enormous a reptile,
the teeth were fearfully fitted to the destructive office for which they
were designed. They have compressed conical sharp-pointed crowns, with
cutting and finely serrated anterior and posterior edges; they appear
straight, as seen when they had just protruded from the socket, but
become bent slightly backwards in the progress of growth, and the fore
part of the crown, below the summit, becomes thick and convex.
A minute and interesting description of these teeth will be found in Dr.
Buckland’s admirable “Bridgewater Treatise” (vol. i. p. 238), from which
he concludes that the teeth of the Megalosaurus present “a combination
of contrivances analogous to those which human ingenuity has adopted in
the construction of the knife, the sabre, and the saw.” The fossils
which brought to light the former existence of this most formidable
reptile, were discovered in 1823, in the oolitic slate of Stonesfield,
near Oxford, and were described by Dr. Buckland, in the volume of the
“Geological Transactions” for the year 1824.
Remains of the Megalosaurus have since been discovered in the “Bath
oolite,” which is immediately below the Stonesfield slate, and in the
“Cornbrash,” which lies above it. Vertebræ, teeth, and some bones of the
extremities have been discovered in the Wealden of Tilgate Forest, Kent,
and in the ferruginous sand, of the same age, near Cuckfield, in Sussex.
Remains of the Megalosaurus also occur in the Purbeck limestone at
Swanage Bay, and in the oolite in the neighbourhood of Malton, in
Yorkshire.
Mr. Waterhouse Hawkins’s restoration, according to the proportions
calculated from the largest portions of fossil bones of the Megalosaurus
hitherto obtained, yields a total length of the animal, from the muzzle
to the end of the tail, of thirty-seven feet; the length of the head
being five feet, the length of the tail fifteen feet; and the greatest
girth of the body twenty-two feet six inches.
Nos. 8 & 9.—Pterodactyles of the Oolite.
To the right of the Hylæosaurus, on the rock representing the greater
oolite formation, are restorations of species of Pterodactyle
(_Pterodactylus Bucklandi_, No. 9), smaller than and distinct from those
of the chalk formations. The remains of Buckland’s Pterodactyle are
found pretty abundantly in the oolitic slate of Stonesfield, near
Oxford.
Nos. 10 & 11.—Teleosaurus.
On the shore beneath the overhanging cliff of oolitic rock are two
restorations, Nos. 10 and 11, of a large extinct kind of crocodile, to
which the long and slender-jawed crocodile of the Ganges, called
“Gaviàl” or “Gharriàl” by the Hindoos, offers the nearest resemblance at
the present day. Remains of the ancient extinct British gavials have
been found in most of the localities where the oolitic formations occur,
and very abundantly in the lias cliffs near Whitby, in Yorkshire. The
name Teleosaurus (_telos_, the end, _sauros_, a lizard), was compounded
from the Greek by Professor Geoffroy St. Hilaire, for a species of these
fossil gavials, found by him in the oolite stone at Caen, in Normandy,
and has reference to his belief that they formed one—the
earliest—extreme of the crocodilian series, as this series has been
successively developed in the course of time on our planet.
The jaws are armed with numerous long, slender, sharp-pointed, slightly
curved teeth, indicating that they preyed on fishes, and the young or
weaker individuals of co-existing reptiles. The nostril is situated more
at the end of the upper jaw than in the modern gavial: the fore-limbs
are shorter, and the hind ones longer and stronger than in the gavial,
which indicates that the Teleosaur was a better swimmer; the vertebræ or
bones of the back are united by slightly concave surfaces, not
interlocked by cup and ball joints as in the modern crocodiles, whence
it would seem that the Teleosaur lived more habitually in the water, and
less seldom moved on dry land; and, as its fossil remains have been
hitherto found only in the sedimentary deposits from the sea, it may be
inferred that it was more strictly marine than the crocodile of the
Ganges.
The first specimen of a Teleosaur that was brought to light was from the
“alum-schale” which forms one layer of the lofty lias cliffs of the
Yorkshire coast, near Whitby. A brief description, and figures, of this
incomplete fossil skeleton were published by Messrs. Wooller and
Chapman, in separate communications, in the 50th volume of the
“Philosophical Transactions,” in 1758. Captain Chapman observes, “it
seems to have been an alligator;” and Mr. Wooller thought “it resembled
in every respect the Gangetic gavial.” Thus, nearly a century ago, the
true nature of the fossil was almost rightly understood, and various
were the theories then broached to account for the occurrence of a
supposed Gangetic reptile in a petrified state in the cliffs of
Yorkshire. It has required the subsequent progress of comparative
anatomy to determine, as by the characters above defined, the essential
distinction of the Teleosaur from all known existing forms of
crocodilian reptiles.
Very abundant remains, and several species, of the extinct genus have
been subsequently discovered: but always in the oolitic and liassic
formations of the secondary series of rocks.
The oolitic group of rocks are very rich in remains of both plants and
animals: many reptiles of genera and species distinct from those here
restored have been recognised and determined by portions of the
skeleton. Extremely numerous are the remains of fishes, chiefly of an
almost extinct order (_Ganoidei_), characterised by hard, shining,
enamelled scales. But the most remarkable fossils are those which
indisputably prove the existence, during the period of the “Great” or
“Lower Oolite,” of insectivorous and marsupial mammalia—_i.e._, of
warm-blood quadrupeds, which, like the shrew or hedgehog, fed on
insects, and, like the opossum, had a pouch for the transport of the
young. The lower jaw of one of these earliest known examples of the
mammalian class, found in the Stonesfield slate, near Oxford, may be
seen at the British Museum, to which it was presented by J. W. Broderip,
Esq., F.R.S., by whom it was described in the “Zoological Journal,” vol.
iii., p. 408.
It is interesting to observe that the marsupial genera, to which the
above fossil quadruped, called _Phascolotherium_, was most nearly
allied, are now confined to New South Wales and Van Diemen’s Land; since
it is in the Australian seas that is found the _Cestracion_, a
cartilaginous fish which has teeth that are most like those fossil teeth
called _Acrodus_ and _Psammodus_, so common in the oolite. In the same
Australian seas, also, near the shore, the beautiful shell-fish called
_Trigonia_ is found living, of which genus many fossil species occur in
the Stonesfield slate. Moreover, the Araucarian pines are now abundant,
together with ferns, in Australia, as they were in Europe in the oolitic
period.