§ 20.

SPIROLINITES.

325

foraminifera and infusoria, with spines of sponges, and a considerable intermixture of polygonal spicula, resulting from the decomposition of the large fibrous bivalve termed *Inoceramus*, so common in the chalk. Intermingled with the decidedly cretaceous forms, are minute fresh-water shells, which have probably been derived from some modern deposit; and many shields or cases of small marine crustaceans, termed *Cytherina*; which are related to the Cyprides.*

20. SPIROLINITES.—The chalk and flints often contain beautiful examples of a foraminiferous chambered shell, of a crosier-like form, termed *Spirolinites*; of which several species were discovered some years since, by the Marquess of Northampton. I subjoin enlarged figures of two species (Lign. 60); and the following communication, with which I have been honoured by his Lordship.

> "I willingly comply with your desire to communicate a short note on the Sussex *Spirolinites*, one species of which you have been pleased to distinguish by my name. I have found these fossils in flint at Brighton, Kemp town, Rottingdean, Lewes, Hast ings, Steyning, Chichester, West Stoke, and in the Isle of Wight; and one specimen in France. I have discovered about two hundred of these minute chambered

* The only notice of the Charing animalculites, is contained in Mr. Williamson's memoir above referred to. It is to be hoped the intelligent and liberal discoverer, Mr. Harris, will publish a full account of the geological relations and organic contents of this curious deposit.

LIGN. 60.—SPIROLINITES IN FLINT;
from the South Downs.*

Fig. 1. Spirclinites Lyellii.
2. S. Murchisoni.

326

THE WONDERS OF GEOLOGY.

LECT. IV.

shells in flint, but only two in chalk. The specimens which I have collected constitute four distinct species. 1. The one to which you have been pleased to give the appellation of S. Comptoni. 2. Spirolinites Lyellii, distinguished by the horizontal chambers one above the other, in the coiled portion. 3. S. Stokesii, which I name after our friend Charles Stokes, Esq.; and this name has the further advantage of pointing out the locality, West Stoke, near Chichester, from which I obtained this unique specimen, and where other spirolinites abound. The fourth you must allow me to designate S. Mantelli. The distinctive characters of these species are too obvious to require detailed description. The transverse chambers in S. Lyellii (Lign. 60, fig. 1) are a striking peculiarity of structure. I am inclined to believe that there are other species in my collection, but the irregularity in the fractured sections of these minute chambered shells, renders it difficult to arrive at accurate conclusions on this point.

"NORTHAMPTON."

"Castle Ashby, January 1, 1838."

21. CRINOIDEA.—The *Crinoidea*, or lily-shaped animals, are but sparingly distributed in the chalk—a circumstance, as you will hereafter find, in striking contrast with the zoological characters of some of the older secondary formations. Stems of *Pentacrinites* occur both in the chalk and galt; and there is a small species of *Apiocrinite*, which is peculiar to the white chalk.*

A remarkable cretaceous fossil of this class is the *Marsupite*, which I thus named from its resemblance, when closed, to a purse. The Marsupite (Lign. 61) was a crinoideal animal, of a sub-ovate form, having the mouth, which was surrounded by arms, or tentacula, near the centre. The skeleton was composed of crustaceous, hexagonal plates,

united by suture, and the arms, which are

* Geology of the South-East of England, p. 111.

LIGN. 61.
MARSUPITES MILLERI;
from the chalk, Brighton.

§ 23.

STAR-FISHES OF THE CHALK.

subdivided into a few branches, were formed of little bones, or ossicula; the whole was invested with a muscular tissue, or membrane. When floating, the creature could spread out its tentacula like a net, and by closing them, seize its prey and convey it to the mouth. This figure (Lign. 61) is restored from specimens which separately exhibit the parts here represented.*

22. STAR-FISHES OF THE CHALK.†—Of the radiated animals termed Asterias, or star-fish, several genera occur in the English chalk and greensand, and in the cretaceous strata of the Continent. In the Sussex chalk, beautiful examples of the Goniaster, or cushion-star, have been found; but they are more frequently met with in the white chalk near Gravesend, Northfleet, Purfleet, and other Kentish localities. The cabinet of the Marquess of Northampton contains exquisite specimens of Goniaster, partly imbedded in flint; similar fossils have been obtained from the siliceous rock, called whetstone, of Devonshire. Several fine examples of an undescribed Asterias of the radiated type, with elongated rays, and large ossicula, have been collected from the Dover chalk: and a splendid specimen from that locality, as perfect as if recently dredged up from the sea, is in the beautiful collection of Mrs. Smith, of Tunbridge Wells. Detached ossicula are very abundant in some of the strata; and there are layers of the grey or lower chalk, wholly made up of the debris of star-fish, minute spines of echini, &c.

23. ECHINITES.‡—Those remarkable animals, the Echini, or sea-urchins, are too well known to require particular description. Their spherical shell, or case, is composed of

* There is another species often found with the above, in which the plates are covered with rugous markings; it is the *M. ornatus* of the late Mr. Miller.

† Medals of Creation, vol. i. p. 332.

‡ See Medals of Creation, vol. i. chap. xi. p. 340.

328

THE WONDERS OF GEOLOGY.

LECT. IV.

polygonal plates, closely fitted to each other; and the surface is divided vertically by bands, like the meridians of a globe, having rows of double perforations. The shell is studded over with papillæ, which vary in size, in the different species, from mere granular points to large well-defined tubercles. To these papillæ, spines are attached, which also present great variety of figure and decoration;* these are the instruments of motion, and as on the death

LIGN. 62.—ECHINITES AND SPINES, FROM THE CHALK.

(Figs. 5, 7, one-third less than the originals.)

Fig. 1. Cidaris diadema. 2, 4, 9. Spines of Cidaris. 3. Nucleolites. 5. Anan-
chytes ovatus. 6. A tubercle of a Cidaris. 7. Spatangus cor marinum. 8. Spines
and portion of the shell of a Cidaris in flint.

of the animal, the tendons by which they were fixed to
the shell decompose, the rarity of fossil specimens, with
these processes attached in their natural position, is readily
explained. The Echini, both recent and fossil, comprise a

* Medals of Creation, vol. i. p. 348.

§ 24.

ECHINITES OF THE CHALK.

329

great variety of species, which are arranged in numerous sub-genera, for the convenience of study; but I can notice only a few of the common forms.

The helmet-shaped echinites (Lign. 62, fig. 5) are extremely abundant, and in some localities occur in shoals, and in every gradation from the young to the adult state. Siliceous casts, formed by the decomposition and removal of the shell from the flint with which it was filled, are common in gravel and on ploughed lands. The cordiform variety (fig. 7) is very abundant, and gives rise to the heart-shaped flints of our gravel-pits. The elliptical species (fig. 3) is common in the greensand. The turbinated echini (Cidares), are beautifully embossed with papillæ: a small species (fig. 1) is frequent in the chalk and flints of Kent; the larger varieties possess tubercles (fig. 6), surrounded by elegant margins, and are otherwise richly ornamented. Some spines are slender, and covered with asperities (fig. 2); others almost smooth (fig. 9), and club-shaped (fig. 4); it is not often that spines are found in contact with the shell (fig. 8); this however, is occasionally the case, and from the chalk at Gravesend, and other localities in Kent, splendid examples have been discovered; some with groups of large spines attached to the tubercles, as in the living state.

24. SHELLS OF THE CHALK.—The bivalve shells, or conchifera of the chalk, are very numerous; of one genus alone (Terebratula), above fifty species are enumerated. Oysters, scallops, arcas, tellens, and other familiar marine shells abound, but the species differ from the recent. With these known genera are many which, so far as our present knowledge of the inhabitants of the deep extends, are extinct. Two or three species of *Cirrus* are not unusual in the English white chalk; but the univalves are few; and the only specimen of a large simple spiral univalve with which I am acquainted is a species of *Dolium*, of which several

§ 24.

SHELLS OF THE CHALK.

331

The sub-globular terebratulæ, both the common and the striated varieties, are very abundant.* Another bivalve equally numerous, is an elegant shell, having one valve covered with long spines (Lign. 63, fig. 8), the *Plagiostoma spinosum*.† A bivalve with a fibrous structure (*Inoceramus*, Lign. 63, fig. 4), very brittle, and having a crenulated hinge of a peculiar construction, presents numerous species; some of which are small and delicately striated, while others are two feet in diameter, and deeply furrowed.‡ The substance of these shells closely resembles in structure that of the recent *pinnæ*; and from its fragility, fragments are very common in chalk, flint, and even in pyrites.§ The *Galt* contains two species of this genus, which have been found in almost every locality, and appear to be restricted to this division of the chalk; they are the *Inoceramus concentricus* (Lign. 63, fig. 1), and *I. sulcatus* (fig. 3); a hybrid occurs in the Folkstone beds, partaking of the characters of both. I have discovered a species of *Spherulite* (*S. Mortoni*) in the chalk near Lewes, in Sussex; but *Hippurites*, so common in the cretaceous strata of the Continent, have not been noticed.||

The shells of the Marl, Galt, and Greensand, amount to many hundred species: those of the whetstone pits of Blackdown, in Devonshire, being completely silicified, and changed into silex, jasper, or chalcedony.¶

* Medals of Creation, vol. i. p. 379.

† This shell was formerly supposed to be peculiar to the chalk strata, but specimens have been discovered by Mr. Pratt in eocene deposits. Medals of Creation, vol. i. p. 390.

‡ Ibid. p. 393. § Ibid. p. 396.

|| Ibid. p. 428. No true *Hippurites* have been found in the English chalk; the shells of the family Rudistes hitherto met with have the characters assigned to the genus *Spherulites*.

¶ The shells of the cretaceous formation are most fully described and figured in M. D'Orbigny's beautiful work on the fossils of France —Palæontologie Française.

332

THE WONDERS OF GEOLOGY.

LECT. IV.

25. CEPHALOPODA OF THE CHALK.—The most striking feature in the marine fauna of the chalk, as contrasted with that of the tertiary and modern formations, is the great preponderance of multilocular cephalopoda.* In the tertiary, and existing tropical seas, one genus (the *Nautilus*) occurs abundantly. The beauty, elegant form, and remarkable internal structure of the recent shell, have rendered it in all ages an object of admiration; yet an accurate knowledge of the organization of the animal to which it belongs, has but recently been obtained. The Nautilus, and the allied fossil genera, may be regarded as Sepiæ or Cuttle-fish inhabiting chambered shells, which are furnished with an apparatus to impart buoyancy, and enable the animals to swim on the surface, or sink to the depths of the ocean at pleasure.

A few remarks on the recent types will serve to render the subject intelligible. The *Sepia*, or *Cuttle-fish* of our seas is of an oblong form, composed of a jelly-like substance, covered with a tough skin; the mouth, which is central, is furnished with horny mandibles, much resembling the beaks of a parrot. The animal has two large eyes, and eight arms studded with rows of little cups, or suckers, which are powerful instruments both of locomotion and prehension. The soft body of the sepia is supported by a skeleton, formed of a single bone or *osselet* of a very curious structure; when dried and reduced to powder it is the substance called *pounce*. The Cuttle-fish has a membranous sac, which secretes and retains a dark-coloured fluid, resembling ink; this the animal can eject when pursued, and by thus rendering the water turbid, escape from its enemies. This fluid, properly prepared, forms the colour termed *sepia*, which is so much employed in the arts.

* See Medals of Creation, vol. ii. p. 456, for an account of the Cephalopoda.

§ 28.

AMMONITES OF THE CHALK.

335

formations, and certain species are restricted to particular rocks. Thus, for example, the chalk marl of Sussex abounds in two species (*Lign.* 63, *figs.* 7, 9), which very rarely occur either in the chalk above, or in the galt below; and in every locality of the marl in England, and on the Continent, these have been met with.* The membranous tube of the siphuncle sometimes occurs in a fossil state, as may be seen in this ammonite from the chalk marl near Lewes, in which a large portion remains; the black substance of these tubes has been analyzed, and found to consist of animal membrane, permeated by carbonate of lime.†

Ammonites vary in size from a few lines to twelve or fourteen feet in circumference; at low water on those parts of the Sussex coast where the chalk forms the base of the shore, enormous specimens are often seen imbedded. In some of the marls and clays of the chalk, hundreds of ammonites occur in clusters.

28. TURRILITE, HAMITE, &c.—*Baculites, Turrilites, Hamites, Scaphites, and other genera of multilocular shells, abound in the chalk-marl, galt, and greensand. The turritlite (Lign. 63, fig. 2), may be described as an ammonite twisted in a spiral, instead of a discoidal form: and the hamite (Lign. 63, fig. 6), as a similar structure in the shape of a hook, coiled up at the smaller extremity. These shells sometimes attain a large size; the turrilite before you,

* See my Fossils of the South Downs, for figures of many chalk Ammonites: also Mineral Conchology; Geological Journal; Medals of Creation, vol. ii. p. 489; and M. D'Orbigny's Palæontologie.

† Dr. Prout is of opinion that the black colour has originated from decomposition; the oxygen and hydrogen of the animal membrane having escaped, and carbon evolved, as happens when vegetable matter is converted into coal, under the process of mineralization. The lime has taken the place of the oxygen and hydrogen, which existed in the pipe before decomposition.—Dr. Buckland's *Bridgewater Essay*, p. 352.

336

THE WONDERS OF GEOLOGY.

LECT. IV.

which is the finest example known, would, if perfect, exceed
two feet in length; it possesses traces of the siphuncle.
Very large hamites and scaphites have been found in the
greensand of Kent, Isle of Wight, and other places. The
first specimens of turrilites, hamites, and scaphites, from
the British strata, were discovered in my early researches,
in Hamsey marl-pits, near Lewes.*

LIGN. 66.—BELEMNITES; one-third natural size.

Fig. 1. *Belemnitella mucronata*;† from chalk, Brighton. On the right of the figure is a view of the aperture; and beneath it a transverse section of the belem-nite, showing the radiated structure.

2. Portion of a Belemnite containing the internal chambered shell, called the phragmocone.

3. *Belemnitella quadrata*; from Beauvais, France; the quadrangular cavity is shown in the upper figure on the left.

4. *Belemnites dilatatus*; from the Greensand, France.

29. THE BELEMNITE.—Among the innumerable relics of marine animals which occur in the secondary deposits,

* See Sowerby's Mineral Conchology, vol. i. tab. 18. From the recent cuttings through the chalk-marl at Offham, in forming the railway from near Keymer, through Lewes, to Newhaven, I obtained a fine series of all these genera. Figures of Turrilites, Scaphites, &c., are given in Medals of Creation, vol. ii. pp. 502, 504.

† See Medals of Creation, vol. ii. p. 462. *Belemnitella* is the generic name of the belemnites having a fissure down the front of the alveolus, or cavity which receives the phragmocone.

§ 30.

BELEMNITES OF THE CHALK.

337

there are none that have excited so much curiosity, and given
rise to so many conjectures as to their nature and origin,
as the fossils termed *Belemnites* by geologists, and which
are generally known as *thunderbolts*. These are long,
cylindrical, or fusiform stones, more or less pointed at one
extremity, and having at the other and larger end a conical
cavity, which is either occupied by a chambered shell, or
filled up with the clay, sand, or stone, in which the be-
lemnite happens to be imbedded. The substance of these
bodies is invariably calcareous spar, of a radiated structure
(*Lign.* 66, fig. 1). Such are the usual characters of these
fossils, of which there are numerous species; certain forms
abounding in the cretaceous strata. A very common chalk
belemnite is figured *Lign.* 66, fig. 1; and a peculiarly
transparent species from the Galt, *Lign.* 63, fig. 5. These
bodies were the osselets of cephalopods allied to the *Sepia*,
which possessed an ink-bag, mandibles, large eyes, and arms
furnished with acetabula or suckers, and slender, elongated,
hooks.*

30. CRUSTACEANS OF THE CHALK.† — Specimens of
several genera of crustaceans have been obtained from the
Sussex chalk; among these are three or four species of
*Astacus* or Lobster, in which the filiform antennæ, the
abdominal segments, and the caudal appendage, or tail, are
preserved.‡

In the Galt, the crustaceans hitherto discovered belong
to very small species. I have obtained from Ringmer,
near Lewes, and Folkstone, specimens of several extinct
forms, which are related to Indian genera. § In the
Speeton clay of Yorkshire, Professor Phillips has dis-
covered a beautiful species of Crayfish. || The green-
sand of Kent, Dorsetshire, and the Isle of Wight, has

* Medals of Creation, vol. ii. p. 469.

‡ Ibid. p. 537.

§ Ibid. p. 532.

z

† Ibid. p. 536.

|| Ibid. p. 540.

338

THE WONDERS OF GEOLOGY.

LECT. IV.

yielded many remains of this family; the strata at Atherfield, especially, abound in several species of Lobster.*

In the limestone of St. Peter's Mountain, the claws of a small species of Crab are frequently discovered (Lign. 67), but without any other vestiges of the animal. M. Faujas St. Fond, and Latreille, have very ingeniously explained this

LIGN. 67.—CLAWS OF A FOSSIL HERMIT-CRAB; FROM MAESTRICHT.

(Pagurus Faujasii.)

fact, by showing that these remains belonged to a parasitical species of *Pagurus*, which, like the common hermit-crab of our seas, had the body covered by a delicate membrane, the claws alone having a shelly case; hence the latter might be found in a fossil state, while of the other parts of the crustacean no traces would remain.

31. FISHES OF THE CHALK.—The fossil fishes of the white chalk were known only by the teeth, which abound

* Some of the layers of the greensand at Atherfield contain so many remains of two or three species of small Astaci, as to be termed the "Lobster beds." See my Geology of the Isle of Wight, pp. 225, 232: and the vignette of the title-page of that volume.

§ 32.

SCALES OF FISHES.

339

in almost every quarry, until my researches in the chalk-pits around Lewes brought to light many extraordinary specimens, and showed how such delicate remains could be developed.* Professor Agassiz, by whose genius and labours this department of palæontology has been most successfully elucidated, has adopted a classification of fishes, founded upon the peculiar structure of the scales—a method of

LIGN. 68.—SCALES OF THE FOUR ORDERS OF FISHES.

Fig. 1. Scale of *Lepidotus*; a fish of the *Ganoid* order.

2. — Ray; — Placoid —.

3. — Salmon; — Cycloid —.

4. — Beryx; — Ctenoid —.

great utility to the geologist, since the mutilated state in which the fossil remains of fishes generally occur, often renders futile all attempts to refer them to the orders and genera of other systems of Ichthyology.†

32. SCALES OF FISHES.—M. Agassiz includes all fishes

* I believe the Fossils of the South Downs (1822) contained the first published figures of fishes from the English chalk.

† Recherches sur les Poissons Fossiles, par Louis Agassiz: five vols. folio of coloured figures, and two quarto vols. of letter press.

z 2

340

THE WONDERS OF GEOLOGY.

LECT. IV.

in four orders, which are distinguished by the structure of
the scales, as exemplified in the following tables (Lign. 68).

Order I. The Placoid; the skin covered with irregular enamelled plates, as in the Rays, Sharks (Lign. 68, fig. 2).

II. The Ganoid; the scales of an angular form, and composed of plates of horn or bone covered with a thick layer of enamel; as in the Sturgeon (Lign. 68, fig. 1),

III. The Ctenoid; the scales formed of plates, which are toothed or pectinated on their posterior margin or edge, like a comb; as in the Perch (Lign. 68, fig. 4).

IV. The Cycloid; the scales composed of simple laminæ of horn or bone, without enamel, and having smooth borders; as in the Salmon (Lign. 68, fig. 3).*

LIGN. 69.—SCALES OF FISHES IN FLINT.

Fig. 1. A fragment of flint containing two scales, of the natural size.

2. One of the scales highly magnified; it belongs to the species of *Beryx*, figured in *Lign. 68*.

3. The other scale highly magnified; it belongs to the species of *Smelt*, figured in *Lign. 72, fig. 1*.

Patches of scales are very abundant in some of the white chalk strata in Sussex and Kent; and occasionally very perfect examples of the entire body of the fish, with the fins attached, are obtained; which by proper dissection may be

* See Medals of Creation, vol. ii. p. 593.

§ 33.

FOSSIL TEETH OF SHARKS.

341

beautifully displayed.* Scales and teeth are occasionally found in flint; sometimes adherent to the surface, and in other instances imbedded in the stone. A fragment of flint to which two minute scales are attached is figured in *Lign.* 69, fig. 1; and the scales, highly magnified, are represented in *figs.* 2 and 3.

33. TEETH OF SHARKS, &c.—Teeth of several genera of fishes abound in the cretaceous deposits: and of these, by far the greater number belong to the Sharks; a family which in the ancient, as well as in the modern seas, appears to have been confined by no geographical limits. A group of some of the usual forms is represented in *Lign.* 70. These teeth possess a high polish, and are in an excellent state of preservation; they generally occur detached, owing to the decomposition of the jaws, which from their cartilaginous nature are but seldom preserved. A few specimens of the fishes termed *Hybodus*,† have, however, been found with several rows of teeth attached to the jaws.

Large flat teeth, having a series of deep angular plaitings on the crown, surrounded by a border of papillæ (*Lign.* 70, *figs.* 4, 5), are very abundant, and are commonly known as “palates.” They belong to a genus of the shark family called *Ptychodus* (rugous teeth), allied to the *Cestracion* or *Port Jackson Shark*. A group of teeth has lately been found in the chalk by the Marquess of Northampton, which differ but little from those of the recent living species. Dorsal rays, or fin-bones, belonging to these fishes are occasionally met with in the chalk; the first known examples were figured in my *Fossils of the South Downs* (*Tab.* 39).‡

* For directions how to clear chalk fishes, see Medals of Creation, vol. ii. p. 673. All my best specimens, most of which are figured in the work of M. Agassiz, are now in the British Museum.

† Medals of Creation, vol. ii. p. 609; Geology of the Isle of Wight, p. 233.

‡ Medals of Creation, vol. ii. p. 605.

342

THE WONDERS OF GEOLOGY.

LECT. IV.

Several dorsal spines of a Shark allied to the Dog-fish (*Acanthias*) of our coasts, were found in the same quarries.*
Vertebræ, and other remains of sharks, have been obtained

LIGN. 70.—TEETH OF SHARKS; FROM THE CHALK NEAR LEWES.

Fig. 1. Galeus pristodontus.

3. Notidanus microdon.

5. Ptychodus polygurus.

2. Lamna crassidens.

4. Ptychodus polygurus.

6. Lamna elegans.

in considerable numbers from the chalk of the south-east of
England.

The mandible, or anterior part of the maxillary bone of
a fish belonging to a very remarkable family, of which the
*Chimæra* is the only living type,† was found in the chalk
marl at Hamsey, near Lewes, many years since, associated
with turrilites, hamites, &c. and subsequently examples of

* Medals of Creation, vol. ii. p. 609.

† Ibid. p. 619.

§ 34.

FOSSIL FISHES OF THE CHALK.

many other forms have been discovered in secondary and
tertiary strata; thus affording evidence that the ancient seas
were inhabited by several genera of this curious and now
limited group.*

LIGN. 71.—MAXILLARY BONE OF A FISH ALLIED TO THE CHIMÆRA; FROM THE CHALK NEAR LEWES.

(Endaphodon Mantelli; half the natural size.)

34. **Hypsodon.**—Teeth of large fishes, belonging to that division called *Sauroid*, from their combining in their structure certain characters of reptiles,† have been found in the white chalk, galt, and greensand. They are of a conical form, longitudinally striated externally, and bearing a general resemblance to those of crocodiles, for which they were formerly mistaken. Remains of several other large fishes are preserved in various private collections, but have not yet been scientifically examined.

There is however a genus of extinct fishes, allied to the
Pikes, which has been established by M. Agassiz from
some vertebræ and other bones. It is named *Hypsodon*,
from the straight and pointed form of the teeth. A jaw
with teeth, some vertebræ, and the *os hyoides*, of this fish

* Sir P. G. Egerton has very recently laid before the Geological Society an admirable memoir on the fossil Chimæroid fishes.

† Medals of Creation, vol. ii. p. 650.

344

THE WONDERS OF GEOLOGY.

LECT. IV.

were first discovered in the chalk near Lewes, and are figured in Pl. xlii. of my Fossils of the South Downs. Their reptilian character led me to consider them as belonging to a saurian, until I obtained a considerable portion of the cranium, jaws with teeth, the bone that articulates the lower jaw with the skull, and several biconcave vertebræ, imbedded in a block of chalk, and belonging to the same individual.*

35. FOSSIL SALMON. (Lign. 72. fig. 1.)—Of the cycloid order, or fishes with scales of a cycloid or circular form and smooth margins, and composed of plates of horn or bone without enamel, there are two or three species belonging to the Salmon family, which occur in the lower chalk near Lewes. These ichthyolites are exceedingly beautiful, and generally have the body uncompressed, and as round and perfect as when the fishes were alive. The entire cranium, opercula, branchial rays, and fins, are preserved in some examples. From the close affinity of these fishes to the Smelt (*Osmerus*), they have been named *Osmeroides*. In one specimen I succeeded in clearing away the chalk, so as to expose the entire fish, which lies six inches in relief, being attached by the back to the block of stone; the mouth is open, and the opercula, or gill-covers, and the branchial arches are expanded; the pectoral, dorsal, and ventral fins are in their natural position.†

Even to those whose curiosity has not previously been awakened by the Wonders of Geology, the examination of these petrified inhabitants of the ancient chalk ocean can-

* This fine specimen is now in the British Museum, with other remains of the Hypsodon.

A splendid specimen of jaws and premaxillary bones, with numerous teeth, that differ from the Hypsodon Lewesiensis in being slightly curved, is in the choice collection of Toulmin Smith, Esq. of Highgate. Two species of Hypsodon have been identified in the London clay.

† Medals of Creation, vol. ii. p. 663.

§ 36.

FOSSIL FISHES OF THE CHALK.

345

not fail to excite deep interest; and I have often seen the
man of fashion, as well as the philosopher, gaze in mute
astonishment on these "relics of a former world."

36. MACROPOMA. (Lign. 73. fig. 2.)—A fish, bearing
some semblance to the large Carps in its general outline,
but essentially differing in its structure, is the most re-
markable ichthyolite which my researches in the chalk
quarries around Lewes, have brought to light;* but it was
not till after many years of persevering research that the
nature of the original was fully illustrated. This fish when
at maturity must have exceeded two feet in length: its
skeleton is massy, indicating a powerful frame; and its thick
scales, strong fins, and sharp teeth, show that it was a vorac-
ious animal, capable of pursuing and overtaking live prey.
The head is very large; being nearly equal to one-fourth the
length of the body. The scales are large, and are covered
on the exposed surface with pointed elongated cylinders.
The opercula are very long.† The rays of the fins are
large and rigid, especially those of the anterior dorsal,
which are armed on each side with rows of sharp spines.
The tail is very large, rounded, and fan-shaped, with
strong equal rays, supported by the inferior and superior
spinous processes of the caudal vertebræ. The form
of the jaws and teeth is also remarkable, but my limits
will not admit of further details. In every example
I have found the remains of what I supposed to be
the air-bladder, but which M. Agassiz affirms to be the
stomach. It is an oblong cylindrical body, apparently
terminating at one end in a cul-de-sac: its surface

* Fossils of the South Downs. It is described under the name of *Amia Lewesiensis*. The largest specimen therein figured (Pl. 38) I presented to Baron Cuvier, and it is now in the museum of the Jardin des Plantes.

† Whence the name *Macropoma*; μακρύδος, long, and πῶμα, oper-
culum.

346

THE WONDERS OF GEOLOGY.

LECT. IV.

has a squamous appearance, owing to the separation and partial exfoliation of the membranes of which its walls are composed. Under the microscope, the ramification of the vessels through these tissues is distinctly seen. *Coprolites* (or fossil excrements), having a slightly convoluted form, are often found with the remains of the Macropoma.*

37. BERYX; AND OTHER FISHES OF THE CHALK.—It would require a separate work to notice in detail even my own discoveries in this division of the fauna of the chalk ocean, which comprise more than forty species. I must content myself with briefly noticing some of the most interesting examples, and referring to M. Agassiz's splendid volume, in which all the chalk fishes known at the time of its publication are beautifully figured, and philosophically interpreted. But so rapid has been the progress of discovery that many new genera have since been brought to light.

Certain fossil fishes closely allied to the *Perch*, were my first treasures of this class, and are among the most abundant of the Sussex ichthyolites. They belong to the genus *Beryx*, of which there are two species now living in the seas of Australia. Outlines of two of the most common species of the Sussex and Kentish chalk, are given in *Ligns*. 75 and 76. The horny capsule of the globe of the eye is often preserved in these fossils.†

The annexed figures (*Ligns*. 72, 73, 74, 75, 76) are restored outlines of seven of the Sussex ichthyolites, executed by Mr. Joseph Dinkel, the eminent artist employed by M. Agassiz.‡

* Consult Recherches sur les Poissons Fossiles, tome ii. part. 2dc. p. 174.

† Medals of Creation, vol. ii. p. 659.

‡ Mr. Dinkel now resides in London; at 13, Great James-street, Bedford-row.

352

THE WONDERS OF GEOLOGY.

LECT. IV.

*Lign. 72, fig. 1. Osmeroides Mantelli.* This figure conveys a correct idea of the general outline of the fossil Salmons, found in the Lewes chalk.

*Lign. 72, fig. 2. Acrognathus boops.* I have seen but one specimen of this small fish; the relatively large jaw and eye are indicated by the name. The upward bend of the caudal extremity is doubtless accidental.

*Lign. 73, fig. 1. Aulolepis typus.* This is likewise an unique specimen of a fish six inches long, having scales of a peculiar character.

*Lign. 74. Dercetis elongatus.* Fragments of the elongated subcylindrical body of this fish very frequently occur in the chalk of Sussex, Kent, and Hampshire. Examples, two feet and even more in length, are occasionally met with; and yet but two instances are known, in which any vestiges of the skull, or of the tail, can be traced. In the specimen from which the figure was taken, the parts represented were clearly defined.* The Dercetis had on the sides three rows of dermal scutcheons (like those of the Sturgeon), that extended over the body, and the intervals between them were covered with small scales; in most specimens the latter only remain.

*Lign. 75. Beryx radians.* *Lign. 76. Beryx Lewesiensis.* Several examples of these ancient fishes of the Perch tribe have been found as perfect as in these delineations. Another and more delicate species, with a very small head (*Beryx microcephalus*), is occasionally obtained from the chalk-marl, exquisitely preserved.

In the other subdivisions of the cretaceous formation, remains of fishes occur more or less abundantly in various parts of England, the Continent, and America. One locality only can here be mentioned; Glaris in Switzerland has long been celebrated for the profusion and variety of its ichthyolites, which occur in a very hard, black, laminated shale. This shale is highly bituminous, and can scarcely be distinguished lithologically from some of the most

* See Medals of Creation, vol. ii. p. 658.

§ 38.

REPTILES OF THE CHALK.

353

ancient slate rocks. But from the characters of the fossil
fishes, which are all of cretaceous genera, M. Agassiz was
enabled to solve the problem, and prove that the Glaris
slates belong to the chalk formation; the altered condition
of the rock having resulted from the effect of high tempe-
rature under great pressure.

In concluding this cursory notice of the fishes of the
cretaceous epoch I would remark that two-thirds of the
genera, and almost all the species, are extinct, but related
to tertiary forms. This result is in accordance with that
derived from the examination of the zoophytes, mollusca,
and other organisms, which have come under our notice in
the course of this review.

38. REPTILES OF THE CHALK.—The remains of reptiles discovered in this formation, though not very numerous, are sufficient to arrest attention, when contrasted with the entire absence of all traces of warm-blooded animals. We perceive, as it were, the first indications of that remarkable discrepancy in the relative numerical proportion of the mammalia and the reptilia, which distinguishes the secondary from the tertiary and modern epochs.

The most extraordinary of the reptiles peculiar to the
chalk, is the Mosasaurus of Maestricht (ante, p. 311). A
few vertebræ, apparently of this animal, have been found
in the white chalk near Lewes. In the cretaceous strata of
America, my friend Dr. George Morton, of Philadelphia,
discovered teeth, which are specifically identical with the
Maestricht reptile.* In the Essex chalk, portions of a
jaw, with teeth, belonging to a saurian of the same genus,
were discovered by Mr. Edward Charlesworth many years
since; the symmetrical form, and smooth surface of the
teeth, separate them from the above, and Mr. Charlesworth
has named the species *Mosasaurus stenodon*.

* Dr. Morton's Synopsis of the Cretaceous Strata of N. America, Pl. XI. fig. 9.

A A

354

THE WONDERS OF GEOLOGY.

LECT. IV.

Teeth of crocodiles are mentioned by Baron Cuvier as
having been obtained from the chalk at Meudon.

A considerable portion of a spinal column composed of
concavo-convex vertebræ, with many ribs, and part of the
pelvis, of a small lizard, were found in the chalk near Maid-
stone; and another specimen of the anterior portion of the
spine, with part of the cranium, has since been obtained by
Mrs. Smith, of Tunbridge Wells. A jaw, with numerous
subulate teeth, anchylosed by their base to an alveolar
parapet of bone, as in the recent Iguana, has been dis-
covered in chalk near Cambridge. These relics are re-
ferred by Prof. Owen to the same species of reptile, which
he has named *Raphiosaurus.*\*

Remains of two genera of marine reptiles, the Ich-
thyosaurus and Plesiosaurus, occur, though rarely, in the
white chalk of Sussex, Kent, and Dorsetshire.†

From the greensand of Kent one of the most interesting
specimens of the Iguanodon has been obtained; and in the
same strata at Hythe, have been found numerous bones of a
gigantic marine reptile, to which are also ascribed certain
large conical striated teeth, that occur in the greensand of
various localities.‡

That the *Pterodactyles*, those marvellous flying reptiles,
existed during the cretaceous epoch, we have proof in
several specimens of bones of the extremities, and of part of
the cranium, and jaws with teeth, obtained from the chalk
pit at Burham, in which the fossil turtle, presently to
be noticed, was discovered.§

* Geol. Trans. vol. vi. Pl. 39; Medals of Creation, vol. ii. p 758.

† I have received a vertebræ of a Plesiosaurus from the chalk near Blandford, through the kindness of J. Shipp, Esq.

‡ Hence the name *Polyptychodon* has been given to this reptile.
Medals of Creation, vol. ii. p. 728.

§ Figures and descriptions of this chalk Pterodactyle are given by
Mr. Bowerbank in the Geological Journal for 1846.

356

THE WONDERS OF GEOLOGY.

LECT. IV.

delineated in the drawing, *Lign.* 77, can be removed, so as to expose the bones of the plastron, or sternal plates, beneath. This fossil is six inches in length, and three and a half in breadth.

40. SUMMARY.—The characters of the Cretaceous Formation, as shown by these investigations, are those of a vast oceanic basin, filled up with organic and inorganic debris, and innumerable remains of the successive generations of marine animals which lived and died in its waters, through periods of incalculable duration.

The fossil fuci indicate that the chalk ocean possessed the usual marine flora; while the drifted masses of wood bored by teredines, and the fir-cones, stems of cycadous plants, leaves of ferns, and bones of terrestrial reptiles, prove that its shores were bounded by dry land, which was clothed with forests, and inhabited by colossal oviparous quadrupeds. Of the higher orders of animals no unquestionable relics have yet been discovered.

A TABULAR ARRANGEMENT OF THE FOSSIL FISHES OF THE CHALK OF THE SOUTH-EAST OF ENGLAND, IN THE MANTELLIAN MUSEUM AT BRIGHTON.*

*(From "Recherches sur les Poissons Fossiles," by M. Agassiz.)*

"Tout le monde sait que le Musée de M. le Dr. Mantell à Brighton est une collection classique pour la cranie, et la formation Veldienne. Les soins minutieux que M. Mantell a donnés depuis bien des années à ces fossiles, les ont rendus plus parfaits que tous ceux des autres musées : car souvent il est parvenu à les detacher entièrement de la roche dans laquelle ils se trouvaient; ou du moins à les produire en relief, en détachant toutes les matières solides qui recouvreraient les parties les mieux conservées de l'animal."

ORDER I.—The *Placoidians*, (from πλαξ, a broad plate.) The skin, covered irregularly with enamelled plates, sometimes of a large size, but frequently in the form of small points, as in the shagreen on the skin of sharks, and the tubercles on the integuments of rays.

* Now in the British Museum.

§ 40.

FISHES OF THE SUSSEX CHALK.

357

PTYCHODUS latissimus. Mantell's South Down Fossils. Tab. xxxii. fig. 19. Agassiz
Poiss. Foss. Vol. iii. tab. 25.

polygyrus. Ibid. Tab. xxxii. figs. 23, 24.

mammillaris. Ibid. Tab. xxxii. figs. 18, 20, 25, 29.

decurrens.

allior. South Down Fossils. Tab. xxxii. figs. 17, 21, 27.

Teeth, and perhaps vertebræ, of the above species, and a few ex-
amples of their dorsal defences, (*Ichthyodorulites* of Dr. Buckland,)
are the only remains hitherto discovered. (*Agass. Poiss. Foss.* Vol.
iii. tab. 10ª, 10ᵇ.) The teeth were referred to fishes of the genus
Diodon, by previous authors, and the defences were called radii, or
fin-bones of balistes, and siluri.

Teeth of a new species of *Ptychodus* (*P. Mortoni*) have been discovered in the sand of New Jersey, United States, by Dr. Morton.—(*Morton's Synopsis*, Pl. 18, figs. 1, 2.)

PTYCHODUS,—*spec. undetermined*. Dorsal defences, and a beautiful example of a fin, are represented in the Fossils of the South Downs. Tab. xxxiv. fig. 8. Tab. xxxix. and Tab. xl. fig. 3.

GALEUS *pristodontus*. South Down Fossils. Tab. xxxii. figs. 12 to 16. Agass. Poiss. Foss. Vol. iii. tab. xxvi. fig. 14.

NOTIDANUS microdon. Agass. Tab. xxxii. fig. 22.

LAMNA *appendiculata*. Agass. Tab. xxxii. figs. 2, 3, 5, 6, 9.
*acuminata*. Agass. Tab. xxxii. fig. 1.

Mantelli. Agass. Tab. xxxii. figs. 4, 7, 8, 10.

crassissima.

ODONTARIS raphiodon.

SPINAX major. Agass. Poiss. Foss. Vol. iii. tab. 10, figs. 8, 14.

PSAMMODUS asper. Poiss. Foss. Vol. iii. tab. 10, figs. 1, 3.

ACRODUS transversus. Poiss. Foss. Vol. iii. tab. 10, figs. 4, 5.

GYRODUS angustus. Poiss. Foss. Vol. ii. tab. 66a, figs. 14, 15.

The above order of fishes is represented by five genera, of which
one, containing twelve species, is extinct. The fishes of the genera
Ptychodus, Galeus, and Lamna, are very widely distributed.

ORDER II.—The *Ganoidians*, (*γανως*, splendour, from the brilliant surface of their enamel.) These are characterized by angular scales, formed of horny or bony plates, protected by a thick layer of enamel, *Lign.* 68, fig. 1, p. 339.

MACROPOMA Mantelli. South Down Fossils. Tab. xxxvii. and xxxviii. Agass. Poiss. Foss. Vol. v. tab. 60ᵇ, fig. 2.

Coprolites of: South Down Fossils. Tab. ix. figs. 5, 11.
Agass. Poiss. Foss. Vol. ii. tab. 65.

The Macropoma is perhaps the most remarkable of all the chalk
fishes; in most examples the membranes of the stomach are pre-
served.

358

THE WONDERS OF GEOLOGY.

LECT. IV.

SPHÆRODUS mammillaris. From Clayton chalk-pit.

DERCETIS elongatus. Lign. 74, page 349. Length 16 inches. South Down Fossils. Tab. xxxiv. figs. 10, 11. Tab. xl. fig. 2. Agass. Poiss. Foss. Vol. ii. tab. 66a, figs. 1 to 8.

The above order comprehends three extinct genera, with three species. Another species of *Dercetis* has been found in the chalk of Westphalia.

### ORDER III.—The *Ctenoïdians*, (κτεις, a comb.)
The scales of this order are pectinated on their posterior margin, like the teeth of a comb, and are composed of laminæ of horn or bone, but have no enamel. *Lign.* 68, *fig.* 4, p. 339.

BERYX Lewesiensis. (B. ornatus of Agassiz.) South Down Fossils. Tab. xxxiv. fig. 6. Tab. xxxv. Tab. xxxvi. Agass. Poiss. Foss. Vol. iv. tab. 14a.

— radians. History of the County of Sussex. Vol. ii. Part ii. p. 15, fig. 22. Agass. Poiss. Foss. Vol. iv. tab. 14b, fig. 7.

— microcephalus. Agass. Poiss. Foss. Vol. iv. tab. 4c, figs. 7 to 9.

There are other species of Beryx in the chalk of Bohemia and Westphalia; and genera nearly related to *Beryx*, in the schist of Glaris.

### ORDER IV.—The *Cycloïdians*, (κυκλος, a circle.)
The scales smooth, with a simple margin, composed of laminæ of horn or bone without enamel. *Lign.* 68, *fig.* 3, p. 339.

OSMEROIDES Mantelli. (Salmo Lewesiensis of Mantell.) South Down Fossils. Tab. xxx. fig. 12. Tab. xxxiv. fig. 3. Tab. xl. fig. 1. Agass. Poiss. Foss. Vol. v. tab. 60º.

To the above species belong the remarkable uncompressed specimens now in the British Museum.

OSMEROIDES Lewesiensis. Agass. Poiss. Foss. Vol. v. tab. 60c. (Salmo? Lewesiensis of Mantell.) This species is more elongated than *O. Mantelli*, and the number of rays in the dorsal fin is greater.

— granulatus. History of Lewes. Vol. i. plate xxix. fig. 13. The bones of the head, with the jaws and teeth, have alone been discovered. Agass. Poiss. Foss. Vol. v.

ENCHODUS halocyon. South Down Fossils. Tab. xxxiii. figs. 2, 3, 4. Tab. xliv. figs. 1, 2. Agass. Poiss. Foss. Vol. v. tab. 25, figs. 11 to 6.

SAUROCEPHALUS lanciformis. (Harlan.) South Down Fossils. Tab. xxxiii. figs. 7, 6. Trans. Geol. Soc. of Pennsylvania, Vol. i. p. 83. Agass. Poiss. Foss. Vol. v. tab. 25, figs. 21 to 29.

SAURODON Leanus. (Hays.) Trans. American Philos. Society, vol. for 1830, plate 16. Agass. Poiss. Foss. Vol. v. tab. 25, figs. 17 to 20.

HYPSONDON Lewesiensis. South Down Fossils. Tab. xxxiii. fig. 8. Tab. xlii. figs. 1 to 5. Agass. Poiss. Foss. Vol. v. tab. 25a.

§ 40.

FISHES OF THE SUSSEX CHALK.

359

From the resemblance of the teeth of this fish to those of reptiles, it
was supposed that the original belonged to an extinct genus of
saurians; but in 1833, a considerable portion of the head, with the
maxillæ, many vertebrae, &c., were discovered in a block of chalk,
near Lewes, and the true characters of this remarkable ichthyolite
determined.

The statement that the teeth of the Saurodon and Saurocephalus
were first ascertained to belong to fishes, and not to reptiles, by the
microscopical observations of Prof. Owen, is not correct, for M. Agassiz
had long previously determined their true characters.

\*\* The following fishes have been named by M. Agassiz, since the
above table was constructed.

ACROGNATHUS *boops*. Lign. 72, page 347. Natural size. Agass. Poiss. Foss. Vol. iii. tab. 60ª, figs. 1, 4. An unique specimen from Southerham quarry, near Lewes.

AULOLEPIS *typus*. Lign. 73, page 348. Length 6 inches. An unique specimen, from Clayton chalk-pit, Sussex. One nearly perfect example has alone been found. Poiss. Foss. Vol. iii. tab. 60, figs. 5, 8.

BELONOSTOMUS *cinctus*. Agass. Poiss. Foss. Vol. ii. tab. 66ª, figs. 10 to 13.

CHIMERA *Agassizii*. Agass. Poiss. Foss. Vol. iii. pl. 40, figs. 3, 5. (Determined by Dr. Buckland.) The beaks or mandibles have alone been discovered.

Mantelli. Lign. 71, page 343. Agass. Poiss. Foss. Vol. iii. Pl. 40, figs. 1, 2. Two mandibles were found, many years since, in a block of chalk, near Lewes. This species also occurs in the Shanklin sand of Kent. A beak has been found by Mr. W. H. Bensted, in the Iguanodon quarry, near Maidstone.

TETRADERUS *minor*. Lewes. Agass. Poiss. Foss. Vol. iii. tab. 60, figs. i. 4.

CATURUS *similis*. Agass. Poiss. Foss. Vol. ii. tab. 66ª, fig. 9.

ACROTEMNUS *faba*. Poiss. Foss. Vol. ii. tab. 66ª, figs. 16, 18.

LECTURE IV.

PART II.

1. Geology of the South-east of England. 2. Geological phenomena between London and Brighton. 3. London and Brighton Railway Sections. 4. The Wealden Formation. 5. Wealden of the Sussex coast. 6. Pounceford. 7. Tilgate Forest. 8. Ripple-marks on Wealden sandstone. 9. Subdivisions and extent of the Wealden. 10. Wealden of the North of Germany. 11. Wealden of the Isle of Wight. 12. Fossil Trees at Brook Point. 13. Wealden of the Isle of Purbeck. 14. Coves in the S. W. of Purbeck. 15. The Isle of Portland. 16. Petrified Forest of the Isle of Portland. 17. Mantellïe. 18. Dirt-bed of the Isle of Purbeck. 19. Organic Remains of the Wealden. 20. Fossil Vegetables. 21. Fossil Cycadeous Plants. 22. Clathraria Lyellii. 23. Fruits of Coniferous Trees. 24. Univalve Shells of the Wealden. 25. Bivalve Shells of the Wealden. 26. Crustaceans of the Wealden. 27. Wealden Insects. 28. Wealden Fishes. 29. Reptiles of the Wealden. 30. Fossil Turtles. 31. Marine Reptiles. 32. Crocodilian Reptiles. 33. Fossil Teeth of Crocodiles. 34. Fossil Crocodile of Swanage. 35. The Dinosaurians. 36. Megalosaurus. 37. Iguanodon. 38. Teeth of the Iguanodon. 39. The Maidstone Iguanodon. 40. Vertebræ of the Iguanodon. 41. Bones of the extremities. 42. Magnitude and proportions of the Iguanodon. 43. The Hylæosaurus. 44. Pterodactyles of the Wealden. 45. Birds of the Wealden. 46. The Country of the Iguanodon. 47. Sequence of Geological changes. 48. Retrospect.

1. GEOLOGY OF THE SOUTH-EAST OF ENGLAND.—From this survey of the marine formation of the Chalk, we turn to the remarkable fluviatile deposits, of which the basin of the cretaceous ocean, in the south-east of England, was composed; in other countries, as I shall hereafter have occasion to remark, that ocean-bed was formed of the Oolite and other more ancient rocks. It will now be necessary to offer a few observations on the geology of the district in which the Wealden is so largely developed.

§ 1. GEOLOGY OF THE SOUTH-EAST OF ENGLAND.

The strata of the south-east of England belong to three
principal groups or formations. The *first* consists of the
*Tertiary* sands, clays, and gravel, described in the previous
Lecture, which occupy depressions in the chalk.

The *second* is the *Chalk*, (including under this term the
White-chalk, Galt, and Greensand,) which forms the most
striking feature in the physical geography of the country.
The upper division of this formation constitutes the South
Downs, which, from the bold promontory of Beachy-head,
traverse the county of Sussex from east to west, and pass
through Hampshire into Surrey; from Godalming the
chalk hills extend by Godstone into Kent, where they are
called the *North Downs*, and terminate in the line of cliffs
that stretches from Dover to Ramsgate. The lowest mem-
ber of the chalk, the *Greensand*, appears as a chain of hills
of irregular elevation, skirting the escarpments of the chalk
downs; the *Galt* occupying the intermediate valley.

The *third* group fills up the area between the North and
South Downs; the most elevated masses form the *Forest-
ridge*, which traverses the district in a direction nearly east
and west, and is composed of alternations of sandstones,
sands, shales, and clays, with a deep valley on each flank,
called the *Weald*: hence the geological designation of the
whole series. From the central ridge of the Wealden, which
varies in height from 400 to 800 feet, and stretches from
Fairlight Down near Hastings on the east, to beyond
Horsham on the west, the strata diverge on each side
towards the Downs, constituting an *anticlinal axis*, and
finally disappear beneath the lowermost beds of greensand.
There are conclusive proofs that the Wealden strata were
originally covered by the chalk, and that their present po-
sition and appearance are attributable to changes which
have taken place subsequently to the cretaceous epoch.*

* See Geology of the South-East of England, chap. xi.

362

THE WONDERS OF GEOLOGY.

LECT. IV.

2. GEOLOGICAL PHENOMENA BETWEEN LONDON AND BRIGHTON.—The direct turnpike roads from London to Brighton pass over the whole series of these deposits, as well as those described in the previous lectures. Proceeding from the Thames, the observer successively traverses the modern silt of the river—the ancient drift and alluvium, containing remains of elephants and other large mammalia—and if he proceeds by Reigate, his road, through Clapham and Tooting, lies over beds of clay and gravel, which are part of the ancient shores of the London basin. At Sutton he ascends the chalk hills of Surrey, and travels along an undulated tract of country, formed by the elevated masses of the ancient cretaceous ocean-bed just described. Arriving at the precipitous southern escarpment of the North Downs, a magnificent landscape, displaying the physical geography of the Weald, and its varied and picturesque scenery, suddenly bursts upon his view. At his feet lies the deep valley of Galt in which Reigate is situated, and immediately beyond the town, appears the elevated ridge of Greensand, which stretching towards the west, attains at Leith Hill an altitude of one thousand feet;* and to the east forms a line of sand-hills, by Godstone and Sevenoaks, through Kent, to the sea-shore. The Forest-ridge of the Wealden occupies the middle region, extending westward towards Horsham, and eastward to Crowborough Hill, its greatest altitude, and thence to Hastings, having on each flank the wealds of Kent and Sussex; while in the remote distance, the smooth and undulated summits of the South Downs appear like masses of grey clouds on the verge of the horizon.

Pursuing his route, the traveller passes through Reigate, along the valley of Galt, and over the Greensand of Cockshut Hill, and arrives at the commencement of the Wealden.

* See my "Memoir on the Geology of the Country seen from the summit of Leith Hill," in Brayley's History of the County of Surrey, published by Mr. Ede, of Dorking.

§ 3. SECTION FROM LONDON TO BRIGHTON.

363

The Weald clay, containing beds of fresh-water limestone, appears at Horley common; and while in the commencement of his journey the roads were made of broken chalkflints, and at Reigate of cherty-sandstone, the materials here chiefly employed are the bluish-grey calcareous rock of the Weald. At Crawley, sand and sandstone appear, and the road is constructed of grit and limestone, containing fluviatile shells, bones, and plants. Crossing Tilgate Forest and Handcross, over a succession of elevated ridges of sandstone, and through clay valleys, produced by the alternations of the strata, he descends from the sandstone ridge at Bolney, near Cuckfield, and again journeys along a district of Weald clay with fresh-water limestone. Greensand, like that of Reigate, reappears at Hickstead, and is succeeded by a tract of Galt; and finally, entering a valley of Chalk-marl, he reaches a defile in the South Downs, through which the road winds its way to Brighton; the traveller having in the course of his journey passed from one chalk range to the other, and crossed over the interventening area formed by the delta of the Wealden.

3. LONDON AND BRIGHTON RAILWAY SECTION.—A similar section is displayed along the line of railway from London to Brighton. Leaving the station at London-bridge, the tertiary clays with their characteristic fossils, are seen from beyond Deptford, by New Cross, Sydenham, &c.; and approaching Croydon, beds of gravel appear, with interspersions of olive-green sand. The valley beyond Croydon, along the side of which the railway proceeds, is a thick bed of gravel resting on the chalk. Beyond the station called Stoats'-nest, is a fine section of the chalk with flint, and the North Downs are traversed by a long tunnel carried through the solid chalk, and emerging near Merstham, where the firestone and marl rise to the surface. The sands and clays of the chalk are passed at the Red Hill, and Godstone stations, and the Wealden clays appear at Horley, and

364

THE WONDERS OF GEOLOGY.

LECT. IV.

are succeeded by shales, limestones, sands, and sandstones, to the Crawley station.

Passing through a long tunnel in the Wealden, we arrive at Balcombe, where laminated sandstone and shale are seen on each side the cutting. The general dip of the strata hitherto passed is to the north-east; but after crossing the deep wealden valley beyond Balcombe, over a magnificent viaduct, the line runs along alternating layers of sands and clays, which dip to the south-west; we have therefore arrived on the southern side of the grand anticlinal axis of the Forest ridge. The wealden strata continue, with the same general inclination, by Hayward's Heath, which is traversed by a tunnel, to beyond St. John's Common, where they disappear beneath the lowermost greensand beds of the chalk formation. The galt, firestone, and marl succeed, and, lastly, the white chalk of the South Downs, at Clayton Hill; through the base of which a long tunnel passes, and emerges on the south of the Downs. The remainder of the line to the Brighton station, runs over, or through, hills and valleys, of the white chalk. Thus this railway passes through two ranges of chalk hills, viz. the North and South Downs, by tunnels; two of greensand, viz. near Red Hill in Surrey, and Hurstperpoint in Sussex; and two principal ridges of wealden, viz. at Balcombe, and Hayward's Heath. If we take a line bearing more to the west; as, for example, from London

§ 4.

THE WEALDEN.

to the southern shores of the Isle of Wight, in Sandown Bay, we shall have the section represented in *Lign.* 78, which exhibits the entire series of the deposits, and their relative position in the south-east of England.

The older tertiary or eocene strata, forming the site of London, are seen occupying a depression of the chalk; the North Downs of Surrey next appear—then the anticlinal ridge of the Wealden—the South Downs of Sussex and Hampshire succeed—covered on the south by the marine tertiary strata of Southampton—then the depression in the strata occupied by the Solent—the north of the Isle of Wight covered by fresh-water and marine eocene deposits—next the vertical chalk range of the Island—and, lastly, the emergence of wealden beds from under the greensand, in Sandown Bay.*

4. THE WEALDEN.—The tertiary basin of London afforded an example of the accumulation of detritus and organic remains in an inland sea;—that of Paris, of marine and fresh-water sediments, deposited in a gulf open to the sea on the one side, and fed by rivers and thermal springs on the other;—the lacustrine formations of Auvergne, of the gradual precipitation of strata in the tranquil waters of lakes;—the cretaceous formation, of the operations which have taken place in the profound abyss of an ocean;—while the series of deposits to which the term *Wealden* is applied, presents the most striking instance of an ancient delta hitherto discovered. Yet strange as it may appear, although these strata occupy the whole area between the North and South Downs—a tract of country traversed daily by hundreds of intelligent persons from the metropolis—their peculiar characters were entirely unknown twenty-five years ago; the whole group being then sup-

* See Geology of the Isle of Wight, p. 74.

366

THE WONDERS OF GEOLOGY.

LECT. IV.

posed by geologists to belong to a series of marine clays
and sands below the chalk.*

Before entering upon the description of these strata,
I would remind you of the effects of rivers, and the nature

* See Conybeare and Phillips's Outlines of the Geology of England and Wales, pp. 140, 155.

Although the shells forming the Sussex marble of the Wealden,
were supposed, so long since as Woodward's time, to be fluviatile
species, yet this point was controverted by many able conchologists;
and few if any other organic remains, had then been obtained from the
strata of the weald. Having for several years diligently collected the
fossils of the chalk, galt, firestone, &c. in the south-east of Sussex, and
around my native South Downs, I was struck with the want of
accordance between them and some specimens of shells, bones, and
plants, I had procured from the quarries, wells, and cuttings made in
the Wealden district; and by degrees, the fluviatile origin of the
deposits forming the area between the greensands of Sussex, Kent,
and Surrey, became manifest. The absence of *ammonites, echinites,
terebratulæ, corals*, and other common and characteristic fossils of the
chalk, in my Wealden collection, was a circumstance that especially
arrested my attention: and the discovery of bones of large terrestrial
reptiles, with trunks and foliage of land plants, and of innumerable
river shells and crustaceans, in the strata of Tilgate Forest—of which
there were not the slightest traces in the cretaceous deposits,—corro-
borated the inferences suggested by my previous observations. In
1822, the Tilgate strata and their peculiar fossils were first described,
and the fluviatile origin of the deposits pointed out, in my Fossils
of the South Downs; chap. vi. p. 37. In June of the same year, I
communicated to the Geological Society of London, an account
of the extension of these strata over the weald, being the result
of my own and Mr. Lyell's observations. In 1827, my Fossils of
Tilgate Forest appeared, containing nearly 200 figures of Wealden
Fossils. As the discovery of the fluviatile character of these deposits
has recently been attributed to other observers, I feel myself called
upon to state thus briefly the history of my humble labours; and to
corroborate it by the following quotations from Professor John Phillips
and Dr. Fitton.

"Until the appearance of Dr. Mantell's works on the Geology of Sussex, the peculiar relations of the sandstones and clays of the interior of Kent, Sussex, and Hampshire, were entirely misunderstood. No one supposed that these immense strata were altogether of a

§ 4.

THE WEALDEN.

367

of modern fluviatile deposits, as explained in a previous
Lecture (p. 56). We found the deltas of rivers to consist
of clay (or indurated mud), alternating with beds of sand
and sandstone (or consolidated sand), and containing leaves,
branches, and trunks of trees, fresh-water shells, works of
art, bones of man, and of land animals, more or less rolled,
—with boulders formed of fragments of rocks, transported
by torrents from the hills, or washed out of the banks by
the streams.

Let us now suppose that by agencies already explained,
a river has disappeared, that the sea also has changed its
place, and that the bed of the river and the delta, have
become dry land; that towns and villages have been built
upon the consolidated fluviatile sediments, and that the
surface is either clothed with turf or forests, or under
cultivation. If sections of the strata were exposed, either
by natural or artificial means, and the bones of men and
animals, with works of art, and remains of plants and shells,
were visible in the clay or sandstone, such appearances
would excite in us no surprise, because we have made our-
selves acquainted with the process by which such deposits
are accumulated. And should an inhabitant of the new
country express his wonder how brittle shells, and delicate
leaves, and bones, had become imbedded in the solid rock ;

peculiar type, and interpolated amid the rest of the marine formations,
as a local fresh-water deposit, of which only very faint traces can be
perceived in other parts of England."—*Professor John Phillips, Ency.
Metropolitana*, p. 631. Art. Geology.

"It was not until the appearance of Dr. Mantell's Illustrations of the Geology of Sussex, in 1822, that the full value of the evidence which this district affords was made to appear. In that valuable work the author clearly showed, that the extraordinary remains which he had discovered in the beds of Tilgate Forest, must have originated in a lake or estuary, and have been the produce of a climate much warmer than that which is now enjoyed in England."—*Dr. Fitton's Geology of Hastings*, p. 14.

368

THE WONDERS OF GEOLOGY.

LECT. IV.

and if when we stated the manner in which those changes
had been effected, he should not only refuse his assent to
our explanation, but insist that the shells, leaves, and bones,
were merely accidental forms of the stone, should we not
feel astonished at his ignorance and prejudice?—yet not a
century since, and such an opinion almost universally pre-
vailed, and is even still entertained by many. And farther,
if our assumed personage admitted that the remains in
question were fossil animals and vegetables, but asserted
that they had been entombed in the strata by a general
deluge which had softened the crust of the earth, and
engulfed in the sediments of its waters the remains of
animated nature—should we not reply, that as such a cata-
strophe must inevitably have mingled together the relics of
animals and vegetables, whether of the land, the rivers, or
the seas—the regular stratification of the materials com-
posing the delta, and the exclusive occurrence of land and
fresh-water productions, were fatal to such a supposition,
and afforded conclusive evidence of the correctness of our
explanation of the phenomena?—it was by such inductions
that the fluviatile nature of the Wealden was established.

5. WEALDEN OF THE SUSSEX COAST.—From the distribution of the Wealden over the south-east of England, instructive sections have been formed between Beachy Head and Dover, by the action of the sea along the coast. From the stupendous cliffs of Beachy Head, the Chalk extends towards Southbourn, where beds of Galt, Firestone, and Greensand, successively emerge, forming the base of the shore, and abounding in characteristic marine fossils. Passing over Pevensey Levels, the boundary of which on the sea-side is obscured by modern shingle, we arrive at Bexhill and Bulverhithe, and find the cliffs composed of laminated sandstones and clays; and those of St. Leonard, of similar strata, more extensively developed: sands and clays separated into very thin laminæ, alternate with

370

THE WONDERS OF GEOLOGY.

LECT. IV.

friable sandstone, was formerly exposed on the sea-shore;
having at a very remote period been separated from the
adjacent cliff. The action of the waves having bleached
the projecting layers of grit, the mass obtained the local
name of "*White rock*" (Lign. 79); but the late improve-
ments at St. Leonard's have removed all traces of this
outlying portion of the Hastings beds.* The nature of the
organic remains which the strata contain will be con-
sidered hereafter.

6. POUNCEFORD.—In the interior of the country, the quarries opened along the ridges formed by the compact grit, afford various instructive sections; and the valleys which are eroded by streams, expose in many places the beds of shales, laminated clays, and limestones. Pounceford, on the estate of the Earl of Ashburnham, on the road to Burwash, in Sussex, presents several highly interesting sections of these deposits. Descending through a defile cut through the Hastings sands, we arrive at the bottom of a deep glen, along which a rapid stream, that bursts out from between the clay-partings, rushes to a distant and lower valley. On each side the vale, openings are made to arrive at a greyish blue limestone abounding in shells, which is employed on the roads, and is also converted into lime for agricultural purposes. Where the stone lies deep, shafts are sunk from the surface, and after the extraction of the limestone, they are deserted and filled up. This spot is highly interesting and picturesque; incrusting springs issue from the limestone beds, and deposit tufa on the mosses, equiseta, and land-shells. Thousands of fossil shells are seen in the clays and shales; and stems of plants, scales of fishes, teeth and bones of reptiles, and other remains, are imbedded in the stone; while the banks where newly exposed, exhibit numberless alternations of

* Geology of the South-East of England, p. 194.

§ 7.

TILGATE FOREST.

371

laminated shales and clays, full of fresh-water shells.* In a visit to this place with my friend Mr. Lyell, in 1831, many new species of shells were found in the bed of the stream, having been washed out of the banks of clay; and we collected teeth of crocodiles, and bones of fresh-water turtles, and of other reptiles. Several species of *Cyclas*, and of *Potamides*, were abundant in the clay (Lign. 97); and a mussel shell, which I named *Mytilus Lyellii*, to commemorate our excursion (Lign. 98, fig. 2), also a fluviatile species, was found in a mass of shale that had fallen into the rivulet.

7. TILGATE FOREST.—As the *grit*, or calciferous sandstone, forms an excellent road-material, the quarries along the principal lines leading from the metropolis to the south-eastern coast, are very numerous; and those spread over the area of Tilgate and St. Leonard’s Forests, were extensively worked some twenty-five years since, when an increased communication between London and Brighton, rendered it alike necessary and profitable, to keep the turnpike roads in the best possible state.

This district may be described as bounded on the west by the London roads leading through Horsham, and on the east by those which pass by Lindfield, and Cuckfield; the Crawley road, as previously mentioned, passing through Tilgate Forest. These localities, particularly the latter, have acquired much celebrity for their organic remains; the quarries in that part of Sussex having been the principal source, whence the specimens figured in my work on the "*Fossils of Tilgate Forest*"† were derived; but every quarry throughout the Forest-range, from Loxwood in Western Sussex, to Hastings, have yielded the peculiar fossils of the wealden, more or less abundantly.

* See Fossils of Tilgate Forest, p. 47. Geology of the South-East of England, p. 22.

† The Fossils of Tilgate Forest, 1 vol. 4to. with plates, 1827.

BB2

372

THE WONDERS OF GEOLOGY.

LECT. IV.

The quarries around Tilgate Forest, where the calciferous grit is worked, present the following section :—

1. *Uppermost.* Loam or clay—from one, to five or six feet in depth; destitute of fossils.

2. Sandstone of various shades of fawn, yellow, and ferruginous colour; in laminæ, or thin layers, occasionally containing organic remains and pebbles; eight feet thick.

3. *Calciferous grit, or Tilgate stone*—a very fine sandstone, formed of sand cemented together by calcareous spar; it occurs in large masses of a concretional form, imbedded in soft sandstone. This grit has evidently been formed by the percolation of water charged with calcareous matter into loose sand; it abounds in bones and teeth of reptiles; stems and leaves of plants; shells, &c.

4. Sandstone, with concretionary masses of grit; and conglomerate formed of rolled pebbles of sandstone, jasper, quartz, rock-crystal, indurated clay, bones and teeth of reptiles, and of fishes; rolled masses of the grit and sandstone are found in this conglomerate; the organic remains which it contains are generally much waterworn.

5. Blue clay and marl—depth unknown.

This is the usual series of strata exposed in the quarries around Cuckfield, Lindfield, Bolney, &c. Near Horsham the fawn-coloured sandstone is more compact, and of a slaty structure. The thin slabs are used for roofing, and the thicker ones for pavements; their surfaces are sometimes deeply furrowed or rippled; an appearance upon which I will here offer a few observations.

8. **RIPPLE-MARKS ON SANDSTONE.**—The furrowed surface of the sandstones and grits which are used for paving in Horsham, Crawley, and other towns and villages on the Forest-ridge, must have attracted the attention of most persons who have travelled from Brighton to London. The appearance of these slabs, is similar to that presented by the sand along the sea-shore at low water, when the ripples occasioned by the receding waves have been deeply impressed; the markings on the stone have arisen from a similar cause. In many instances the surface is so rough,

§ 8.

RIPPLE MARKS ON SANDSTONE.

373

that the stone is employed in stable-yards, where an uneven floor is required, to prevent the feet of animals from slipping in passing over. It sometimes happens that when a large area of a quarry is cleared from the soil which covers it, a most interesting appearance is presented, the whole surface being rippled over like the strand on the sea-shore; and the spectator is struck with the conviction, that he is standing on the sands of some ancient delta, or estuary, now turned into stone. Sometimes the furrows are deep, showing that the water was much agitated, and the ripple strong; in other instances the undulations are gentle, and intersected by cross ripples, proving a change in the direction of the waves. Some slabs are covered by slightly elevated, longitudinal ridges of sand, made up of gentle risings, disposed in a crescent-like manner; these have been produced by the rills which flowed back into the river, at low water. In other examples, the surface is marked by angular ridges irregularly crossing each other, like the fissures in septaria; these have obviously been caused by deposition into crevices produced in sand or mud by desiccation. Many slabs of stone, the smooth, as well as the furrowed varieties, are covered with small, subcylindrical markings, which are the trails formed by vermes, or mollusca; but I have searched in vain for the foot-marks of turtles or other reptiles, whose bones are so abundant in these strata. The frequent occurrence of impressions of the feet of animals on the rippled sandstone of other formations, renders it probable, that sooner or later, the tracks of some of the oviparous quadrupeds of the Wealden, will be discovered on the slabs of Tilgate stone. The deepest furrows have generally a slight coating of bluish clay, charged with minute portions of lignite, and other vegetable matter; an appearance probably caused by the streams from the shore, that flowed over and coated the rippled sand. The phenomena here noticed afford an

374

THE WONDERS OF GEOLOGY.

LECT. IV.

interesting example of the perfect similarity of a natural
process, in periods separated from each other by immense
intervals of time.*

9. SUBDIVISIONS AND EXTENT OF THE WEALDEN.—The Wealden is subdivided into several groups, which are characterized by the lithological nature of the strata, and the prevalence of certain kinds of fossils; but throughout the whole, the fluviatile character of the formation is maintained: in the lowermost part of the series only are there any intrusions of a marine or estuary nature. In fact, it is not possible to conceive an accumulation of sedimentary detritus more purely fluviatile—a delta more free from marine exuviae. Yet foreigners, and even some English geologists, describe it as a fluvio-marine formation; “*un mélange de fossiles marines et d'eau douce.*” †

Although it is not within the scope of these lectures to
enter upon details of stratification, it is necessary to point
out the principal subdivisions of this extensive system of
fresh-water deposits. ‡

1. WEALDEN UPPER CLAYS AND SANDS.—Stiff blue clays, with septaria, argillaceous ironstone, and beds of shelly limestone, called *Sussex or Petworth marble*.

2. TILGATE-GRIT AND HASTINGS-SANDS. — Fawn-coloured sand, and sandstones, with beds of calcareous grit or *Tilgate-stone*, alternating with blue clays and limestones, marls, and lignite.

3. ASHBURNHAM BEDS.—Alternations of clays, shales, and bluish-grey shelly limestones and shales.

4. PURBECK BEDS.—Clays, sandstones, and shelly limestone called *Purbeck marble*. Limestone, with layers of *vegetable mould*, and trunks of trees in a vertical position—the petrified *Forest of Portland*.

* For a particular account of the Wealden strata in the south-east of England, see my Geology of the South-East of England; Fossils of Tilgate Forest; and Geological Excursions round the Isle of Wight, p. 269.

† M. Pictet—Traité Élémentaire de Paléontologie.

‡ Geology of the South-East of England, p. 182.

§ 9.

SUBDIVISIONS OF THE WEALDEN.

375

Such is the assemblage of deposits to which the term Wealden, first employed in this acceptation by Mr. Martin,* is geologically applied. Alternating layers of clays, sands, and limestones, almost wholly composed of fresh-water univalves, and of small bivalves with minute crustaceans, form the upper series. Sand and sandstone, with bands of arenaceous limestones or calciferous grits, shells, and irregular interspersions of lignite, compose the middle group; while in the lowermost, sands, clays, and argillaceous shelly limestones, with small bivalves, again appear. Another series of clays and limestones, characterized by extensive beds of very small univalves, generally in the state of marble (*Purbeck marble*), succeeds; and buried beneath the whole, is a petrified pine-forest, with cycadeous plants; the trees still erect in the soil in which they grew! And in all these deposits, bones of colossal terrestrial reptiles are more or less abundant.

The upper clays and limestones occupy the valleys of the Wealden districts that skirt the inner escarpments of the chalk downs, in Surrey, Kent, and Sussex; the middle group of sands and sandstones, constitutes the Forest ridge of those counties; and the lower series appears in the deep valleys in the east of Sussex, around Battle, Brightling, Burwash, and Ashburnham.

The Purbeck strata, which are distinguished by thick beds of shelly limestone, principally formed of one small species of paludina, appear on the coast of Dorsetshire, in the Island, or more properly the peninsula, whose name they bear. The lowermost deposits of the Wealden, range along the southern shore of the Isle of Purbeck, and crest the northern brow of the Isle of Portland; overlying the oolitic limestones and clays, of which that insular mass of strata is chiefly composed.

* Geology of Western Sussex, by I. P. Martin, Esq.

376

THE WONDERS OF GEOLOGY.

LECT. IV.

The Wealden beds, or rather the lowermost division, the Purbeck, also occur in the vale of Wardour, which is a valley of denudation, in the south of Wiltshire, representing on a small scale that of the south-east of England. In this valley the various members of the chalk occur in their regular order of superposition, resting on clay and Purbeck limestone, and having the Portland stone beneath.*

At Stone in Buckinghamshire, and Swindon in Wiltshire, the oolite is capped by layers of freshwater limestone and marl of the Purbeck series.

In France, on the coast of the Lower Boulonnais, and in the valley of Bray near Beauvais, strata of a like character are observable, in which the Sussex marble (lumachelle-à-palu-dines), and a fern peculiar to the Wealden, have been discovered by M. Graves of Beauvais, to whom I am indebted for specimens. There can be no doubt that this formation originally extended over a much larger area; for the same fossil fern (Lonchopteris Mantelli, Lign. 88) has been found in strata beneath the greensand, in Sweden, by Professor Nillson; who informed me that several of the plants from Tilgate Forest, were analogous to specimens he had collected in the little island of Bornholm, off the Danish coast. Without implicitly relying upon the correctness of all these observations, the Wealden may be estimated as spreading over an area of more than 200 miles in length from west to east, and 220 miles from north-west to south-east; an extent but little exceeding the delta of the Ganges or of the Mississippi, and surpassed by that of the Quorra, which forms a surface of 25,000 square miles, an area equal to half the superficial surface of England.† The total thickness of the Wealden deposits is estimated at 2000 feet, which is four times that of the delta of the Mississippi.

* Dr. Fitton, "On the beds below the Chalk;" Geological Transactions, 1837, p. 424.

† Dr. Fitton.

§ 10. WEALDEN OF THE NORTH OF GERMANY.

377

10. WEALDEN OF THE NORTH OF GERMANY.—In the north of Germany, the Wealden formation has been traced by M. Römer,* and other observers, over a considerable part of Hanover, covering a large area to the north of the Porta Westphalica, including the coal-field of Bückeburg; the impure coal of which resembles our Sussex lignite.† These Wealden deposits lie upon the oolite, and beneath the lowermost beds of greensand; thus occupying the same geological position as their English equivalents; the total thickness of the series is estimated at 800 feet. Numerous characteristic fossils occur throughout these strata; and even the principal subdivisions of the Sussex group have been distinguished.

During the last year, a beautiful work on the Wealden of the north of Germany, was published by Dr. Wilhelm Dunker, (of Cassel,) in which are numerous important additions to the fauna and flora of the country whence the wealden deposits were derived. It contains figures and descriptions of nearly fifty plants, and a still greater number of shells, several fishes, and two new reptiles; the plants are chiefly ferns and cycadeæ.‡

* Versteinerungen des Nord-deutschen Oolithen-Geberges; by Professor Römer: Hanover, 1836. In this work M. Römer enumerates many fossils which distinguish the Ashburnham (der Ashburnham schichte), Hastings (der Hastings sandstein), Tilgate (Tilgat-stein), and Weald clay (der Wëlder-thon), deposits. Cyprides, Paludinæ, Cyrenæ, Cyclades, &c. are mentioned as universally prevailing throughout the series.

† See Fossils of the South Downs, p. 34.

‡ Monographie der Nord-deutschen Wealdenbildung. Ein Beitrag zur Geognosie und Naturgeschichte der Vorwelt. Von Dr. Wilhelm Dunker. Brunswick, 1846. One vol. 4to. with twenty-one plates. This beautiful volume will of course find its way into the library of every geologist; but I would also strongly recommend it to the intelligent collector of organic remains, on account of the numerous and excellent figures of Wealden plants, shells, &c. The work may be obtained through M. Bailliere, Foreign Bookseller, Regent-street.

378

THE WONDERS OF GEOLOGY.

LECT. IV.

11. WEALDEN OF THE ISLE OF WIGHT.—Freshwater deposits similar to those we have described in Kent, Sussex, and Surrey, appear at the back, or along the southern shore, of the Isle of Wight; constituting the lowermost strata in that island, as shown in the section, *Lign.* 78, p. 364. These strata consist of clays, sands, and sandstones, with bands of shelly limestones, and grit; and are replete with the same species of river shells, terrestrial plants, and bones of reptiles, as the wealden of the S. E. of England. They form a line of low cliffs, in Sandown Bay, on the south-east of the island; and in the bay between Atherfield Point and Compton Bay, on the south-west.*

The relative position of the strata is shown in the annexed section, from the coast at Brook Point, to the chalk downs on the north. If we proceed from the sea-shore at Brook-chine, through the village of Brook, towards Shal-

LIGN. 80.—SECTION FROM BROOK POINT TO SHALCOMB DOWN; IN THE ISLE OF WIGHT.

1. Wealden beds. 2. Fossil Trees. 3. Lower group of Greensand.

4. Galt. 5. Firestone. 6. White Chalk.

comb-down, we pass over the beds in the following order.

1. Wealden clays, grits, &c. forming the cliff. 2 and 3. Greensand. 4. Galt. 5. Firestone. 6. Chalk.

* The reader is referred to my Geological Excursions round the Isle of Wight, for particular information on these strata, and their organic remains.

§ 12.

WEALDEN OF THE ISLE OF WIGHT.

379

The Wealden beds form the entire cliff for several miles along this part of the coast; but they may be seen dipping under the lowermost sands of the cretaceous formation, near Compton-chine on the west of Brook Bay, and Atherfield Point on the east. Most of the peculiar fossils of the Wealden have been obtained from these shores; quantities of bones of enormous reptiles, freshwater shells, and crustaceans in immense quantities; river mussels of large size; and ferns and cycadous plants. But the most remarkable phenomenon at Brook Point, is the occurrence at the foot of the cliff, of a prostrate forest of petrified pine-trees.

12. FOSSIL TREES OF THE WEALDEN, AT BROOK POINT.
—The cliff at Brook Point is between thirty and forty feet high, and is capped by a thick bed of alluvial gravel and loam. It is composed of layers of clay and shale finely laminated, with thin seams and masses of lignite. The lower part of the cliff consists of beds of hard sandstone grit, resting upon mottled clays and sands, which are the lowermost wealden strata in the island. The fossil trees are imbedded in the sandstone, and protrude from the waterworn edges of the rock. This indurated grit forms a sort of buttress at the foot of the cliff, having resisted the tidal action which has carried away the upper and less coherent deposits: the numerous reefs that appear off the shore at low water, and render this coast so dangerous to mariners, have originated from this cause.

The trees are lying confusedly one upon another. There are no erect trunks, nor any other indications that the forest was submerged while growing in its native soil, like that of the Isle of Portland; on the contrary, the appearance both of the trunks in the sand-rock, and of those exposed to view by the removal of the materials in which they were originally imbedded, is that presented by the rafts that float down the great rivers of America; as for example the Ohio and Mississippi. Such rafts entangle in

380

THE WONDERS OF GEOLOGY.

LECT. IV.

their course the remains of animals and plants that may
happen to lie in the bed of the river, and at length subside
and are engulfed in silt and sand; in like manner the fossil
trees in this cliff are associated with river shells (*Uniones*),
and bones of land reptiles. The fossil forest at Brook
Point is, in fact, a raft of pine trees, which floated down
the river that deposited the Wealden beds, and was sub-
merged in its delta, burying with it bones of terrestrial
animals, freshwater mussels, &c.

The trees when lying in the sandstone are invariably
covered with their bark, now in the state of lignite, and
which varies from one to three or four inches in thickness,
according to the magnitude of the trunk. This carbonized
cortical investment is quickly removed on exposure to the
action of the waves; but the ligneous structure, the woody
fibre, remains. The trees are calcareous, not siliceous like
those of Portland; they are more or less traversed by
pyrites, and the delicate veins and filaments of this mineral
which permeate the woody fibre, impart a beautiful appear-
ance to polished specimens. The trunks are generally of
considerable magnitude, being from one to three feet in
diameter; some are of such a size as to indicate a height
of forty or fifty feet when entire. In the conversion of
the bark into lignite, and in the smooth condition of the
trunks, the trees of this fossil forest present a remarkable
dissimilarity from those of the Isle of Portland, which we
shall presently examine; for in the latter the carbonized
bark rarely, if ever, occurs, and the surface of the stems is
similar to that exhibited by the trunks of old decorticated
trees, that have been much weathered by alternate exposure
to air and moisture. At Brook Point, on the other hand,
the trees appear to have been engulfed when fresh and vi-
gorous, with their bark and vessels full of sap. The annular
lines of growth are often very distinct, and I have traced
from thirty to forty on some of the stems; but these circles

§ 13.

WEALDEN OF THE ISLE OF PURBECK.

are unequal, and indicate therefore a variation from year to year in the climate of the country in which they grew. The wood exhibits, under the microscope, the coniferous structure seen in the *Araucaria* (Norfolk Island Pine), the rows of glands or ducts being placed alternately; and the appearance is similar to that of the fossil wood of Willingdon in Sussex.* I observed no traces of the foliage or fruit of these trees, with the exception of a small cone, scarcely so large as that of the larch.† In the strata that overlie the fossil forest, thin interrupted seams and irregular masses of lignite, more or less impregnated with and permeated by iron pyrites, are very abundant.

13. WEALDEN OF THE ISLE OF PURBECK.—The Wealden deposits are next seen in the Isle of Purbeck, the south-eastern part of Dorsetshire, which is distant about fifteen miles across the Channel, from the western extremity of the Isle of Wight. This island is an irregular oval area, between thirteen and fourteen miles in length, and seven in average breadth, from north to south. It consists of cretaceous, wealden, and oolitic strata, which occur in their natural order of succession, but highly inclined, in the section exposed in Swanage Bay, on the east of the island.‡ In this line of coast the geological structure of the Isle of Purbeck is clearly displayed. In Studland Bay, which is to the north of Swanage, the white chalk is seen to emerge from beneath the eocene strata, and form the cliffs; rising up into the range of downs that traverses the island from the east to the south-western shore. The curious flexures produced on the beds of chalk and flint by the elevations to which they have been subjected, are remarkably distinct at

* Medals of Creation, vol. i. p. 160.

† An account of the fossil bones, plants, &c. of the Wealden, which have been discovered along the coast in Brook and Brixton Bays, will be found in Excursions round the Isle of Wight, chap. x. and xi.

‡ Ibid. chap. xii.

382

THE WONDERS OF GEOLOGY.

LECT. IV.

Handfast Point. The lower divisions of the chalk dipping at a considerable angle to the north, next appear; and are followed by the Wealden clays, sands, &c. which stretch

along Swanage Bay, to the elevated ridge of Purbeck strata, on the south of the little town of Swanage. At Durlstone Head a fine section of the Purbeck beds is exposed; and at the extreme point, the Portland oolitic limestone appears. Purbeck has long been celebrated for its quarries, which have been worked from time immemorial, and particularly during the middle ages; the compact varieties of the limestone, which take a good polish, having, under the name of Purbeck marble, been in great request for the religious edifices of that period; and there is scarcely a cathedral or ancient church in England that does not contain columns, sepulchral monuments, or pavements, of this material. This marble (*Lign.* 96) is a congeries of small river snail shells, intermixed with the crustaceous cases of minute cyprides.

14. COVES IN THE SOUTH-WEST OF THE ISLE OF PURBECK.—On the south-west coast of the Isle of Purbeck, the range of vertical chalk strata, the eastern extremity of which forms the high cliffs at Handfast Point (*Lign.* 81), reappears in several coves or inland recesses, which have been formed by the inroads of the sea; no less than nine sections of the strata, from the

1. Firestone. 2. Galt. 3. Greensand. 4. Wealden. 5. Purbeck strata. 6. Portland Oolite.

§ 15.

THE ISLE OF PORTLAND.

383

chalk to the oolite inclusive, being exposed along this coast, within a distance of five miles.* The subjoined diagram (Lign. 82) will explain the geological structure of these bays.

LIGN. 82.—PLAN OF THE COVES ON THE SOUTH-WEST COAST OF THE ISLE OF PURBECK.

a, Chalk. b, Firestone. c, Galt. d, Greensand. e, Wealden. f, Purbeck beds. g, Portland stone.

The northern barrier of the coves consists of precipitous chalk cliffs; the entrance is formed by rocks of Portland and Purbeck limestone; and between them is a low tract composed of the less durable wealden strata. These bays expose, in fact, transverse sections of the range of hills formed by the Portland and Purbeck beds; and of the clays, sands, &c. of the Wealden; and, at their back, precipices of great height, produced by the destruction of the southern face of the vertical chalk of the Downs.

Thus, within the distance of six or seven hundred yards, we may examine the entire series of strata, from the Chalk to the Portland oolite, by proceeding from the inland cliffs to the southern extremity of the bays; the section of the east side of Lulworth Cove (Lign. 83) shows the relative position of the formations.

15. THE ISLE OF PORTLAND.—The island, or peninsula, of Portland, is a bold headland, off Weymouth, about four miles and a half in length, two in breadth, and

* Geol. Exc. Isle of Wight, p. 368—389.

384

THE WONDERS OF GEOLOGY.

LECT. IV.

300 feet high; it is united to the main land by a bank of shingle called the Chesil beach. It presents, on the north, a precipitous escarpment, and declining towards the south, appears, on approaching it from the east or west, like

an insulated inclined plane, rising abruptly from the sea. The southern extremity is flanked by low calcareous cliffs, which, from the constant action of the sea, are worn into hollows and caverns. The base of the island is formed of a blue clay (*Kimmeridge clay*), surmounted by beds of sand; and on these are superimposed thick strata of the oolitic limestone, known as the *Portland stone*, which is extensively quarried in the northern brow of the island.

The strata dip to the south at an angle which corresponds with the profile of the island. The coasts are steep, the base of Kimmeridge clay forming a talus, surmounted by perpendicular crags of oolite. The southern extremity consists of low oolitic limestone cliffs, which are worn into numerous caverns by the force of the waves.

The northern brow of the island, to a depth of upwards of twenty feet, is formed of finely laminated fresh-water limestone, locally termed “*The Cap*,” which belongs to the Purbeck system, and is superimposed on the

uppermost bed of oolite. The Kimmeridge clay, which is the lowest visible deposit in the island, contains the usual marine shells, &c. that prevail in this bed in the Isle of

§ 16.

THE ISLE OF PORTLAND.

385

Purbeck,* and other parts of England. The oolitic lime-
stone, which lies immediately upon the clay, contains
nodules and veins of flint and chert. The middle group
is full of the usual oolitic shells; and the upper series, to
within twenty feet of the surface, consists of the fine archi-
tectural stone which is locally termed the *white-bed*. Upon
this is a stratum, three or four feet thick, of limestone, full
of cavities left by numerous shells, of which the casts only
remain; and above is an irregular layer of flint nodules,
in coarse oolite, which is covered by a thin bed of earthy
detritus.

16. THE PETRIFIED FOREST OF PORTLAND.—The freshwater strata which form the northern brow of the Isle of Portland, belong to the lowermost beds of the Purbeck group of the Wealden formation. They are in fact the first sediments that were deposited by the body of fresh water, which covered for ages the ancient oolitic rocks; and they indicate the commencement of the delta, which ultimately spread over a great part of England and northern Germany; they are therefore, in every point of view, in the highest degree interesting. The annexed section of a quarry (*Lign.* 84) in which these strata are seen in their natural position, will serve to exemplify the following remarks.

The lowermost beds in this quarry consist of the Portland
building stone (8); and upon these are layers of rubbly
oolite (7), covered by a thin seam of black earth, with
interspersed vegetable matter, in which fossil cycadeous
plants have been discovered. This is succeeded by lami-
nated freshwater limestone (5), upon which is the remark-
able stratum, called " *Dirt-bed*" (4), by the quarrymen.
This bed is about one foot in thickness, and consists of a
dark brown friable loam, containing a large proportion of
earthy lignite, and like the modern soil of the Island, many

* Geol. Exc. Isle of Wight, p. 401.

C C

§ 17.

FOSSIL CYCADEÆ OF PORTLAND.

387

vegetation, there being but few trees or shrubs in the
whole Island.

But the most remarkable fact which this section pre-
sents, is the position of the trees and plants in the Dirt-bed;
for they are still erect, as if they had been petrified while
growing in their native forests, with their roots in the vege-
table soil, and their trunks extending into the limestone
above (Lign. 84, 4, 3,). As the Portland building stone lies
beneath the freshwater strata, which are but little employed
for economical purposes, the petrified trees are removed,
and thrown by as rubbish. On one of my visits to the
island (in the summer of 1832), the surface of a large area
of the dirt-bed was cleared, preparatory to its removal, and
the appearance presented was most striking. The floor of
the quarry was literally strewn with fossil wood, and before
me was a petrified forest, the trees and the plants, like the
inhabitants of the city in Arabian story, being converted
into stone, yet still remaining in the places which they
occupied when alive ! Some of the trunks were surrounded
by a conical mound of calcareous earth, which had evidently,
when in the state of mud, accumulated round the stems and
roots. The upright trunks were generally a few feet apart,
and but three or four feet high; their summits were broken
and splintered, as if they had been snapped or wrenched off
by a hurricane at a short distance from the ground. Some
were two feet in diameter, and the united fragments of one
of the prostrate trunks indicated a total length of from
30 to 40 feet; in many specimens portions of the branches
remained attached to the stem. In the *Dirt-bed*, there were
numerous trunks lying prostrate, and fragments of branches.

The external surface of all the trees I examined was
weatherworn, and resembled that of posts and timbers of
groins or piers within reach of the tides, and subjected to the
alternate influence of the water and atmosphere; there are
but seldom any vestiges of the bark.

17. FOSSIL CYCADEÆ:—MANTELLIA.—The fossil plants

CC 2

388

THE WONDERS OF GEOLOGY.

LECT. IV.

related to the recent *Cycas and Zamia*,* occur in the intervals between the pine-trees; and the dirt-bed is so little consolidated, that I dug up with a spade, as from a parterre, several specimens that were standing on the very spot where they originally grew, having, like the columns of the Temple of Puzzuoli (p. 107), preserved their original

LIGN. 85.—SILICIFIED TRUNK OF MANTELLIA NIDIFORMIS, FROM PORTLAND; one-fourth the natural size.

(Cycadites megalophyllus, Dr. Buckland.)

a, Central mass of cellular tissue; b, Circle of radiating woody plates;

c, Zone of cellular tissue; d, The case, or false bark.

erect position, amidst all the revolutions which have subsequently swept over the surface of the earth, and buried them beneath the accumulated detritus of innumerable ages.

These fossil plants, though related to the recent Cycadæ,

* These plants are so common in conservatories that their general appearance must be familiar to the reader. In the botanic gardens at Kew, there are magnificent specimens of Cycas and Zamia, and of other plants of hot-climates, of which related forms occur in the Wealden.

§ 18.

DIRT-BED OF PURBECK.

belong to a distinct genus.* There are two species; one is short, and of a spheroidal form (*M. nidiformis*, Lign. 85); the other is longer, and subcylindrical (*M. cylindrica*†).

The trees and plants are completely silicified; and their internal structure is beautifully preserved in many examples; the wood, microscopically examined, displays the organization of the Araucaria. A cone has been found in the Dirt-bed, which Dr. Brown considers to be nearly related to the fruit of the Norfolk Island pine (*Araucaria excelsa*). The Portland and Isle of Wight fossil trees, appear to belong to the same species of coniferæ.

LIGN. 86.—SECTION OF THE CLIFF ON THE EAST OF LULWORTH COVE. 1, Purbeck calcareous slate; 2, Dirt-bed, with trunks of trees; 3, Oolitic limestone of Portland.

18. DIRT-BED OF PURBECK.—The Dirt-bed extends through the northern part of the Isle of Portland, and appears on the coast of Purbeck under circumstances of peculiar interest. In the highly inclined strata of the cliff, about a furlong to the east of Lulworth Cove, a considerable number of petrified trees is exposed, under similar conditions with those of the Portland quarries. The lowermost strata (Lign. 86, 3), are the Portland oolitic

* Named by M. Adolphe Brongniart, *Mantellia*.

† Specimens of the former species are called “Crows’ nests” by the quarrymen; who believe them to be birds’ nests, originally built by crows in the pine-trees, and which have since become petrified.

390

THE WONDERS OF GEOLOGY.

LECT. IV.

limestones, full of marine shells; upon these is the dirt-bed with fossil trees (2); this is covered by cream-coloured calcareous stone in thin undulated laminæ, locally termed “soft-burr” (1); and above are shales and narrow bands of limestone, belonging to the lower series of the Purbeck.

The dirt-bed has been discovered by Dr. Buckland near Thame in Oxfordshire; and by Dr. Fitton, in the Vale of Wardour. It also occurs at Swindon in Wiltshire on the top of the Portland oolite, where fossil coniferous wood is found in abundance, and a few examples of Mantellia have been obtained. Between Stone and Hartwell in Buckinghamshire, a seam of carbonaceous earth occupies the geological position of the Portland dirt-bed, and is covered by cream-coloured marls and limestones resembling the *Cap*, in which wings of insects, and leaflets of Wealden ferns, with remains of very small fishes, have been discovered.*

From what has been stated, it is evident, that after the marine strata forming the base of the Isle of Portland were deposited at the bottom of a deep sea, and had become consolidated, the bed of that ocean was elevated above the level of the waters, and constituted an island, or archipelago, covered with pine forests, and cycadous plants. How long this new country existed, cannot be ascertained, but that it flourished for a considerable period is certain, from the number and magnitude of the petrified trees.†

* See History of Fossil Insects in the secondary rocks of England, by the Rev. P. B. Brodie.

† *Modern submerged Forest.*—An interesting modern example of the subsidence of a considerable tract of country clothed with forests, the trees remaining erect, although submerged beneath a river which still flows over them, is described by a late American writer, and will serve to illustrate the remarks in the text. The whole district, from the Rocky Mountains on the east and the Pacific Ocean on the west, and from Queen Charlotte's Island on the north to California on the south, presents one vast tract of volcanic formation. Basalt—both

§ 19.

ORGANIC REMAINS OF THE WEALDEN.

391

19. ORGANIC REMAINS OF THE WEALDEN.—The fossils of the Wealden consist of leaves, stems and branches of plants of a tropical character; bones of enormous terrestrial reptiles of extinct genera, and of turtles, flying reptiles, and birds; remains of fishes of several genera and species; and numerous fluviatile shells and crustaceans.

The bones are, for the most part, broken and rolled, as if they had been transported from a distance. They are more or less impregnated with iron, and commonly of a dark brown colour. Those in loose sand and sandstone are often porous and friable; those in the Tilgate grit, heavy, brittle, and with the internal structure well preserved; in fractured portions imbedded in the limestone, the interstices are filled with white calcareous spar, and the cancellated structure of the bones is frequently permeated by the same substance.

The fossil vegetables occur either bitumenized, or in the state of sandstone casts; carbonized leaves and twigs are abundant in some of the strata, and the stems and branches are sometimes silicified.

columnar and in amorphous masses, veins and dykes—every where occurs, and craters of extinct volcanoes are still visible. Elevations and dislocations of the strata have taken place on an immense scale; and successive beds of basalt, amygdaloidal trap, and breccia, prove the alternation of igneous action and periods of repose. Within a few miles of the cascades of the river Columbia, and extending upwards of twenty miles, trees are seen standing in their natural position, in a depth of water from twenty to thirty feet. The trees reach to high, or fresh-water mark, which is fifteen feet above the lowest level of the tide; but they do not project beyond the freshet rise, above which their tops are decayed and gone. In many places the trees are so numerous, that “we had to pick our way with the cance, as through a forest. The water of the river was so clear, that the position of the trees could be distinctly seen down to their spreading roots, and they are standing as in their natural state, before the country had become submerged. Their undisturbed position proves that the subsidence must have taken place in a tranquil manner.”—*Journal of an Exploring Tour beyond the Rocky Mountains*, by the Rev. Samuel Parker, A.M. New York. 1838.

392

THE WONDERS OF GEOLOGY.

LECT. IV.

The shells in the clays have undergone but little change, and in many examples, the epidermis and even ligament are preserved; in the limestones, the substance of the shells is converted into spathose carbonate of lime; in the sandstones, casts of the interior of the shells are often the only vestiges. With these general remarks, I pass to the consideration of the fauna and flora of the Wealden epoch.

20. FOSSIL VEGETABLES.—From the abundance of carbonized vegetable remains in many of the laminated shales and clays, and the occurrence of *lignite*, or brown-coal, in masses and layers, which sometimes alternate with shales abounding in fresh-water bivalves, a striking analogy is presented to some of the divisions of the *Coal measures*; but there are no beds of coal of any economical value in the English Wealden.* In Hanover, however, this formation contains an extensive coal field, which furnishes excellent fuel.

But notwithstanding the prevalence of vegetable matter in the strata, specimens exhibiting the internal structure of the plants, with any tolerable distinctness, are very rare; and though my researches were for many years unremitting, I have obtained but few fossil plants that admit of satisfactory conclusions as to the organization and affinities of the originals. I shall restrict my observations to a brief account of the principal kinds, and the circumstances under which they occur.

*Ferns.*—Entire layers of the calciferous grit of Tilgate Forest are so full of minute portions of carbonaceous matter,† as to present a dark mottled colour; and upon examining the imbedded particles, they prove to be the detritus of plants ground to pieces by agitation in water loaded with sand and mud. Specimens in my possession

* See Geology of the South-East of England, p. xviii.; and Fossils of the South Downs, p. 35, for an account of an unsuccessful trial for coal at Bexhill.
† Fossils of Tilgate Forest, Plate 3, fig. 6.

§ 20.

FOSSIL PLANTS OF THE WEALDEN.

393

show that they have been principally derived from two
elegant extinct species of ferns, which are peculiar to the
Wealden. The one is characterized by its slender and
minutely divided wedge-shaped
leaflets (Sphenopteris Mantelli,
Lign. 87); the other by the
distribution of the nervures
or veins (Lonchopteris Man-
telli, Lign. 88), the long and
many times pinnated leaves,
and the reticulated disposition
of the secondary veins that
spring from the mid-rib of the
leaflets. This plant has also
been found in the valley of
Bray, in the lower Boulonnais,
by M. Graves of Beauvais (p.
227); and in Sweden, in strata
supposed to be of the same epoch as the wealden. The Lon-

LIGN. 87.—SPHENOPTERIS MAN-
TELLI. TILGATE FOREST.

LIGN. 88.—LONCHOPTERIS MANTELLI. TILGATE FOREST.

chopteris likewise occurs high up in the greensand strata,
at Atherfield and Shanklin chine in the Isle of Wight.*

* It was first noticed in this geological position by Mr. John Morris.
Geol. Exc. Isle of Wight, p. 230.

394

THE WONDERS OF GEOLOGY.

LECT. IV.

These ferns probably did not attain a considerable magnitude. The largest stem of the *Sphenopteris* I have seen,

must have belonged to a plant about five or six feet high. Several other species of ferns are associated with these remains; but the two plants above named, constitute by far the greatest proportion of the fossil vegetables of Tilgate Forest. I have a remarkable specimen of another fern, in which the parts of fructification are beautifully preserved (*Lign. 89*); the same species has been found in the Wealden of the north of Germany.* Obscure indications of other species of ferns occur in our wealden clays, but no intelligible specimens have been obtained. In the German deposits Dr. Dunker has discovered upwards of twenty species.†

Leaves of Cycadeous plants, and seed-vessels of *Restiaceæ*, are met with in the ironstone of Heathfield, Sussex; and remains of the foliage of trees allied to the Cypress and Juniper. The stems of a species of *Equisetum* (*mare's tail*) abound in the blue limestone of Pounceford.‡

21. CYCADEOUS PLANTS.—*Endogenites erosa*.§—In the strata of Tilgate Forest, in the sands of Hastings,

1.

2.

LIGN. 89.—FROND OF A FERN IN FRUCTIFICATION; IN SANDSTONE, FROM TILGATE FOREST.

*(Alethopteris elegans; of Dr. Dunker.)*

Fig. 1. Three pinnules magnified.

Fig. 2. The specimen of the natural size.

* Monographie der Nord-deutschen Wealdenbildung, Pl. VII. fig. 7.

† Ibid. p. 28.

‡ *Equisetum Lyellii*; Med. Creat. vol. i. p. 108.

§ Fossils of Tilgate Forest, Pl. III. III*.

§ 22.

CLATHRARIA LYELLII.

395

and in the clays of Germany,* many specimens of the stems of a very curious plant, formerly supposed to be related to the *Euphorbia*, or *Cacti*, have been discovered. These stems are of various forms; some are cylindrical, and tapering at both ends; others are flattened, and of a clavated shape. The constituent substance is a grey, compact, subcrystalline sandstone, and the external surface of the stems is traversed by fine meandering grooves, and deep tubular furrows, lined with minute quartz crystals; a transverse section exhibits the surface covered by small pores, and a few large openings, the sections of the tubes. In a specimen which I picked up on the beach at Brook Point, bundles of vascular tissue are preserved; these are disposed in a flexuous zone round the margin of the stem. The plant is supposed by Dr. Brown to be allied to the Cycadeæ.† Cones and stems of a species of Zamia have been found with bones of the Iguanodon in Sandown Bay.‡

22. CLATHRARIA LYELLII (*Ligns. 92, 93*).—The most interesting plant belonging to this tribe of coniferæ, of which any vestiges have been found in the Wealden, is that first discovered by me in Sussex, and described under the name of *Clathraria Lyellii*.§

The fossil remains consist of portions of the stem, scored by the imprints left by the attachment of the petioles; leaf-stalks; the internal axis; and obscure indications of the foliage and seeds. || The stem is composed of an axis, having the surface covered with reticulated fibres; and of a false bark, produced by the union of the consolidated bases of the petioles, the insertions of which are rhomboidal and transverse.

* Mon. Nord. Weald. Tab. III.

† See Geology of the Isle of Wight, p. 288.

‡ Medals of Creation, vol. i. p. 160.

§ Fossils of Tilgate Forest, Pl. I. II. and III. and Geol. of the S. E. of England, Pl. I.

|| Medals of Creation, vol. i. p. 182.

398

THE WONDERS OF GEOLOGY.

LECT. IV.

naturally. Similar characters are observable in the petioles
of the recent Zamiæ;\* the presence of this characteristic
plant of the Wealden so high up in the chalk formation is
in accordance with the occurrence of bones of the Iguanodon,
&c. in the greensand of Kent, which we shall notice
hereafter.

In the strata of Tilgate Forest, the Clathrariæ are inva-

riably associated with waterworn
bones of reptiles, pebbles, gravel,
and other drift; and are often
imbedded in the fluviatile con-
glomerate which is found in
some parts of the Wealden. They
appear to have floated down the
river with the carcasses and
limbs of the reptiles, and at
length to have sunk to the
bottom, and become imbedded in
the mud of the delta.

A cluster of petioles belonging to a large plant of the Clathraria, has recently been discovered in the greensand near Maidstone; in the same quarry of Kentish-rag in which were found, some years since, a considerable portion of the skeleton of an Iguanodon, associated with drifted coniferous wood, and other vegetable remains. I have collected a few detached petioles of Clathraria from the chalk marl, and white chalk, near Lewes.

23. FRUITS OF CONIFERÆ.—The seed-vessels of several coniferous trees and plants have been discovered in the Wealden, but under circumstances which render it impos-

\* In a flourishing old plant of the *Encephalartus pungens* from South Africa, in the botanic gardens at Kew, all the lower part of the stem, beneath the coronet of foliage, is covered with persistent petioles; those which have borne leaves have vascular pits on the summit, but the abortive petioles are smooth and entire at the apex.

LIGN. 92.—A PETIOLE OF CLA-
THRARIA LYELLII; from the
stem of the specimen figured
Lign. 91.

a, The external surface; b, the in-
ternal surface; c, the vascular
markings, left on the summit
by the separation of the leaf.

400

THE WONDERS OF GEOLOGY.

LECT. IV.

The specimen from Sussex, *fig. 4*, is remarkable for the double prominences on the scales. I extracted a small cone from the lignite beds at Brook Cliff, which may possibly be the fruit of the pine-trees of the fossil forest in that locality: a cone resembling that of the Norfolk Island Pine has been found in the dirt-bed of Portland.

Four small carpolithes, and leaves of nine or ten (supposed) species of cycadous plants, are described and figured by Dr. Dunker, from the Wealden of Germany.*

24. **UNIVALVE SHELLS OF THE WEALDEN.**—The durable remains of molluscous animals are most abundant; thick beds of limestone, spread over wide areas, and chiefly composed of but three or four species of bivalves and univalves, being a constant character of this group of deposits. The prevalent shells belong to a few common fresh-water forms, as *Paludina*, *Cyclas*, *Unio*; three or four other fluviatile, and an equal number of marine genera, the latter being very sparingly distributed, make up the conchology of the Wealden. Of the *Cyclas*, a fresh-water bivalve which we have already noticed as abounding in certain tertiary strata, upwards of forty species have been determined: of the *Unio*, a well-known fluviatile mussel, ten or twelve species: and of the river snails, the *Paludinæ*, a like number. It is worthy of remark, that of the common lacustrine snails, the *Limnæa*, so abundant in the fresh-water tertiary beds of the Isle of Wight, but one wealden species is known; and of the *Planorbis*, its constant associate in those deposits, and in our ponds and lakes, one only has been detected.† The conchological fauna of the Wealden is, in fact, rigidly fluviatile. In some parts of the lower beds, layers of oysters occur, and occasionally a stray marine

* Mon. Nord. Weald. Tab. II. IV. VII. pp. 16, 21.

† Ibid. Tab. X. figs. 1, 2. *Planorbis Inglesi* and *Limnæa Hennei*,
*Wealden*

§ 24.

SHELLS OF THE WEALDEN.

401

shell is found entangled in the fresh-water sediments; but, I repeat, the shells hitherto discovered afford no grounds for invalidating my original statement,* that the Wealden is an ancient delta—a fluviatile formation.

The most abundant shells of this division of testaceous mollusca are the *Paludinæ*, of which the Sussex and Pur-

LIGN. 94.—UNIVALVE SHELLS OF THE WEALDEN.

Fig. 1. Paludina Sussexiensis. 2. Melanopsis.

3. Neritina Fittoni; a, natural size.

beck marbles are almost wholly made up: the former limestone differing from the latter, simply in the species of which it is composed.

The Sussex marble is a congeries of paludinæ; chiefly of *Paludina fluviorum* and *P. Sussexiensis* (Lign. 94, fig. 1.). In the coarse varieties of this stone, the shells are decomposed, and the interstices left by their removal filled up with clay; but in the compact layers and blocks, the shells are transmuted into calcareous spar, and their cavities contain indurated marl and limestone, of various shades of grey, blue, yellow, &c. interspersed with pure white, mottled with black; the polished slabs (Lign. 95) display innumerable sections of the inclosed shells, and rival in interest and beauty many of the foreign marbles. The black and dark brown spots and veins in this and other shelly marbles, have originated from the transmutation of the soft bodies of the mollusca into a carbonaceous

* In 1822.

D D

402

THE WONDERS OF GEOLOGY.

LECT. IV.

substance, termed *molluskite*.\* The shells, which were empty at the period of their becoming imbedded, had their

LIGN. 95.—POLISHED SLAB OF SUSSEX MARBLE.
(Composed of Paludinus and Cyprides.)

cavities filled with mud, silt, or other detritus, which has subsequently hardened into clay, marl, limestone, &c.: but those which contained the gelatinous bodies of the snails, are occupied by a mass consisting of carbon, and a large proportion of phosphate of lime. In the polished sections of the marble, this carbonaceous animal matter often appears in black or dark brown spots and veins: and the most beautiful slabs owe their variegated appearance to the contrast produced by the molluskite with the white calcareous spar. Upon examining thin slices of this marble under a slightly magnifying power, many of the shells, and the interstices between them, are seen to be filled up with the cases of *Cyprides* (Lign. 98).

\* See Medals of Creation, vol. i. p. 431. Geology of the Isle of Wight, p. 248.

§ 25.

PURBECK MARBLE.

403

The Purbeck marble differs from that above described,
in being composed of smaller shells of the same genus

(Paludina elongata); it
also contains abundance
of cyprides; and in some
layers, small bivalves
(Uniones), replaced by
white spar, give a va-
riety to the markings
exposed in the sections.
The polished cluster-
columns in the Temple

LIGN. 96.—POLISHED SLAB OF PURBECK
MARBLE.

(Composed of a small species of Paludina.)

Church in London, and in Chichester Cathedral, and
many of the monuments in Westminster Abbey, are
of this marble; in other words, they are constructed of
conglomerated masses of petrified shells of snails, which
lived and died in the rivers that flowed through a country
inhabited by the Iguanodon and other extinct colossal
reptiles, ages before a single layer of the chalk was
deposited!

A few species of an elongated spiral freshwater univalve (*Melanopsis*), are found in great perfection in some of the clays at Pounceford (*Lign. 97, a*), associated with the characteristic bivalves of the wealden (*Lign. 97, b and c*). A few specimens of a small elegant Nerite (*Neritina Fittoni, Lign. 94, fig. 3*), have been found in the calciferous grit of Tilgate Forest and Hastings.

25. BIVALVE SHELLS.—We have already had occasion to
observe that many kinds of the bluish grey limestones of
the Wealden, are largely composed of small bivalves of the
genera *Cyclas* and *Cyrena*; some layers form a compact
marble that will bear a good polish. In the clay the shells
are often beautifully preserved; as in these specimens from
Pounceford (*Lign. 97*), in which the epidermis and liga-
ment remain.

DD 2

404

THE WONDERS OF GEOLOGY.

LECT. IV.

The fresh-water mussels called *Uniones*, from their solid pearly shells, occur in considerable abundance in some of

LIGN. 97.—WEALDEN SHELLS, FROM POUNCEFORD, SUSSEX.
*a*, Melanopsis tricarinata; *b*, Cyclas media; *c*, Cyclas membranacea.

the Wealden strata, but the species are, for the most part, of small size. But I discovered, not long since, a remarkably fine and large Unio, in the cliff at Brook Point, imbedded with the fossil trees (*ante*, p. 379). I have named it *Unio Valdensis*, or Wealden mussel. These shells are from four to six inches long, and well preserved; the surface is of a tawny red colour, the horny ligament, with its transverse rugæ remains, and in some examples the shells are occupied by the body of the animal in the state of molluskite.† The collocation of these large mussels with the drifted trees and bones of terrestrial reptiles, in strata so manifestly of fluviatile origin, completes the analogy between the rafts imbedded in the delta of the wealden,

* This shell is the Potamides carbonarius of Römer, and is abundant in weald clay at Neurladt, in Hanover.

† See Geology of the Isle of Wight, p. 303, for the description, and Pl. VI. fig. 1, for a figure of this fine fossil shell, which resembles some of the Uniones of the American rivers. Also the London Journal of Geology; Plate XIV.

§ 26.

CRUSTACEANS OF THE WEALDEN.

405

and those brought down, and engulfed in mud and sand,
by the Ohio and Mississippi, and other large rivers.

1

2

3

LIGN. 98.—CRUSTACEANS AND SHELL, FROM THE WEALDEN.

Figs. 1 and 3. Cypris granulosa; highly magnified.

2. Mytilus Lyellii; one-third natural size.

A few small freshwater mussels occur in the clay at Pounceford, associated with cyclades; a species is figured in *Lign.* 98, fig. 2.

26. CRUSTACEANS OF THE WEALDEN.*—The crustaceans of the Wealden, though occurring in inconceivable numbers, belong to but two kinds; viz. *Archæoniscus* and *Cypris*. The first are referable to the isopodous order, of which our common *Oniscus*, or wood-louse, is an example; but the fossil *Isopoda* were aquatic. They were discovered by Mr. Brodie, with remains of insects, in grey marly Purbeck limestone, near Dinton.†

The Cyprides are very small crustaceans, having the body inclosed in a horny bivalve shell or case, united by a hinge, and admitting the antennæ and feet to protrude and be at liberty, when the case is open. They have only one eye, situated in the middle of the head; the species which abound in our pools of fresh-water have two pairs of pats or feet; those of brackish and salt-water (*Cytherina*) have three pairs, and inferior antennæ; but the shells are so alike, that the lacus-

* Medals of Creation, vol. ii. p. 544.

† Ibid. p. 542; and History of Insects, p. 10.

406

THE WONDERS OF GEOLOGY.

LECT. IV.

trine and marine forms cannot be distinguished in a fossil state: the nature of the originals can only be inferred by the organic remains with which they are collocated. Like other crustaceans they frequently shed their cases, and the mud spread over the bottoms of still lakes is often covered with their exuviae. The largest living Cypris does not exceed one sixth of an inch in length. In a fossil state their cases appear like white elliptical reniform scales, on the surface of the recently separated laminæ of clay, shale, and limestone. Upon exposure to the air the cases decompose, and leave the surface of the shale or stone covered with the casts of the shells, which appear as minute polished tubercles; some layers of the indurated ironstone have a granulated surface from these remains.* In the Sussex and Purbeck marbles, as previously mentioned, the cyprides are most abundant. There are several fossil species, one of which is represented very highly magnified in Lign. 98, figs. 1, 3.

As the recent species inhabit either still lakes or gently flowing streams, and not the turbulent waters of estuaries, it follows that sediments largely charged with these exuviae, associated with freshwater shells, afford strong presump- tive evidence of a fluviatile origin.

27. INSECTS OF THE WEALDEN.—The durable nature of the wing-cases (*elytra*), legs, antennæ, &c. of the co- leoptera, and other insects, rendered it probable that some vestiges of this class of articulated animals would be pre- served in the muddy sediments of the Wealden. But I sought in vain for any vestiges of this kind, in the localities of the south-east of England that were accessible to my observations. In the remote outliers of the Purbeck beds in the vale of Wardour in Wilts, and in several places in

* In the sandstone quarries at Langton Green, near Tunbridge Wells, slabs of this kind occur, studded over with casts of cyprides, and minute uniones.

§ 28.

INSECTS OF THE WEALDEN.

407

Buckinghamshire, the researches of the Rev. P. B. Brodie have been most successful, and the acumen and perseverance of that gentleman have brought to light several hundred specimens of insects or parts of insects. These consist chiefly of remains of *Coleopterous*, *Orthopterous*, and *Hemipterous* insects; and several kinds of *Diptera* and *Neuroptera*. I have subsequently collected a few relics of beetles from the Wealden marls at Wateringbury near Maidstone; and of coleoptera, diptera, and some unknown forms, from near Stone in Buckinghamshire; a locality of fossil insects first pointed out by Mr. Brodie.

The Wealden insects hitherto discovered are of very small size, especially the Diptera and Coleoptera; and if any inferences could be legitimately drawn from these limited observations, a low climatorial temperature of the country they inhabited would be indicated, as the magnitude of the insect tribes is in proportion to the heat of the climate. The insects discovered by Mr. Brodie, and described and figured by Mr. Westwood, comprise species of *Aphis*, cuckoo-spit insects (*Cercopidæ*), diamond beetles (*Curculionidæ*), terrestrial Crickets, Cockroaches, and Dragonflies (*Libellulæ*); of the latter, which are inhabitants of the water in their first stage, and of the air in their last, there are relics belonging to species of gigantic size. As a general result, Mr. Westwood considers the entomological fauna of the Wealden to indicate a temperate climate.* At the same time we must remark, that it is not at all probable that the annulosa of the wealden epoch are wholly represented by the minute and fragmentary remains at present known.

28. FISHES OF THE WEALDEN.—The fishes whose relics are distributed throughout the Wealden formation

* From Mr. Westwood's observations, in the elegant volume entitled, A History of the Fossil Insects of the Secondary Rocks of England, by the Rev. P. B. Brodie; one vol. 8vo. 10 plates. Van Voorst, 1845.

408

THE WONDERS OF GEOLOGY.

LECT. IV.

are, for the most part, either of the shark family, or of
related genera; and of species allied to the large river-pikes
of South America. Detached scales, teeth, dorsal rays, and
bones of these fishes are very abundant; but it is rarely
that united portions, either of the skeleton, or of the dermal
covering, are preserved.

Strong thick enamelled scales, bearing a high polish and
having two processes of attachment, with small hemi-
spherical teeth, called by the workmen *fishes' eyes*, are the

LIGN. 99.—RESTORED OUTLINE OF THE LEPIDOTUS OF THE WEALDEN.

(By M. Agassiz.)

most common relics of this kind.* They belong to the
*Lepidotus*, or bony pike, a genus of which a living repre-
sentative inhabits the rivers of South America. In the
grits and conglomerates of Tilgate Forest, and of Hastings,
these scales and teeth are in prodigious numbers. A few
tolerably perfect specimens of the fishes from which these
teeth and scales were derived have been obtained, and have
enabled M. Agassiz to determine the form of the original
*Lign.* 99).† In the Purbeck strata a small species of
*Lepidotus* is equally abundant.

* Medals of Creation, vol. ii. p. 637.

† A specimen in the British Museum (from my collection) has a considerable part of the cranium and body, with the dorsal and pectoral fins. Another (discovered by Robert Trotter, Esq. formerly of Borde Hill, Sussex) retains a mass of the scales in juxtaposition, more than a foot wide, near where the caudal fin commences; this fish must therefore have been ten or twelve feet long, and three feet wide.

§ 29.

FISHES OF THE WEALDEN.

409

Finely striated tricuspid teeth, and others of a transversely elongated shape, with a sharp elevated central cusp and several small lateral ones, are the next in frequency. These belong to fishes termed *Hybodonts*, allied to the sharks, from which they did not materially differ in their habits and economy. They possessed two dorsal spines or rays, and remains of these appendages are occasionally met with in the Tilgate grit and Hastings sandstone.*

I have found in the Tilgate grit a few small oblong teeth, with the surface of the crown covered by fine radiating striæ; these are referable to another genus of squaloid fishes (*Acrodus*†), related to the Port-Jackson shark.

Small palatine bones, having a median row of flat transversely arched dental plates, with two rows of hemispherical obtuse teeth on the sides, are occasionally found in the quarries around Tilgate Forest, Horsham, and Hastings. These belong to fishes of the genus *Pycnodus*, so named from the thickness of their teeth, which are constructed for crushing hard substances. I have not observed any other determinable parts of these fishes.‡

Two very small fishes, belonging to the genus *Leptolepis*, and two others equally minute, which are supposed to indicate new generic characters, were discovered by Mr. Brodie, in the strata containing insects, near Dinton, in the Vale of Wardour.§

29. REPTILES OF THE WEALDEN.—It will doubtless surprise the reader to learn that the whole of the enormous bones and teeth before us, are those of reptiles,|| and that

* Medals of Creation, vol. ii. p. 607, 621. Fossils of Tilgate Forest, Pl. V. fig 14; Pl. XV. fig. 2.

† Medals of Creation, vol. ii. p. 614.

‡ Ibid. p. 641.

§ History of Fossil Insects, Pl. I. figs. 1, 2, 3, 4; p. 15.

|| This Lecture was illustrated by several hundred specimens of bones and teeth of reptiles from the Wealden; many of such magnitude, that the assemblage resembled an accumulation of the dissevered skeletons of gigantic elephants or mastodons.

410

THE WONDERS OF GEOLOGY.

LECT. IV.

not a vestige of any of the mammalia occurs in the Wealden deposits. Even these teeth, which so strikingly resemble the incisors of the Rhinoceros, and these bones of the feet and toes, which are so similar in shape and size to those of the Hippopotamus, belong to oviparous quadrupeds. Many of the specimens can be referred to certain extinct forms of saurians, or lizards; but the affinities of others have not been ascertained. The determination of these fossil bones is indeed no easy task; for while in many marine deposits, considerable portions of the skeletons, or even the entire series, are often discovered, in the Wealden, with but few exceptions, every bone, tooth, and scale, has been found apart from each other; and as if to render the task still more perplexing, the relics of several different species and genera are scattered at random through the rocks. Every specimen, too, bears evidence of having been transported from a distance. It would seem as if the limbs and carcasses of the animals had floated down the stream, and been rolled backwards and forwards by the tides, and the bones broken, before they sank down and became imbedded in the mud of the delta. To collect these scattered fragments, and extricate them from the solid rock—to reunite them into a whole, and assign to each skeleton of the respective animals, the bones which once belonged to it, yet not to confound the different species together—such is the labour which the comparative anatomist has to perform, who undertakes to investigate the nature of the wealden saurians. I reserve for the next Lecture some general observations on the economy and habits of reptiles, and will now describe the fossil relics before us.

30. TURTLES OF THE WEALDEN.—The bones and plates of chelonian reptiles are very common in the Purbeck limestone, and in the grit, sandstone, and shale of Tilgate Forest. They are referable to two or more freshwater, and one marine species; one of the former appears to belong

§ 30.

TURTLES OF THE WEALDEN.

411

to an *Emys*, or freshwater turtle, described by Cuvier,* as occurring in the Jura limestone at Soleure. It is a very flat species, and probably attained two feet in length.

Many ribs and other parts of the carapace of a *Tri-onyx* have been discovered in the shale of Pounceford, and grit of Tilgate Forest; the external surface of the dorsal plates is shagreened all over, as is usual in these chelonians, which have no shelly covering, but only a thick, tough skin, or integument; the recent species inhabit the Nile and Euphrates.

*Trionyx Bakewelli.* Among these remains of fresh-water turtles are costal and dorsal plates, and other bones of a chelonian reptile, which, in its essential characters, is closely allied to the *Trionyces*, but differs from all known recent species, in having possessed a horny dermal integument formed of plates of tortoise-shell. This is indicated by the fossil ribs, which not only have a shagreen or punctated surface, like those of the recent species, but also imprints of the horny scutes or scales.† Except in having a defensive coating of tortoise-shell, this turtle must have closely re-sembled the existing predaceous, soft, fresh-water chelos-nians; and doubtless, like those reptiles, inhabited the muddy beds of rivers and lakes; preying upon the eggs and young of the larger reptiles, and on the mussels and other fluviatile mollusca, whose shells are commonly associ-ated with its remains.‡

*Chelonia Bellii.* A considerable portion of the carapace

* Oss. Foss. tom. v. p. 232.

† See Medals of Creation, vol. ii. p. 777.

‡ I discovered remains of this species, and pointed out their pecu-liar characters, more than twenty-five years since. The specific name is to commemorate the important services rendered to British Geology by my late respected friend, Robert Bakewell, Esq., author of the best "*Introduction to Geology*," in this or any other language. See my Fossils of Tilgate Forest, p. 60, Pl. VI. fig. 1; and Geology of the South-East of England, p. 225.

412

THE WONDERS OF GEOLOGY.

LECT. IV.

and plastron of a true marine turtle, belonging to a species three feet in length, was obtained from the sandstone of Tilgate Forest many years since, and some fragments are figured in my early works on the fossils of that district.*

31. MARINE REPTILES OF THE WEALDEN.—By far the greater part of the bones obtained from the quarries of Tilgate Forest, Horsham, &c. belong to colossal terrestrial reptiles; but with these are associated the osseous remains of two or three genera, which there is every reason to suppose were inhabitants of the sea into which the river flowed, that deposited the strata of the Wealden.

*Plesiosaurus*. I have collected from various Sussex localities, bones of the extremities and cervical and caudal vertebræ, of one or more species of the extraordinary marine reptile called *Plesiosaurus*, whose remains are found in such prodigious quantities in the Lias and Oolite;† thus, we have proof that this animal was at least an occasional visitant of the bays and estuaries of the Wealden river.

*Cetiosaurus*.‡ Some of the largest vertebræ and bones found in the Wealden strata belong to an aquatic reptile, probably of marine habits, of which numerous bones occur in the oolite of Oxfordshire, Northamptonshire, &c. The vertebræ are distinguished by their nearly circular faces, and relatively short bodies; in the dorsal the anterior face is nearly flat, and the posterior concave; but in the caudal both are concave, with a well-defined border, which gives the body a deeply excavated character. Some specimens

* Medals of Creation, vol. ii. p. 776. Fossils of Tilgate Forest, Pl. VII. fig. 2.

† Fossils of Tilgate Forest, Pl. IX. figs. 4, 5.

‡ The name implies the affinity of these reptiles to the cetaceans. See Medals of Creation, vol. ii. p. 726. No vestiges of true cetaceans have been found in a fossil state in strata older than the tertiary; it would seem that the advent of the terrestrial and aquatic mammalia on our globe, took place contemporaneously.

§ 32.

CROCODILIAN REPTILES.

413

are eight inches in the transverse diameter of the articular face, and but four and a half in the antero-posterior length of the body of the vertebræ.*

These reptiles must have rivalled the living Whales in bulk, for some specimens indicate a length of forty or fifty feet; they are supposed to have had web-feet, and a broad vertical tail.† The bones found in the Wealden may have been transported from the sea by the tide, or the living animals may have occasionally been carried far up the river, as is sometimes the case with the modern cetaceans.

32. CROCODILIAN REPTILES OF THE WEALDEN.‡—The loricated or mailed saurian reptiles, as the Alligators, Crocodiles, and Gavials, of which numerous remains occur in the eocene strata, are well known as the largest existing forms of oviparous quadrupeds.

No relics of any living species have been observed in the secondary strata, but several allied genera appear to have flourished during these epochs. But the crocodilians of these ancient types differed materially in structure from the modern; and particularly in the vertebral column, which in one fossil genus only is composed of concavo-convex vertebræ, and these are in a reversed position; the ball or convexity of the bone being directed forwards, or anteriorly, instead of in the contrary direction, or posteriorly, as is the case in the living Crocodiles.

As a general character, it may be stated that the crocodilians with broad muzzles, as the Cayman and Alligator, do not occur in a fossil state below the eocene deposits; all the reptilian remains of that family in the secondary forma-

* I discovered a fine suite of four consecutive vertebræ in the sandstone of Tilgate Forest, and succeeded in extricating them entire from the rock. One of these vertebræ is figured in Philos. Trans. for 1841, Pl. IX. fig. 13.

† British Association Reports, 1841, p. 102.

‡ Medals of Creation, p. 718.

414

THE WONDERS OF GEOLOGY.

LECT. IV.

tions, belong to the division with elongated beaks or muzzles, like the Gavial of the Ganges.

*Streptospondylus.*\* The bones, and jaws with teeth, of the crocodilian reptiles to which this name (signifying reversed spine) has been applied, were first discovered in the Oolitic clays of Honfleur and Havre; the vertebræ are united by a ball and socket joint; the convexity or ball being anterior, instead of posterior as in the living crocodiles. Several large vertebræ of these reptiles have been obtained from the sandstone and grit of Tilgate Forest, and from the clays in Brook Bay, in the Isle of Wight.

33. FOSSIL TEETH OF CROCODILIAN REPTILES.—The teeth of the Crocodile are very numerous; they are of a conical form, and consist of a succession of cones, like a series of thimbles, of various sizes, fitted into each other; they are striated externally, and have a prominent lateral ridge; as the outer tooth wears away, a new one is ready to supply its place; the teeth of the old Crocodile are

LIGN. 100.—TOOTH OF CROCODILIAN REPTILE: FROM TILGATE FOREST; natural size.
(Goniopholis crassidens.)

therefore as fresh as those of the young animal but just escaped from the egg. The interior of the teeth is never

\* Medals of Creation, vol. ii. p. 725.

§ 34.

SWANAGE FOSSIL CROCODILE.

415

completely filled up; hence, at whatever age a tooth may
be removed, there is found, either in the socket, or in the
cavity of the tooth itself, a new germ, in a greater or less
state of advancement, ready to occupy the place of the old
one, when the latter shall be removed; and this succession
is often repeated. In this fossil tooth (*Lign.* 100) from
Tilgate Forest, the internal series of cones is exposed, in
consequence of the removal of the outer case of the old
tooth. Numerous fossil teeth, possessing this character,
have been obtained from the wealden; they are separable
into two kinds.

The first is from an inch to two inches in length, of a
slender acuminated form, laterally compressed, and gently
recurved, with a thin edge in front and behind; resembling
in appearance a tooth of the Megalosaurus (*Lign.* 101),
with the serrated edges worn off.* Some biconcave ver-
tebræ, with compressed wedge-shaped centres,† are supposed
to belong to the same reptile, which has been named *Sucho-
saurus cultridens*.‡ The other form of tooth has a cylin-
drical base, and an obtusely conical crown with numerous
longitudinal grooves and ridges, and a sharp line on each
side; a specimen, attached to a small block of sandstone,
is represented *Lign.* 100.§

34. SWANAGE FOSSIL CROCODILE. — The teeth last de-
scribed are comparatively of frequent occurrence in the
wealden of the south-east of England, and are often
associated with dermal, or skin-bones, which are the
osseous supports of the thick horny scutes or scales of the
integument of mail, with which the Gavials and other

* Medals of Creation, vol. i. Pl. VI. fig. 7. Fossils of Tilgate Forest, Pl. V. fig. 10.

† Fossils of Tilgate Forest, Pl. IX. fig. 11.

‡ British Association Reports for 1841, p. 68.

§ Medals of Creation, vol. i. Pl. VI. fig. 5. Fossils of Tilgate Forest, Pl. V. figs. 1, 2, 9.

416

THE WONDERS OF GEOLOGY.

LECT. IV.

crocodilians are covered;* and certain extinct reptiles
appear to have had these scutes even more largely deve-
loped. As the fossil teeth and dermal bones were commonly
associated together, I was led to suppose that they might
belong to the same species; an opinion which was con-
firmed a few years since, by the discovery, in the Isle of
Purbeck, of a considerable portion of the skeleton of a
Crocodile, with similar teeth and dermal appendages.

In the summer of 1837, the workmen employed in a
quarry in the immediate vicinity of Swanage, had occasion
to split asunder a large block of the Purbeck limestone,
when, to their surprise, they perceived many bones and
teeth on the surfaces they had just exposed. As this was
no ordinary occurrence—for though scales of fishes, shells,
&c. were frequently observed in the stone, bones had never
before been noticed—both slabs were carefully preserved
by the proprietor of the quarry; and fortunately my intel-
ligent friend, Robert Trotter, Esq. happening to visit
Swanage a short time afterwards, heard of the discovery,
and with that liberality and ardour for the advancement
of science for which he is distinguished, obtained the spe-
cimens, and presented them to me. I cleared away the
stone, so far as the brittle state of the bones would permit
without injury, and they are now two of the most interest-
ing groups of crocodilian remains that have been discovered
in this country.†

On one of the slabs, a considerable portion of the left side

* See Medals of Creation, vol. ii. p. 701.

† Both the slabs of the Swanage specimen are now placed side by side in a case in the British Museum; in the same room with the remains of the Iguanodon and other fossil saurians. There can be no doubt that the entire lower jaw of this reptile might have been obtained, if the quarrymen had taken the precaution of examining the adjoining block of stone. In the same case are several teeth and dermal bones of this species from Tilgate Forest.

§ 34.

SWANAGE FOSSIL CROCODILE

417

of the lower jaw, with two teeth in place, is preserved; and many detached teeth and dermal bones are distributed over the stone. There are numerous ribs and biconcave vertebræ, the latter having an irregular medullary cavity in the centre of the body; the chevron bones are of the same form as in the Gavial. The bones of the pelvic arch, and several of those belonging to the extremities, remain.

The dermal scutes are flat; their width, which is equal throughout, is about one-third of the length. They are of various sizes, from three to six inches long. The inner surface is smooth, and the external covered with irregular deep pits or hollows; some round, others angular. These differ from all known recent and fossil dermal bones, in having a lateral projection which fits into a corresponding depression on the under surface of the opposite angle of the adjoining scute.* Numerous hexagonal and pentagonal scutes, articulated together by marginal sutures, also entered into the composition of the osseous dermal cuirass; this reptile must, therefore, have possessed a flexible and impenetrable coat of mail, capable of affording protection against the attack of any assailant.†

*Macrorhyncus Myeri.* The cranium of another reptile of the Gavial type, has been found in the wealden of Germany, and is figured in Dr. Dunker's beautiful work; it is characterized, as the name implies, by its extremely elongated snout.‡

*Poecilopleuron.* Vertebræ and other bones of a crocodilian reptile, related to the *Goniopholis*, are occasionally found in the wealden deposits of Tilgate Forest and the Isle of Wight, associated with the remains of that

* Medals of Creation, vol. ii. p. 702.

† Teeth of the Swanage Crocodile or *Goniopholis* have been found in the wealden of Germany, by Dr. Dunker; see Mon. Nord. Weald. Pl. XX. fig. C.

‡ Mon. Nord. Weald. Tab. XX.

E E

418

THE WONDERS OF GEOLOGY.

LECT. IV.

animal. The vertebræ are biconcave, and have a large medullary cavity in the middle of the centrum of the bone, which is often filled up with white calcareous spar. The body of the vertebra is contracted in the middle, the neural arch anchylosed with no trace of suture, and the spinous process is remarkable for its backward inclination.*

*Raphiosaurus?* Professor Owen states, in his report on the British fossil reptiles, that no vertebræ of the true crocodilian type, that is, with the anterior surface concave, and the posterior face convex, have been found in strata below the chalk. I have, however, discovered in the sandstone of Tilgate Forest, several small vertebræ of this kind, which closely resemble in their proportions those of the small lizard of the chalk, the *Rhaphiosaurus* (*ante*, p. 354).†

* The remains of this reptile were first described by M. Deslongchamps, (under the name of *Poecilopleuron*,) from specimens discovered in the Oolite near Calne, in Normandy. See British Association Report for 1841, p. 84; Fossils of Tilgate Forest, Pl. IX. fig. 8, represents a caudal vertebra.

† *On a peculiarity of structure in the first caudal vertebra of the adult Gavial.* — The discovery of the Swanage crocodile induced me to institute a rigorous examination of the skeletons of the recent Gavials in the museum of my friend Dr. Grant, of the London University, with the view of determining the affinities of the fossil remains. In the course of my investigation I detected a peculiar conformation in the *first caudal* or *coccygeal* vertebra of the recent gavial, which, strange to say, appears to have escaped the notice of previous observers. The vertebræ of the existing crocodilian family are invariably concave in front, and convex behind; but the *first caudal* (Lign. 100,* 3) in the adult Gavial is *doubly convex*; and the last sacral vertebra (2) *concave posteriorly*, to receive the anterior convexity or ball of the caudal. These peculiarities are shown in the annexed sketch.

The last *cervical* vertebra in Turtles and Tortoises has a similar structure. In a very young Gavial in Dr. Grant's collection, the sacrococcygeal surfaces are as flat as in the vertebræ of mammalia; while in the Crocodile and Alligator, of the same early period, the coccygeal vertebra is convex in front, as in the adult gavial. This mechanism

§ 35.

DINOSAURIANS.

419

35. DINOSAURIANS.*—We now arrive at the consideration of three genera of extinct saurians or lizards, the Megalosaurus, Iguanodon, and Hylæosaurus, which are so essentially different in their osteological characters from all other known types, as to constitute a distinct order, that unites the lacertian with the crocodilian oviparous quadrupeds. The remains of these animals are principally distributed in the Wealden deposits; but of the first, the most interesting relics have been obtained from the Stonesfield slate, which is situated in the lower division of the Oolite; and of the

confers the power of free motion without risk of dislocation or mutation. The importance of a knowledge of this fact to the palæontologist is too obvious to require remark; the discovery in the wealden of a caudal vertebra, having both the extremities convex, would, I must confess, have been very perplexing, previously to my detection of this peculiarity of structure in the recent Gavial.

LIGN. 100.*—SACRAL AND CAUDAL VERTEBRÆ OF THE GAVIAL.

Figs. 1. 2. The two anchylosed sacral vertebrae. 3. The first caudal or coccygeal vertebra, which is doubly convex.

* Dinosaurians, signifying fearfully great Lizards; a term employed by Professor Owen to designate an order of extinct terrestrial reptiles, which comprises the Iguanodon, Megalosaurus, and Hylæosaurus. It is to be regretted that some other name was not chosen; for the occurrence of the same word (*δεινός*, *deinos*) in Dinosaurium (*ante*, p. 173), Dinornis (*ante*, p. 129), &c. suggests to the unscientific reader, an erroneous idea of an affinity between these extinct reptiles, mammals, and birds, which it was desirable to avoid.

E E 2

420

THE WONDERS OF GEOLOGY.

LECT. IV.

second, a considerable portion of the skeleton has been
found in the greensand of the chalk formation.*

These genera comprehend the colossal crocodile-lizards
of the dry land of the secondary epochs. The long bones
of the extremities of the two first are of colossal pro-
portions, and have large medullary cavities, with well
developed processes; their metacarpal, metatarsal and
digital bones, with the exception of the ungueal phalanges,
(bones which support the nails or claws,) resemble those of
the Hippopotamus, and other large pachydermal mammalia.†
A very remarkable peculiarity in the osteological cha-
racters of this order consists in the sacrum being made
up of five vertebræ, anchylosed together into a solid
column; whereas in all other saurians, it is formed of but
two united vertebræ; and this is accompanied by another
modification, for the neural arches of the vertebræ are shifted
to the interspaces between the bodies of those bones, and
thus great solidity is given to the pelvic arch. Both these
arrangements have an evident relation to the great size of
the hinder extremities of these reptiles, and the enormous
carcass they had to support.

From the great magnitude of some of the bones, these
fossils have excited the curiosity even of the common
observer; and although an exaggerated idea has been
generally entertained of the size of the original animals,
yet even when their assumed proportions are reduced
to their natural dimensions by the rigorous formulæ of the
comparative anatomist, they are sufficiently colossal to
satisfy the most enthusiastic lover of the marvellous. Of
this the reader may be easily convinced, if he will visit the

* See Medals of Creation, vol. ii. p. 729.

† See Medals of Creation, chap. xviii. for a concise view of the osteological characters of these reptiles: and Professor Owen's Report on Fossil Reptiles in the Transactions of the British Association of Science, for 1841, for a full consideration of the subject.

422

THE WONDERS OF GEOLOGY.

LECT. IV.

apparently to the same species (*M. Bucklandi*) as that of Stonesfield. The tooth of this reptile (*Lign. 101*) is distinguishable by its sabre-like form, conical laterally compressed crown, and finely serrated trenchant edges. From this structure of the tooth it may be inferred that the Megalosaurus was carnivorous; its length is estimated at nearly thirty feet.

37. THE IGUANODON.*—Soon after my first discovery of remains of large vertebrated animals in the strata of Tilgate Forest, some teeth of a very remarkable character particularly engaged my attention, from their dissimilarity to any that had previously come under my notice. Even the quarrymen, who had been accustomed to collect the teeth of fishes and other relics of that nature, had not observed them, until shown three or four mutilated specimens, which I had extricated from a block of stone on the road-side. Attention having thus been directed to the subject, additional examples were soon discovered; and at length I obtained a series of teeth in various conditions, from the pointed unused tooth of the young reptile (*Lign. 102, fig. 2*), to the obtuse, worn, flat crown of the adult (*Lign. 104*). From the resemblance in the form of the perfect tooth to that of the Iguana,† a terrestrial lizard of

* Medals of Creation, vol. ii. p. 739. Brit. Assoc. Reports for 1841, p. 120.

† The Iguanas are land lizards, which inhabit many parts of America and the West Indies, and are rarely met with north or south of the tropics. They are from three to five feet in length, and feed on insects and vegetables, climbing trees, and chipping off the tender shoots. They nestle in the hollows of rocks, and deposit their eggs, which are like those of turtles, in the sands or banks of rivers. The Iguana is furnished with a row of very small, closely-set, pointed teeth, with serrated edges, which have no distinct alveoli or sockets, but are attached at the base, and by the outer surfaces of the fangs to the jaw; the alveolar process forms an external parapet, but there is no internal bony covering. The new teeth do not, as in the croco-

§ 37.

THE IGUANODON.

423

the West Indies, I proposed the name of *Iguanodon* (signi-
fying an animal with teeth like the Iguana), for the extinct
reptile to which they belonged.*

The numerous bones and teeth subsequently exhumed
from the strata of Tilgate Forest, Horsham, Battle, Hast-
ings, and other places in Sussex, and in the Isle of Wight;†
and of a considerable portion of the skeleton of an indi-
vidual discovered in the greensand of Kent, have supplied
the data upon which our present knowledge of the characters
of the original is based. But unfortunately the form and
structure of the skull are still unknown; and of the jaws,
a fragment retaining the fangs of a few teeth, is the only
recognizable relic.

38. TEETH OF THE IGUANODON.‡—The first specimen
which arrested my attention was a portion of a large tooth
which, from the flat surface of the crown, had evidently
belonged to a herbivorous animal; for it possessed the
prismatic form of a worn incisor of one of the large pachy-

dile, spring up in the centre of the cavities of the old, and push
through them, but arise from near the inner part of the base, and by
pressure occasion the absorption of a portion of the fang of the old
tooth, which they ultimately displace, by destroying the adhesion to
the dental parapet. The teeth of the Iguana closely resemble the
perfect fossil tooth, (Lign. 102, fig. 2,) in form, but not in structure or
size; those of the recent lizard scarcely exceeding in magnitude the
teeth of the common mouse. In the Iguana the crown of the tooth
never presents a flat surface; it is broken or chipped off by use, but
not ground smooth as in the herbivora. The reason is obvious; none
of the existing reptiles are furnished with cheeks or moveable cover-
ings to their jaws, and therefore cannot perform mastication; their
food or prey is seized by the teeth and tongue, and swallowed
whole.

* See my memoir "On the teeth of the Iguanodon, a newly discovered fossil herbivorous reptile, from the strata of Tilgate Forest." Philos. Trans. for 1825.

† Geology of the Isle of Wight, p. 312.

‡ Medals of Creation, vol. ii. p. 742.

§ 38.

TEETH OF THE IGUANODON.

425

the base was *indented*, not broken off; proving that the shank had been removed by absorption from the pressure of a new tooth, which had grown up, and caused the old one to be thrown off.

LIGN. 103.—TOOTH OF THE IGUANODON: FROM TILGATE FOREST. (nat. size.)

Fig. 1. Front aspect, showing the longitudinal ridges, and denticulated margins of the crown: *a*, the denticulated margin; *b*, apex of the crown partly worn by use; *c*, transverse fracture of the fang, exposing a section of the medullary cavity occupied by the ossified remains of the pulp; *d*, the base of the denticulated border.

Fig. 2. The inner aspect of the same.

In the series of teeth before us (Ligns. 102, 103, 104), we may trace every gradation of this change; from the pointed, angular, perfect crown and fang (Lign. 102, fig. 2), and the partially worn specimen (figs. 4, 5), to the mere stump (figs. 1, 3); in which the summit is ground flat, and the shank entirely absorbed from the pressure of a successive tooth. The perfect teeth of the Iguanodon are distinguished by their prismatic form; the presence of two to four or five ridges, which extend down the front; and the denticulated lateral margins of the crown (Lign. 102, fig. 6). The latter appear as simple serrations in the figure, Lign. 103,*a*; but when viewed laterally (Lign. 102, fig. 6), are found to consist of denticulated plates.

§ 39.

THE MAIDSTONE IGUANODON.

427

39. THE MAIDSTONE IGUANODON. *Plate III.*—From the gigantic size of the fossil teeth, as compared with those of recent lizards, I was led to conclude that many of the colossal bones, collected from time to time in Tilgate Forest, belonged to the same kind of reptile; and by comparing the bones with those of an Iguana, (presented to me by Baron Cuvier,) I at length succeeded in determining many parts of the skeleton, and was enabled to restore, as it were, the form of the Iguanodon, and ascertain its proportions:* the correctness of my deductions was shortly to be put to the test, by a discovery in a neighbouring county.

In May, 1834, some workmen employed in a stone-quarry, in the occupation of Mr. W. H. Bensted, of Maidstone, observed in a mass of rock which they had blasted, several portions of what they supposed to be petrified wood; they preserved the largest piece for the inspection of the proprietor of the quarry, who, perceiving that it was a portion of bone belonging to some gigantic animal, gave directions that every fragment should be collected, and succeeded in obtaining those pieces, which, when united and completely developed, formed the highly interesting fossil here delineated, (Pl. III.)†.

* In stating that there was a general resemblance between the teeth and bones of the Iguanodon and those of the Iguana, it was never intended to affirm, that any close analogy existed; still less to assert, as some writers have supposed, that the living Iguana is a miniature representative of the colossal reptile of the wealden.

† The rock was shattered to fragments by the explosion, and the bones were broken into a thousand pieces: but after much labour I succeeded in uniting the several blocks of stone, and ultimately cleared and repaired the bones, and restored the specimen to its present state. It is placed under a large glass frame, in the palæontological gallery of the British Museum. The circular hole seen near the centre of the fossil, was made to introduce the charge of powder for blasting the rock.

428

THE WONDERS OF GEOLOGY.

LECT. IV.

This specimen consists of a considerable number of the bones of the inferior portion of the skeleton of an adult, but not aged, individual. The bones are imbedded in the stone in a very confused manner; few of them lying in their natural order of juxtaposition, and all being more or less flattened and distorted. The following are the most important, and the best preserved; but there are numerous fragments, too imperfect to admit of determination.

Two thigh-bones, each 33 inches long. *Plate* III. *figs.* 1, 2.

One leg-bone (tibia), 30 inches long. *Fig. 3.*

*Metatarsal* and *phalangeal* bones of the hind feet; these much resemble the corresponding bones of the hippopotamus. *Figs.* 4, 4, 4.

A claw-bone (ungual bone), which was originally covered by a horny investment; it resembles the corresponding bone of a land tortoise. *Fig. 5.*

Two *metacarpal* bones of the fore feet, each 14 inches in length. *Fig. 6.*

A radius, or bone of the fore-arm. *Fig. 7.*

Several *dorsal* and *caudal* vertebræ (bones of the spine and tail). *Figs.* 8, 8, 8.

Fragments of several ribs. *Figs.* 9, 9, 9.

Two *clavicles*, or collar bones, each 28 inches in length, resembling the bone figured *Plate IV. figs.* 1, 2, Geology of the South-East of England. These bones are of a very singular form, and differ essentially from any known clavicle. *Figs.* 10, 10.

Two large flat hatchet-shaped bones, which belong to the pelvis (*iliac bones*). *Figs.* 11, 11.

A *chevron-bone*, or inferior spinous process of a vertebra of the tail *Fig. 12*.

A portion of a tooth, and the impression of another.—The preservation of these relics was most fortunate, as the identity of the animal with the *Iguanodon* of Tilgate Forest is thereby completely established.

The geological position of this specimen forms an exception to what has been previously remarked of the remains of the *Iguanodon* from the Wealden; for while in the latter the bones are associated with terrestrial and fluviatile exuviae only, the Maidstone fossil was imbedded in a marine

§ 40.

VERTEBRÆ OF THE IGUANODON.

429

deposit.* This discrepancy, however, does not affect the arguments previously advanced, as to the fluviatile origin of the strata of the Wealden; it merely shows that part of the delta had subsided, and was covered by the chalk ocean, whilst the country of the Iguanodon was still in existence; and that the body of one of these reptiles was drifted far out to sea, and sunk down in the depths of the ocean: in like manner, as at the present day, bones of land quadrupeds may not only be engulfed in the deltas of rivers, but also in marine deposits far from land.

This specimen proves that the separate bones found in the strata of Tilgate Forest, and which I had assigned to the Iguanodon, solely from analogy, have been correctly appropriated.

40. VERTEBRÆ OF THE IGUANODON.—The peculiarities in the vertebral column of the Iguanodon are pointed out in the Medals of Creation,† and anatomical details would here be irrelevant; a few particulars must, however, be noticed. The transverse processes of the dorsal and lumbar vertebrae are very long and straight, indicating a considerable expanse of the abdominal cavity, suitable for the capacious viscera of a herbivorous quadruped. In the caudal vertebrae, both the spinous processes (Lign. 105, a, a,) and

* The stone in which the bones are imbedded is of that hard variety of the grey, arenaceous limestone, called *Kentish rag*, which is much employed in various parts of Kent, and in the west of Sussex, for building, and for repairing the roads. It abounds in the marine shells which are characteristic of that division of the chalk formation. In the quarry in which the remains of the Iguanodon were found, there have been discovered wood perforated by *lithodomis*, or boring shells; impressions of leaves and stems of trees, with *trigoniæ*, *ammonites*, *nautili*, &c.; conical striated teeth of the marine reptile called Polyptychodon (*ante*, p. 354), some of which are two inches in diameter at the base; scales and teeth of squaloid fishes, and maxillary bones of the Chimæa or Endaphodon of Sir P. M. Egerton. Molluskite abounds in these strata.

† Vol. ii. p. 745.

430

THE WONDERS OF GEOLOGY.

LECT. IV.

the *chevron bones*, (b, b,) are of great length ; the latter
have their bases so blended as to form but one face for
articulation with the truncated inferior angles of the body

LIGN. 105.—SIX CAUDAL VERTEBRÆ OF AN IGUANODON; FROM TILGATE FOREST.

(One-sixteenth natural size.)

a, a, Spinous processes, fifteen inches high. b, b, Chevron bones, imbedded in the stone near their original articulation between two of the vertebræ.

of the vertebræ, leaving a vertical and elongated channel,
for the passage of the large blood vessels of the tail. The
proportions of these elements of the caudal vertebræ indi-
cate a great vertical development of the tail. In the beau-
tiful specimen before us (*Lign.* 105) of six united caudal
vertebræ, imbedded in a block of Tilgate grit, with both
the upper and inferior spinous processes displayed, these
characters are strikingly obvious. The width, or rather
height, of that portion of the tail to which these bones
belonged, must have been at least twenty-seven inches.

432

THE WONDERS OF GEOLOGY.

LECT. IV.

been obtained from various localities of the Wealden. The
first fragment of a thigh-bone that came under my notice,
was a portion of the middle part of the shaft, which is of a
quadrangular form; and this was so large, shapeless, and
unintelligible, that many years elapsed before I obtained
any clue as to its real nature.* The toe-bones presented so
little correspondence with those of reptiles, and such a
similitude to the metatarsals of the large pachyderms, as for
example those of the Hippopotamus, that it was long ere
their true affinities could be determined.†

To convey an idea of the enormous size which some indi-
viduals must have attained, I may state that one perfect
thigh-bone is three feet eight inches long, and thirty-five
inches in circumference at the condyles, and that some
fragments indicate a greater magnitude. A leg-bone or tibia,
of which I have a large portion, must have been four feet
long; the corresponding thigh-bone would be a foot longer;
the entire length of the limb must therefore have exceeded
nine feet! These bones occur of very different sizes;
I have a femur only five inches long, and other bones, that
must have belonged to very young reptiles.

The femur of the Iguanodon is remarkable from the combination
of mammalian characters which it presents, in its well-marked head
and neck, trochanters, condyles, and medullary cavity. The head (Lign.
107, f,) is hemispherical, and projects inwards; and a laterally
flattened process or trochanter (a) forms an external buttress or
boundary of the neck of the bone, from which it is separated by a
deep, narrow, vertical fissure. The shaft of the bone is subquadran-
gular; a slightly elevated ridge, produced by the union of two broad,
flat, longitudinal surfaces, indicating the attachment of powerful

* This fragment is figured in Foss. Tilg. Forest, Pl. XVIII.

† Baron Cuvier, with that noble candour for which he was as
eminently distinguished as for his transcendent genius, wrote to me as
follows:—“Les fragmens d’os du métacarpe ou du métatarse, sont si
gros, qu’au premier coup d’œil je les avais pris pour ceux d’un grand
Hippopotame.”

§ 42.

FEMUR OF THE IGUANODON.

433

muscles, extends down the middle of the anterior face, and diverging
towards the inner condyle, gradually disappears. The shaft terminates
below in two large, rounded, and laterally-
compressed condyles (c, d), which are sepa-
rated in front and behind by a deep groove
(e). Near the middle of the shaft, the
mesial, or inner edge, forms a compressed
ridge, which expands into an angular pro-
jection, or trochanter (b). Thus the upper
part of the femur may be known by the
presence of the upper trochanter (a); and
if that process is broken away, the frac-
tured surface indicating its position will be
detected. If a fragment of the middle part
of the shaft only is found, the flattened
angular spaces, and the submedian tro-
chanter (b), or the mark of its attachment,
will identify it. The lower extremity of
the femur may be distinguished by the
deep groove (e) between the condyles, both
in front and behind. The medullary cavity
is very large.

42. PROBABLE FORM AND SIZE
OF THE IGUANODON.—From nume-
rous detached bones that have been
collected from various localities of
the Wealden, and with the aid of the
few specimens in which several are
collocated in the same block of stone,
the size and proportions of the body
and limbs of the Iguanodon have
been determined; yet but a vague
idea of the form and appearance of
the original animal can be derived
from the relics hitherto discovered.
For the great discrepancy between
the known parts of the skeleton,
and the corresponding bones in the

LIGN. 107.—LEFT FEMUR OF AN IGUANODON. From Brook Bay.

(The original, 40 inches in length.)

a, Upper trochanter.

b, Middle trochanter.

c, Inner, d, outer condyle.

e, Groove between the condyles.

FF

434

THE WONDERS OF GEOLOGY.

LECT. IV.

largest existing saurians, renders it vain to attempt the restoration of the form of this colossal reptile, till the skull, jaws, &c. are known. In all probability the entire or a considerable portion of the skeleton of a young Iguanodon, will sooner or later be brought to light, and yield the information necessary to enable the palæontologist to reconstruct the skeleton, and delineate the physiognomy of the living original.

In the present state of our knowledge we may, however, safely infer, that the body of the Iguanodon was equal in magnitude to that of the Elephant, and as massive in its proportions; for, being a vegetable feeder, a large development of the abdominal region may be inferred. Its limbs must have been of a proportionate size to sustain so enormous a bulk; one of the thigh-bones (in the British Museum), if covered with muscles and integuments of suitable proportions, would form a limb seven feet in circumference. The hinder extremities, in all probability, presented the unwieldy contour of those of the hippopotamus or rhinoceros, and were supported by very strong short feet, the toes of which were armed with claws like those of certain turtes. The fore-legs appear to have been less bulky, and were furnished with hooked claws resembling the ungueal phalanges of the Iguana. The teeth demonstrate the nature of the food required for the support of this herbivorous reptile, and the power of mastication it enjoyed; and the ferns, cycadeous plants, and coniferous trees, with which its remains are associated, indicate the flora adapted for its sustenance. But the physiognomy of this creature, from the peculiar modification of the skull and jaws, required for the attachment and support of the powerful muscles necessary for the trituration of tough vegetable substances, must have differed entirely from that of all known saurians.

The length of the Iguanodon has been variously estimated;

§ 43.

THE HYLÆOSAURUS.

435

the difference in the computation depending chiefly on the extent assigned to the tail, which in the Iguana and many other lizards is much longer than the body. If the tail of the fossil reptile was slender, and of the same relative proportions as in the Iguana, the largest individual would be fifty or sixty feet long; but it is more probable, and in fact almost certain, from the shortness of the bodies of the caudal vertebræ, that the tail was short, and flattened in a vertical direction, as in certain living reptiles—for example, the *Doryphorus*; in that case, the length of a full-grown Iguanodon would but little exceed thirty feet.*

From what has been advanced we may conclude, that the Iguanodon was a gigantic but inoffensive herbivorous reptile, which lived on the ferns, cycadæ, and coniferæ, that constituted the flora of the country of the Wealden, of which it appears to have been the principal inhabitant.

43. THE HYLÆOSAURUS, or *Wealden Lizard*; Plate IV.
—This is another reptile of the Wealden, possessing the same remarkable construction of the sacrum as the Iguanodon, and which I have distinguished by a name indicative of the geological formation in which its remains occur. The first and most important specimen of the Hylæosaurus was discovered in the summer of 1832, under the following circumstances.

Upon visiting a quarry in Tilgate Forest, which had yielded many organic remains, I perceived in some fragments of a large mass of calciferous grit, which had recently been broken up and thrown on the road-side, traces of numerous pieces of bones. I therefore collected all the recognizable portions of the block, and had them conveyed to my residence. Having cemented the fragments together, and chiselled off the stone in which the bones were imbedded, so far as their brittle state would admit, I succeeded, after much labour, in developing a considerable portion of

* Medals of Creation, p. 751.

FF 2

436

THE WONDERS OF GEOLOGY.

LECT. IV.

the skeleton of a reptile, in which are blended the osteologi-
cal characters of the crocodiles with those of the lizards.

The vertebrae of the neck (Pl. IV. 2), several of the
back (3, 3), many ribs (4, 4), the two coracoid bones
(7, 7), and scapulæ (8, 8), remain not far removed from
their natural order of juxtaposition. There are also several
dermal or skin bones, which supported the thick scales or
scutes; of these the most extraordinary are certain large
angular bones (5, 5, 6, 6), which lie in the direction of the
vertebral column, and appear to have extended along the
back, like the horny serrated fringe in the Iguana. Many
other existing lizards have appendages of this kind, which

LIGN. 108.—CYCLURA CARINATA.
(A recent Lizard, allied to the Iguana. Dr. Harlan.)*

in some genera are largely developed; as for example in the
*Cyclura* (Lign. 108).†

There are several detached bones dispersed in the block

* Medical and Physical Researches, by R. Harlan, M.D. F.G.S.
8vo. Philadelphia, 1835.

† Professor Owen doubts the correctness of this interpretation, and is disposed to regard these angular spines as abdominal ribs. He particularly dwells on the unsymmetrical form of some of these bodies, but which appears to me to have arisen from compression. The other objections are not more valid; and as it is now ascertained that the internal structure of these spines is identical with that peculiar modification known only in the true dermal bones, the evidence is in favour of this view of the subject.

§ 43.

THE HYLÆOSAURUS.

437

of stone; numerous vegetable remains, and carpolithes, or seed-vessels of the Clathraria (*ante*, p. 399), were detected in reducing the size of the mass.*

I subsequently obtained many bones of this reptile from a bed of clay near Crawley; and a most interesting specimen of part of the vertebral column, comprising nearly thirty dorsal and caudal vertebræ, with many dermal bones and spines, ribs, &c.

*Dermal bones and spines.†* The structure of the dermal bones is very peculiar, and closely resembles that of the ligamentous fibres of the *corium*, or skin, and seems to have resulted from an ossified condition of the dermal integument.‡ Upon inspecting the surface exposed by a transverse fracture of the oval scutes, minute osseous spiculæ, decussating each other at right angles, are visible to the naked eye; and under the microscope, the same arrangement is found to prevail in the minutest bony fibres; the medullary canals have fine lines radiating from them.

I have very lately been able to ascertain that the same internal structure characterizes the spinous bones (*Plate* IV. 5, 6); and this fact tends to confirm my opinion, that they are also ossified dermal processes, which formed a longitudinal crest along the back of the animal.§

* For further particulars see my Geology of the South-East of England, p. 316. Pl. V. of that work is an excellent lithograph of this specimen, by Mr. Pollard, of Brighton.

† Medals of Creation, vol. ii. p. 704.

‡ See my Memoir on the Fossil Reptiles discovered in Tilgate Forest, Philos. Trans. for 1841.

§ The following are Professor Owen's remarks on the dermal scutes:—

"By the kindness of Dr. Mantell I have been favoured with the means of submitting the structure of a dermal scute to microscopical examination. The medullary canals, which are stained brown, as if with the hematosine of the old reptile, differ from those of ordinary bone, in the paucity or absence of concentric layers. They are situated in the interspaces of straight, opaque, decussated filaments, which frequently seem to be cut short off, close to the medullary canals.

438

THE WONDERS OF GEOLOGY.

LECT. IV.

The Hylæosaurus was probably a terrestrial herbivorous
reptile, between twenty and thirty feet in length. The
modification of form in the bones composing
the sternal arch—in which a coracoid of the
lacertian type is united with a scapula like
that of the crocodiles—together with other os-
teological peculiarities, and the largely deve-
loped dermal processes, all combine to point
out the original as a most extraordinary type of
reptilian organization.

LIGN. 109.
TOOTH OF THE
HYLÆOSAURUS?

From Tilgate
Forest; natural
size.

As no portion of the jaw has been found, the
characters of the dental organs are unknown;
but I have long considered the teeth before us
(Lign. 109) as probably referable to the Hylæo-
saurus. They are generally from one inch to one
and a half inch long, with a cylindrical shank,
which enlarges into an obtuse, lanceolate crown,
convex in front, and depressed behind; the
margins of the crown are invariably worn, as if by use :
the internal structure consists of firm dentine, with ex-
tremely minute tubes radiating from the centre to the
periphery of the tooth, which has a thick coat of enamel.*

44. PTERODACTYLES OF THE WEALDEN.—In the Wealden, numerous fragments of bones, which from their tenuity

Very fine lines may be observed to radiate from some of the medullary canals; irregularly shaped, oblong, and angular radiated cells, are scattered through most parts of the osseous tissue, but they present less uniformity of size than do the Purkinjian cells in ordinary bone. The most striking characteristics of the dermal bone, are the long, straight, spicular fibres which traverse it, and decussate each other in all directions, representing, as it seems, the ossified ligamentous fibres of the original corium.”—*British Association Reports*, for 1841, p. 115. This description will equally apply to the internal structure of the dorsal spines; but the latter has not yet been seen by Professor Owen, as I have but very recently obtained a specimen for microscopical examination.

* Medals of Creation, vol. ii. p. 737.

§ 44.

PTERODACTYLES OF THE WEALDEN.

439

must have belonged to animals capable of flight, have been
obtained from various localities. Several are figured in
my Fossils of Tilgate Forest. The imperfect state of
the specimens renders it extremely difficult to determine
whether any of these bones belong to a higher order of
animals than reptiles—whether, in fact, some of them are
not referable to birds. The solution of this problem has
long been attempted by a rigorous examination of every
specimen; and but a short time since
it was supposed that unquestionable
relics of birds were among the fossils
which I had obtained from the strata
of Tilgate Forest; and a supposed
tarso-metatarsal bone of a Wader was
regarded as affording unequivocal evi-
dence on this point.* Recently, how-
ever, the question has been reduced
to its former state; for the presumed
tarso-metatarsal bone, proves to be a
humerus or arm-bone; and, as Pro-
fessor Owen now believes, of an un-
doubted Pterodactyle; an opinion
which Mr. Bowerbank states is con-
firmed by the microscopical examina-
tion of its internal structure. Be this
as it may, we may safely infer that
Pterodactyles were comprised in the
fauna of the Wealden.

I subjoin a correct representation
of the inferior portion of this bone
(Lign. 110). In my opinion, the upper
extremity indicates a more expanded

LIGN. 110.—THE DISTAL OR LOWER PORTION OF THE HUMERUS OF AN ANIMAL CAPABLE OF FLIGHT.

From the strata of Tilgate Forest.
(Anterior aspect; nat. size.)

a, Oval cicatrix indicating the insertion of a powerful muscle.

b, Ridge for the attachment of fasciæ or muscles.

* See my Memoir on the Bones of Birds discovered in the strata of Tilgate Forest; Geol. Trans. vol. v. New Series, p. 175.

440

THE WONDERS OF GEOLOGY.

LECT. IV.

head than is observable in the known humeri of Pterodactyles;* and it appears to me impossible to pronounce, with any certainty, as to the true character of the animal to which it belonged, till other specimens are obtained.†

45. BIRDS OF THE WEALDEN.—In describing the fossil remains of the mammalia of the eocene or ancient tertiary epoch, it was stated that species of several existing genera of birds were contemporaneous with the palæotheria and other extinct pachyderms, but that no vestiges of this class had been found in the chalk, or in strata of an earlier date. In my Fossils of Tilgate Forest, I mentioned, that after selecting from the bones which seemed to belong to animals capable of progression through the air, those which appeared to be referable to the Pterodactyles, several remained which bore so striking a resemblance to those of waders that I ventured to refer them to that order of birds; an opinion which was corroborated by Baron Cuvier, to whom I submitted them on his last visit to England, in 1830. Subsequently, Professor Owen instituted a rigid examination of these bones, and satisfied himself that some of them unquestionably belonged to a species of wading bird.‡ More recently, this distinguished physiologist has seen reason to alter his opinion; and upon finding that the supposed tarso-metatarsal bone is a humerus (ante, p. 439), now affirms that all the bones of the wealden referable to flying animals, are reptilian. With the view of determining if possible this difficult problem, Mr. Bowerbank instituted a microscopical investigation of the intimate structure of bone in birds and reptiles; and has commu-

* See Geol. Trans. vol. v. Pl. XIII. fig. 3.

† See Prof. Owen on supposed fossil bones of Birds; Geol. Journal, 1846, p. 96; and my remarks in the same work, p. 104, on the Fossil remains of Birds in the Wealden; the figure accompanying my paper is most inaccurately represented by the lignograph.

‡ See Medals of Creation, vol. ii. p. 805.

§ 45.

BIRDS OF THE WEALDEN.

441

nicated the result to the Geological Society. This eminent microscopical observer has found a recognizable difference in the form and proportion of the minute cells of the bones, which he believes is constant, and by which the smallest fragment may be referred to its proper class. In *Birds*, under a power of 500 linear, by transmitted light, the cells are found to have a breadth in proportion to their length of from one to four or five; while in *Reptiles* the length exceeds the breadth ten or twelve times. For example :—

> In the Albatross, the width of the cell is ¼ the length.

> — Crocodile — — — ½ —

Applying this test to the supposed bones of birds from the chalk, Mr. Bowerbank finds that the specimens regarded by Professor Owen as belonging to an extinct species of Albatross,* are reptilian; the length of the cells being twelve times that of their width, as in the bones of the cranium, jaws, &c. of an undoubted Pterodactyle (*P. giganteus*) found in the same quarry, and to which he therefore refers them.†

The wealden bones, subjected to the same interrogatory, gave different results. The bone figured *Lign.* 110 has cells of the reptilian type, and is therefore declared by Mr. Bowerbank to be that of a Pterodactyle: while some of the other specimens (especially that examined by Baron Cuvier, and figured in Geol. Trans. vol. v. Pl. XIII. fig. 6.) have short elliptical cells as in true birds, and are presumed to belong to that class. At the present time, the question

* Medals of Creation, vol. ii. p. 803.

† I would here remark, that these bones are so extremely *thin*, as to render it most improbable that they could ever have sustained such an instrument of flight, as the powerful wing of the Albatross or of any other bird; their tenuity is in fact such as to point out their adaptation to support an expanded membrane, but not pinions.

442

THE WONDERS OF GEOLOGY.

LECT. IV.

as to the existence of warm-blooded animals capable of
flight, during the wealden and cretaceous epochs, must,
therefore, be regarded as in the same state of uncertainty,
as when I first announced the occurrence of the supposed
bird's bones in the strata of Tilgate Forest, in 1827. I am,
however, inclined to believe, that the presence of birds in
the secondary formations, will sooner or later be satisfac-
torily established; and I would, therefore, retain the name
of *Palæornis Cliftii*, (*Medals of Creation*, p. 806,) for the
wealden ornitholites.

46. THE COUNTRY OF THE IGUANODON.—By this survey of the strata and organic remains of the Wealden, we have acquired data from which, by the principles of induction already explained (p. 367), we may obtain secure conclusions as to the nature of the country whence those spoils were derived, of the animals by which it was inhabited, and of the vegetables that grew upon its surface. Whether that country was an island or a continent cannot be determined; but that it was diversified by hills and valleys, and irrigated by streams and rivers, and enjoyed a climate of a higher temperature than any part of modern Europe, is most evident. Arborescent ferns, palms, coniferous trees, and cycadous plants, constituted its groves and forests, and delicate ferns the vegetable clothing of its soil; and in its fens and marshes the equiseta, and plants of a like nature, prevailed. Its principal herbivorous quadruped was the enormous lizard, the Iguanodon; its carnivora, the Megalosaurus and other predaceous reptiles; crocodiles and turtles frequented its rivers, and deposited their eggs on the banks and shoals; and its waters teemed with fishes, mollusca and crustaceans. That the soil was of a sandy nature on the hills and plains, and argillaceous in the lowlands and marshes, may be inferred from the vegetable remains, and the lithological character of the strata in which they are imbedded. Some inferences relating to