"Now nearly the whole of the shells in the beds of Kentish Rag," Mr. Bensted remarks, "have their shells open, as if they were dead before their envelopment in the deposit. And, from the large quantity of water-worn fragments of wood perforated by Pholades imbedded with them, it seems probable that this stratum had originally been a sand-bank covered with drifted wood and shells, thus presenting a very analogous condition to the phenomenon above described." The gelatinous bodies of the Trigoniæ, Ostreæ, Rostellariæ, Terebratulæ, &c., detached from their shells, may have been intermingled with the drifted wood in a sand-bank; while, in some instances, the animal matter would remain in the shells, be converted into molluskite, and retain the form of the original, as in the spiral univalve, represented in section, Lign. 139, fig. 3.

A microscopical examination of the Maidstone molluskite detects, with a low power, innumerable portions of the nacreous laminæ of shells, intermingled with the carbonaceous matter, many siliceous spicula of Sponges, minute spines of Echinoderms, and fragments of Corals; these extraneous bodies probably became entangled among the floating animal matter. A large proportion of the shelly laminæ, examined with a high power, displays the peculiar structure of the Terebratulæ (see Lign. 126, fig. 2^a), of which several species are abundant in the Kentish Rag.

The dark masses and veins so common in the Sussex and Purbeck marbles are produced by molluskite. If at the period of their envelopment the shells were empty, they became filled either with grey marl and limestone, or with white calcareous spar; but if they enclosed the bodies of the Mollusks, the soft mass was changed into carbonaceous matter; and in polished sections of the marble, the molluskite appears either in black or dark brown spots, or fills up the cavities of the shells. The dark blotches and veins observable in the fine pillars of Purbeck marble in the Temple Church, London, are produced by molluskite; and the most beautiful slabs of Sussex marble owe their appearance to the contrast produced by this black substance in contact with white calcareous spar.[392]

Carbon, resulting from animal remains, is of frequent occurrence in many strata; and the fetid emanations from certain limestones, upon being broken or rubbed, are attributable to the evolution of sulphuretted hydrogen, from the animal matter which they contain.

Geological Distribution of the Bivalve and Univalve Mollusca.—If the more rare and splendid organic remains may be regarded as the "Medals of Creation," the fossil testaceous mollusca, from their durability, numbers and variety, may be considered as the current coin of Geology. Occurring in the most ancient fossiliferous strata in small numbers, and of peculiar types,—becoming more abundant and varied in the secondary formations,—and increasing prodigiously, both numerically and specifically, in the tertiary, these relics are of inestimable value in the identification of a stratum in distant regions, and in the determination of the relative age of a series of deposits. To the solution of the former problem the sagacity of the late Dr. William Smith first suggested their applicability;[393] while the idea, so happily conceived, and so philosophically candied out, by Sir C. Lyell, of arranging that heretofore chaotic mass of deposits, termed the Tertiary, into groups, by the relative number of recent and extinct species of shells, demonstrated the important aid to be derived from this class of organic remains, in the determination of some of the most difficult questions in geological science.

Many useful tables have been constructed by Professor Phillips,[394] Sir C. Lyell, M. Deshayes, M. D'Orbigny, Prof. E. Forbes, and other eminent observers, to illustrate the geological distribution, in the several formations, of the genera and species of fossil shells hitherto described. To the English student, Mr. Morris's "Catalogue of British Fossils," of which an enlarged edition is in the press, will be the most valuable for reference. In the works which we have especially recommended for reference (ante, p. 10.), figures are given of some of the characteristic shells from each formation, as follow; commencing with the most ancient deposits.

Silurian System. Ly. p. 350.

Orthis orbicularis; Ly. fig. 409.
——— grandis;—fig. 427.
Terebratula navicula;—fig. 410.
————– Wilsoni;—fig. 413.
Pentamerus Knightii;—fig, 411.
————— lævis;—fig. 426.
Atrypa reticularis; fig. 414. Wond. p. 786.
Lingula Lewisii; Ly. fig. 412.
Strophomena depressa;—fig. 421.

Devonian System. Ly. p. 342.

Calceola sandalina; Ly. fig. 403.
Stringocephalus Burtini;—fig. 404.
Megalodon cucullatus;—fig. 405.

"The Silurian System," by Sir R. I. Murchison, a splendid work on the rocks and fossils of the above formations, contains numerous figures of the shells peculiar to each group of strata; and many other species are delineated in the Memoir on the Devonian deposits of Devonshire and Cornwall, by Sedgwick and Murchison, Geol. Trans. New Series, vol. v. plates lii-lvii. A Memoir on the Palæozoic Rocks of Germany and Belgium, by the same distinguished geologists, is also accompanied by many figures of fossil shells belonging to the same geological epochs. Geol. Trans. New Series, vol. vi.

See also Prof. M'Coy's "Silurian Fossils of Ireland," and his Description of the British Palæozoic Fossils in the Woodwardian Museum at Cambridge, in Prof. Sedgwick's "Synopsis of the Classification of the British Palæozoic Rocks," of which two Parts are already published.

Carboniferous System. Ly. 308. Wond. p. 736.

Producta punctata; Wond. p. 736.
———– Martini; Ly. fig. 390.
Pleurotomaria flammigera; Lign. 136, fig. 4.
Euomphalus pentangulatus; Lign. 136, fig. 1.
Natica plicistria; Lign. 136, fig. 3.
Spirifera trigonalis; Wond. p. 736.
———– triangularis; Wond. p. 736.
———– glabra; Ly. p. 389.
Serpula carbonaria; Ly. fig. 375.
Avicula papyracea;—fig. 378.

For the shells of the Mountain Limestone, reference should be made to the second vol. of Prof. Phillips's "Geology of Yorkshire;" to Prof. M'Coy's "Carboniferous Limestone Fossils of Ireland;" and to Prof, de Konick's "Anim. Foss. Belg." The fossils of other portions of the Carboniferous System are illustrated in Phillips's "Palæozoic Fossils of Devon;"[395] and in Prestwich's Memoir on Coalbrook Dale (Geol. Trans.).

Magnesian Limestone and Trias. Ly. p. 301.

Prof. King's elaborate Monograph on the Permian Fossils (published by the Palæontographical Society) should be consulted by the student.

Lias. Ly. p. 273.

Pleurotomaria Anglica; Ly. p. 39.
Avicula inæquivalvis; Ly. fig. 302.
Plagiostoma giganteum; Ly. fig. 303.
Gryphæa incurva; Lign. 127.

Oolite. Ly. p. 257.

Gryphæa virgula; Ly. fig. 268.
Ostrea deltoidea (Kimmeridge Clay);—fig. 269.
Trigonia gibbosa;—fig. 270.
———– clavellata; Lign. 127.
———– costata; Lign. 127.
Nerinæa Goodhallii; Ly. fig. 274.
Diceras arietinum;—fig. 275.
Pleurotomaria;—fig. 299.
Terebratula spinosa;—fig. 297.
————– digona;—fig. 283.
Ostrea Marshii;—fig. 300.
Phasianella Heddingtonensis;—fig. 58.

Many of the characteristic shells of the Oolite and Kimmeridge Clay, are figured in Plates XXII. and XXIII. of Dr. Fitton's Memoir on the Strata below the Chalk; Geol. Trans. New Series, vol. iv.

The fossil shells of the Great Oolite are figured and described by Messrs. Morris and Lycett, in the Memoirs of the Palæontographical Society; and valuable Papers on the Brachiopods of the Oolite and Lias, by Mr. Davidson, have been published by the same Society.

Wealden and Purbeck. Wond. vol. i. Geol. S. E., Foss. Tilg. For., and Ly. p. 225.

Melanopsis; Wond. pp. 401 and 404.
Cyclas;—p. 404.
Paludina Sussexiensis;—p. 401.
Neritina Fittoni;—p. 401.
Mytilus Lyellii;—p. 405.
Unio antiquus; Geol. S. E. p. 250, fig. 1.
—— compressus;—fig. 2.
—— aduncus;—fig. 3.
—— porrectus;—fig. 4.
Valdensis;—Min. Conch. pl. 646, and Lign. 131.
Corbula alata; Ly. p. 229.
Ostrea distorta;—p. 232.

The shells of the Wealden are also figured by Dr. Fitton, Geol. Trans. New Series, vol. iv. Pl. XXI.

Chalk Formation.

I.—Shanklin, or Lower Greensand. Ly. p. 219.

Dr. Fitton's Memoir, previously quoted, contains numerous figures of the characteristic shells of this division of the Chalk, particularly of the species which abound in the celebrated Whetstone of Devonshire. Geol. Trans. New Series, vol. iv. Pl. XIII-XVIII. See also Prof. E. Forbes's Catalogue of Lower Greensand Fossils, in the Quart. Geol. Journal, vol. i.

II.—Galt and Upper Greensand. Wond. p. 307; Ly. p. 218.

Inoceramus concentricus; Wond. p. 330, fig. 1.
————— sulcatus;—fig. 3.
Terebratula lyra; Ly. fig. 219.
Pecten quinquecostatus;—fig. 203.
Ostrea carinata;—fig. 204.

In Plates XI. and XII. of Dr. Fitton's Memoir, there are figures of more than twenty characteristic shells of this division of the Chalk.

III.—White Chalk. Ly. p. 211, Foss. South D., Geol. S. E.

Some cretaceous species are delineated in Lign. 125, 126, 128, 129, 130, 138; and Sir C. Lyell figures other species; but I must refer the student to the Foss. South D., Geol. S. E., and Dixon's Fossils of Sussex, as accessible works containing numerous figures of the fossil shells of the Chalk. Accurate descriptions and representations of all the British chalk shells, however, are still much required. Mr. Davidson has done much towards the illustration of our Cretaceous Brachiopods; and the shells of the Cretaceous strata of the United States are figured and described in an elegant work by Dr. Morton, of Philadelphia.

Tertiary Formations.

  I.—Eocene. Ly. p. 174; Wond. p. 226.
 II.—Miocene. Ly. p. 168.
III.—Pliocene. Ly. p. 161.

The specimens figured by Sir C. Lyell have been so carefully selected, and are so well engraven, as to present a coup-d'œil of the most characteristic shells of the three grand divisions of the Tertiary Deposits.

I have reserved for especial mention in this place, the work, which will afford the student of British fossil Conchology the most important aid in the identification of specimens, namely, the "Mineral Conchology of Great Britain," by the late eminent naturalist, Mr. James Sowerby, and continued by his son, Mr. James De Carle Sowerby; in six volumes 8vo., with several hundred coloured plates. Unfortunately, this work has long been discontinued; and the rapid progress of discovery, and the numerous foreign publications on every department of fossil conchology, almost forbid the hope that it will be resumed by the present proprietor. Although the high price of this work places it beyond the reach of many individuals, it will be found in most libraries of Natural History.

On the Collection and Arrangement of Fossil Shells.—The instructions already given for the collection of corals, echinoderms, &c., will have familiarized the student with the methods generally adopted, and render it unnecessary to enter into much detail. The shells in arenaceous deposits, particularly in those of the Tertiary formations, are commonly so perfect, as merely to require careful removal: those in the clays are more fragile, and must be extracted with great caution; and, when very delicate, should be left attached to the clay or shale. The specimens extracted entire may be kept either in paper trays, lined with wadding, or fixed to pieces of card or thin board covered with paper, by thick gum-water; three or four specimens being attached in different positions, so as to expose the essential characters, as the aperture, spire, and back of the univalves, and the hinge, muscular imprints, &c. of the bivalves. Where only casts remain, search should be made for an impression of the outer surface of the shell, and a cast taken of it in wax, kneaded bread, or plaster of Paris. In indurated clays, sometimes both shells and casts may be obtained; and a specimen of each should be preserved. Mastic varnish, or solution of gum tragacanth, delicately applied to fragile shells, tends to preserve them, and improves their appearance. It is desirable to collect the same species in various states of growth; the form of the young shell (as in Rostellaria ampla, of Solander) often differing essentially from that of the adult. It will be found convenient to have trays or boards of different colours; and to select one tint for the shells collected from a particular formation, or deposit; for example, the newer Tertiary may be placed on yellow paper; the older, or Eocene fossils, on light-blue. It is also desirable to separate the marine from the fresh-water species.

Shells imbedded in chalk, limestone, &c., often require much labour to display their more delicate and important characters. For clearing chalk specimens, a stout penknife, and a few gravers or gouges of various sizes, will be necessary; and by a little practice, the spines of the Spondylus (Lign. 128), and the beaks and hinge of Inocerami (Lign. 129), &c., may be readily exposed. A small stiffish brush, used with water, is also serviceable. The shells in compact stone, as those of the mountain limestone, must generally be cleared with the hammer and chisel. Common species may be broken out, and, from several examples, probably one or two will be found perfect; but choice and rare specimens should not be thus risked; they will amply repay the trouble of the less expeditious method of chiselling away the surrounding stone. Casts may be taken in gutta percha, &c.

To determine the names of the specimens that he has collected should be the next care of the student. No method will so readily initiate the young collector in fossil conchology, as the careful examination of a small series of the common species, with their names attached.[396] By the geological map,[397] the nature of the deposit in which the locality of the specimens is situated, may be ascertained; and the remarks previously advanced on the prevailing shells of each formation, will afford a general idea of the genera to which they belong; and, by referring to the figures quoted, the specific names may be determined.

I subjoin a list of some localities of fossil shells, to direct research in places which are likely to be productive.

BRITISH LOCALITIES OF FOSSIL SHELLS.

Aldborough, Suffolk. The usual shells of the Crag.

Alum Bay, Isle of Wight. Eocene tertiary; marine and fresh-water shells.

Ancliff. Great variety of minute shells of the Oolite.

Arundel, Sussex. Chalk-pits in the neighbourhood.

Atherfield, Isle of Wight, Shells of the lower beds of the Lower Greensand, in great variety and abundance.

Aylesbury, Bucks. Kimmeridge Clay: near Hartwell.

Aymestry. Pentamerus, and other Silurian shells.

Barnstaple, North Devon. Numerous Devonian shells.

Barton Cliff, Hants. Eocene shells in profusion.

Bedford. Lower Oolite, Terebratulæ, Ostreæ, Myadæ, &c.

Binstead, near Ryde, Isle of Wight. Tertiary: in the stone-quarries, terrestrial and fresh-water shells, as Bulimus, Helix, Limncæ, and Planorbis.

Blackdown, near Collumpton, Devon. Greensand. Numerous silicified shells, of great beauty. Trigonia, Venus, Corbula, Rostellaria, &c. &c.

Bognor Rocks, Sussex. Eocene Tertiary. Vermetus, Pectunculus, Pinna, Voluta, &c.

Bolland. Numerous shells of the Mountain Limestone.

Bradford, Wilts. Numerous Oolitic shells. Avicula.

Bramerton Hill, near Norwich. Shells of the Norfolk Crag.

Brighton. Strondylus, Terebratula, Ostrea, Pecten, Inoceramus, &c. Many species in the chalk.

Bromley, Kent. Eocene Tertiary. Oyster conglomerate.

Brook-point, Isle of Wight: about one mile east of the Chine. Wealden: Unio valdensis, Cyclades, Paludinæ, &c.

Brora, Scotland. Oolite. Pholadomya, Sanguinolaria, &c.

Calbourn, Isle of Wight. Tertiary. Fresh-water Univalves.

Cambridge. In the Galt and Chalk-marl, the usual shells.

Castle Hill, near Newhaven, Sussex. In the Tertiary strata, on the summit of the hill. Numerous Potamides, Cyclades, and other fresh-water shells, Ostreæ, with pebbles.

Chardstock, Devon. The fossils of the Lower Chalk.

Cheltenham. Fine shells of the Oolite and Lias.

Chute, near Longleat, Wilts. Greensand shells, in abundance.

Clayton, near Hurst, Sussex. In Chalk-marl, many rare shells; as, Dolium nodosum (Min. Conch. tab. 326.)

Clifton. Carboniferous Limestone. Spirifera, Producta, &c.

Coalbrook Dale. Silurian and Carboniferous fossils.

Cork. In the vicinity. Carboniferous limestone shells.

Crich Hill, Derbyshire. The usual shells of the Mountain Limestone.

Cuckfield, Sussex. In the Sandstone and Grit, fresh-water shells of the Wealden.

Dudley. Profusion of shells of the Silurian strata.

Dundry, near Bristol. Beautiful shells in the Inferior Oolite.

Earlstoke, Wilts. Many shells of the Greensand.

Faringdon, Berks. The usual shells of the Oolite in the Coral Rag, &c.; and of the Greensand, in the Gravel-pits.

Folkstone, Kent. Galt. Inoceramus, Arca, Rostellaria, Dentalium, &c. Lower Greensand, Gryphæa, Ostrea, &c.

Gravesend. Beautiful shells of the White Chalk.

Hampstead Cliff, Isle of Wight. Fresh-water Tertiary shells.

Hampton Quarry, near Bath. Abounds in Oolitic shells.

Hartwell, Bucks. On the estate of Dr. Lee, beautiful shells of the Kimmeridge Clay.

Harwich Cliff, Essex. The Crag shells. Voluta Lamberti.

Hastings, Sussex. Fresh-water shells of the Wealden.

Headon Hill, Isle of Wight. Fresh-water Tertiary shells in profusion.

Heddington. Oysters in Kimmeridge Clay (Ostrea deltoidea). Perna, Gervillia, Trigonia, &c.

Highworth, Wilts. Very fine Trigoniæ, and other Oolitic, shells, in the stone-quarries.

Hollington, near Hastings. Wealden. Fresh-water bivalves, &c.

Holywell, near Ipswich. Shells of the Crag, abundantly.

Hordwell Cliff, Hants. The usual shells of the Eocene deposits, in immense quantity, variety, and perfection.

Horningsham, near Frome, Wilts. Oxford Clay. Terebratula, Pecten, &c. in great numbers.

Horsham, Sussex. Fresh-water shells of the Wealden, in the stone-quarries.

Humbleton Hill, Sunderland. Permian fossils.

Hythe, Kent. Greensand. Trigonia, Gryphæa, Pecten, &c.

Ilminster, Somerset. Brachiopoda, &c. Inf. Oolite and Marlstone.

Ipswich. The usual Crag shells.

Langton Green, near Tunbridge Wells. Wealden. In the sandstone quarries, Uniones, Cyclades, &c.

Leckhampton Hill, near Cheltenham. Numerous shells of the Inferior Oolite and Lias.

Lewes. Inoceramus, Pecten, and usual shells of the White Chalk and Chalk Marl.

Ludlow. Pentamerus, Spirifera, &c. and other Silurian shells.

Lyme Regis. Lias. Plagiostoma, Gryphæa, Trochus.

Malton. Beautiful shells of the Oolite.

Matlock, Derbyshire. The mountain limestone in the vicinity abounds in the characteristic shells Leptæna, Spirifer, &c.

Minchinhampton. Numerous shells of the Great Oolite.

Osmington, near Weymouth. Purbeck; fresh-water and marine shells: Oolite; Trigonia, Gervillia, Perna, Pholadomya, and many other genera.

Portland, Isle of. Oolite. In the stone-quarries immense numbers of the genera Trigonia, Venus, Ostrea, Pecten, &c.

Pluckley, Kent. Lower Greensand. Trigoniæ, Terebratulæ, &c.

Radipole, near Weymouth. Trigonia, Pholadomya, &c. in Oxford Clay.

Sandgate, near Margate. In the Greensand, the usual shells.

Scarborough. In the cliffs along the shore, a profusion of Oolitic and Liassic shells.

Selbourne, Hants. In the firestone, Ostrea carinata and other characteristic shells.

Shalfleet, Isle of Wight. In tertiary fresh-water limestone, shells of various genera, as Bulimus, Helix, Planorbis, &c.

Shanklin Chine. Greensand. In the cliffs along the shore, Terebratidæ, Gryphites, Gervilliæ, and many other shells.

Sharnbrook, Bedfordshire. The usual shells of the Cornbrash and Lower Oolite.

Sheppey, Isle of. Eocene. London Clay shells, in abundance.

South Petherton, Somerset. Terebratulæ, Pholadomya, Ostreæ, Pleurotomariæ, &c. of the Marlstone.

Stamford, Lincolnshire. Lower Oolite. Univalves and bivalves in profusion.

Stonesfield, Oxfordshire. Trigoniæ and other shells of the Lower Oolite.

Stubbington Cliff, near Portsmouth. Eocene shells.

Swanage. In the quarries in the vicinity, the prevailing fresh-water shells of the Purbeck limestone.

Swindon, Wilts. Oolite. The Portland limestone abounds in the usual shells of that deposit. Trigoniæ, Gervilliæ, &c.

Taunton, Somersetshire, (Pickeridge Hill, &c.) Lima, Pecten, and other Liassic shells.

Tisbury, Wilts. Beautiful Trigoniæ, and other shells of the Portland Oolite.

Vincent's, St., near Clifton. The rocks abound in the usual shells of the mountain limestone.

Walton, Essex. Shells of the Crag, in great variety.

Weymouth. The Oxford Clay and other strata in the vicinity contain great variety of fossil shells.

Whitecliff Bay, Isle of Wight. Eocene. Marine and fresh-water shells.

Worthing. The chalk quarries in the neighbourhood are remarkably prolific in the usual species; and yield Sphærulites.

Note.—A comprehensive list of the localities for Lower Palæozoic shells, &c. is given by Prof. M'Coy in the second Fasciculus of the "British Palæozoic Fossils;" and in the little "Stratigraphical List," published by Mr. Tennant, reference is carefully made to the localities for the fossils of every formation.

END OF VOL. I.

R. CLAY, PRINTER, BREAD STREET HILL.

BOHN’S SCIENTIFIC LIBRARY.

MANTELL’S

MEDALS OF CREATION.

VOL. II.

THE

OR,

FIRST LESSONS IN GEOLOGY,

AND

THE STUDY OF ORGANIC REMAINS.

BY

GIDEON ALGERNON MANTELL, LL.D. F.R.S. V.P.G.S.

PRESIDENT OF THE WEST LONDON MEDICAL SOCIETY, ETC. AUTHOR OF THE WONDERS OF GEOLOGY, ETC.

IN TWO VOLS.—VOL. II.

CONTAINING

WITH NOTES OF GEOLOGICAL EXCURSIONS.

SECOND EDITION, ENTIRELY REWRITTEN.

LONDON:
HENRY G. BOHN, YORK STREET, COVENT GARDEN.

LONDON:
R. CLAY, PRINTER, BREAD STREET HILL.

DESCRIPTION

OF THE

FRONTISPIECE OF VOL. II.

PLATE II.

Illustrative of the mode of developing Fossil Fishes in Chalk.

Osmeroides Mantelli: a Fossil Smelt; from the Chalk, Lewes.

See page 626.

(One-third natural size.)

LIST OF LIGNOGRAPHS IN VOL. II.

(Illustrative of Fossil Zoology.)