SECONDARY EPOCH. (continued 2)

Lower Oolite Fauna.

The most salient and characteristic feature of this age is, undoubtedly, the appearance of animals belonging to the class of Mammals. But the organisation, quite special, of the first of the Mammalia will certainly be a matter of astonishment to the reader, and must satisfy him that Nature proceeded in the creation of animals by successive steps, by transitions which, in an almost imperceptible manner, connect the beings of one age with others more complicated in their organisation. The first Mammals which appeared upon the earth, for example, did not enjoy all the organic attributes belonging to the more recent creations of the class. In the latter the young are brought forth living, and not from eggs, like Birds, Reptiles, and Fishes. But the former belonged to that order of animals quite special, and never numerous, the young of which are transferred in a half-developed state, from the body of the mother to an external pouch in which they remain until they become perfected; in short, to marsupial animals. The mother nurses her young during a certain time in a sort of pouch external to the body, in the neighbourhood of the abdomen, and provided with teats to which the young adhere. After a more or less prolonged sojourn in this pouch, the young animal, when sufficiently matured and strong enough to battle with the world, emerges from its warm retreat, and enters fully into life and light; the process being a sort of middle course between oviparous generation, in which the animals are hatched from eggs after exclusion from the mother’s body, like Birds; and viviparous, in which the animals are brought forth alive, as in the ordinary Mammals.

In standard works on natural history the animals under consideration are classed as mammiferous Didelphæ. They are brought forth in an imperfect state, and during their transitional condition are suckled in a pouch supported by bones called marsupial, which are attached by their extremities to the pelvis, and serve to support the marsupium, whence the animals provided with these provisions for bringing up their progeny are called Marsupial Mammals. The Opossum, Kangaroo, and Ornithorhynchus are existing representatives of this group.

Fig. 110.—Jaw of Thylacotherium Prevostii.

Fig. 111.—Jaw of Phascolotherium.

The name of Thylacotherium, or Amphitherium, or Phascolotherium, is given to the first of these marsupial Mammals which made their appearance, whose remains have been discovered in the Lower Oolite, and in one of its higher stages, namely, that called the Great Oolite. Fig. 110 represents the jaw of the first of these animals, and Fig. 111 the other—both of the natural size. These jaw-bones represent all that has been found belonging to these early marsupial animals; and Baron Cuvier and Professor Owen have both decided as to their origin. The first was found in the Stonesfield quarries. The Phascolotherium, also a Stonesfield fossil, was the ornament of Mr. Broderip’s collection. The animals which lived on the land during the Lower Oolitic period would be nearly the same with those of the Liassic. The insects were, perhaps, more numerous.

Fig. 112.—Ammonites Herveyii.

Fig. 113.—Terebratula digona.

The marine fauna included Reptiles, Fishes, Molluscs, and Zoophytes. Among the first were the Pterodactyle, and a great Saurian, the Teleosaurus, belonging to a family which made its appearance in this age, and which reappears in the following epoch. Among the Fishes, the Ganoids and Ophiopsis predominate. Among the Ammonites, Ammonites Humphriesianus, A. Herveyii (Fig. 112), A. Brongniarti, Nautilus lineatus, and many other representatives of the cephalopodous Mollusca. Among the Brachiopods are Terebratula digona (Fig. 113) and T. spinosa. Among the Gasteropoda the Pleurotomaria conoidea is remarkable from its elegant shape and markings, and very unlike any of the living Pleurotoma as represented by P. Babylonia (Fig. 114). Ostrea Marshii and Lima proboscidea, which belong to the Acephala, are fossil Mollusca of this epoch, to which also belong Entalophora cellarioides, Eschara Ranviliana, Bidiastopora cervicornis; elegant and characteristic molluscous Polyzoa. We give a representation of two living species, as exhibiting the form of these curious beings. (Figs. 115 and 116.)

Fig. 114.—Pleurotoma Babylonia. (Recent.)

The Echinoderms and Polyps appear in great numbers in the deposits of the Lower Oolite: Apiocrinus elegans, Hyboclypus gibberulus, Dysaster Endesii represent the first; Montlivaltia caryophyllata, Anabacia orbulites, Cryptocœnia bacciformis, and Eunomia radiata represent the second.

Fig. 115.—Adeona folifera. (Recent Polyzoa.)

Fig. 116.—Cellaria loriculata. (Recent Polyzoa.)

This last and most remarkable species of Zoophyte presents itself in great masses many yards in circumference, and necessitates a long period of time for its production. This assemblage of little creatures living under the waters but only at a small depth beneath the surface, as Mr. Darwin has demonstrated, has nevertheless produced banks, or rather islets, of considerable extent, which at one time constituted veritable reefs rising out of the ocean. These reefs were principally constructed in the Jurassic period, and their extreme abundance is one of the characteristics of this geological age. The same phenomenon continues in our day, but by the agency of a new race of zoophytes, which carry on their operations, preparing a new continent, probably, in the atolls of the Pacific Ocean. (See Fig. 108, p. 240.)

Fig. 117. 1, Otopteris dubia; 2, Otopteris obtusa; 3, Otopteris acuminata; 4, Otopteris cuneata.

The flora of the epoch was very rich. The Ferns continue to exist, but their size and bearing were sensibly inferior to what they had been in the preceding period. Among them Otopteris, distinguished for its simply pinnated leaves, whose leaflets are auriculate at the base: of the five species, 1, O. dubia; and 2, O. obtusa; and 3, O. acuminata; and 4, O. cuneata (Fig. 117), are from the Oolite. In addition to these we may name Coniopteris Murrayana, Pecopteris Desnoyersii, Pachypteris lanceolata, and Phlebopteris Phillipsii; and among the Lycopods, Lycopodus falcatus.

The vegetation of this epoch has a peculiar facies, from the presence of the family of the Pandanaceæ, or screw-pines, so remarkable for their aërial roots, and for the magnificent tuft of leaves which terminates their branches. Neither the leaves nor the roots of these plants have, however, been found in the fossil state, but we possess specimens of their large and spherical fruit, which leave no room for doubt as to the nature of the entire plant.

The Cycads were still represented by the Zamias, and by many species of Pterophyllum. The Conifers, that grand family of recent times, to which the pines, firs, and other trees of our northern forests belong, began to occupy an important part in the world’s vegetation from this epoch. The earliest Conifers belonged to the genera Thuites, Taxites, and Brachyphyllum. The Thuites were true Thuyas, evergreen trees of the present epoch, with compressed branches, small imbricated and serrated leaves, somewhat resembling those of the Cypress, but distinguished by many points of special organisation. The Taxites have been referred, with some doubts, to the Yews. Finally, the Brachyphyllum were trees which, according to the characteristics of their vegetation, seem to have approached nearly to two existing genera, the Arthotaxis of Tasmania, and the Weddringtonias of South Africa. The leaves of the Brachyphyllum are short and fleshy, with a large and rhomboidal base.

Lower Oolite Rocks.

The formation which represents the Lower Oolite, and which in England attains an average thickness of from 500 to 600 feet, forms a very complex system of stratification, which includes the two formations, Bajocien and Bathonian, adopted by M. D’Orbigny and his followers. The lowest beds of the Inferior Oolite occur in Normandy, in the Lower Alps (Basses-Alpes), in the neighbourhoods of Lyons and Neuchatel. They are remarkable near Bayeux for the variety and beauty of their fossils: the rocks are composed principally of limestones—yellowish-brown, or red, charged with hydrated oxide of iron, often oolitic, and reposing on calcareous sands. These deposits are surmounted by alternate layers of clay and marl, blue or yellow—the well-known Fuller’s Earth, which is so called from its use in the manufacture of woollen fabrics to extract the grease from the wool. The second series of the Lower Oolite, which attains a thickness of from 150 to 200 feet on the coast of Normandy, and is well developed in the neighbourhood of Caen and in the Jura, has been divided, in Britain, into four formations, in an ascending scale:—

1. The Great or Bath Oolite, which consists principally of a very characteristic, fine-grained, white, soft, and well-developed oolitic limestone, at Bath, and also at Caen in Normandy. At the base of the Great Oolite the Stonesfield beds occur, in which were found the bones of the marsupial Mammals, to which we have already alluded; and along with them bones of Reptiles, principally Pterodactyles, together with some finely-preserved fossil plants, fruits, and insects.

2. Bradford Clay, which is a bluish marl, containing many fine Encrinites (commonly called stone-lilies), but which had only a local existence, appearing to be almost entirely confined to this formation. “In this case, however,” says Lyell, “it appears that the solid upper surface of the ‘Great Oolite’ had supported, for a time, a thick submarine forest of these beautiful Zoophytes, until the clear and still water was invaded with a current charged with mud, which threw down the stone-lilies, and broke most of their stems short off near the point of attachment. The stumps still remain in their original position.”[65] See Fig. 1, Plate XIX., p. 261. (Bradford, or Pear, Encrinite.)

3. Forest Marble, which consists of an argillaceous shelly limestone, abounding in marine fossils, and sandy and quartzose marls, is quarried in the forest of Wichwood, in Wiltshire, and in the counties of Dorset, Wilts, and Somerset.

4. The Cornbrash (wheat-lands) consists of beds of rubbly cream-coloured limestone, which forms a soil particularly favourable to the cultivation of cereals; hence its name.[66]

The Lower Oolite ranges across the greater part of England, but “attains its maximum development near Cheltenham, where it can be subdivided, at least, into three parts. Passing north, the two lower divisions, each more or less characterised by its own fossils, disappear, and the Ragstone north-east of Cheltenham lies directly upon the Lias; apparently as conformably as if it formed its true and immediate successor, while at Dundry the equivalents of the upper freestones and ragstones (the lower beds being absent) lie directly on the exceedingly thin sands, which there overlie the Lower Lias. In Dorsetshire, on the coast, the series is again perfect, though thin. Near Chipping Norton, in Oxfordshire, the Inferior Oolite disappears altogether, and the Great Oolite, having first overlapped the Fullers’ Earth, passes across the Inferior Oolite, and in its turn seems to lie on the Upper Lias with a regularity as perfect as if no formation in the neighbourhood came between them. In Yorkshire the changed type of the Inferior Oolite, the prevalence of sands, land-plants, and beds of coal, occur in such a manner as to leave no doubt of the presence of terrestrial surfaces on which the plants grew, and all these phenomena lead to the conclusion that various and considerable oscillations of level took place in the British area during the deposition of the strata, both of the Inferior Oolite and of the formations which immediately succeed it.”[67]

Fig. 118.—Meandrina Dædalæa. a, entire figure, reduced; b, portion, natural size. (Recent Coral.)

The Inferior Oolite here alluded to is a thin bed of calcareous freestone, resting on, and sometimes replaced by yellow sand, which constitutes the passage-beds from the Liassic series. The Fullers’ Earth clay lies between the limestones of the Inferior and Great Oolite, at the base of which last lies the Stonesfield slate—a slightly oolitic, shelly limestone, or flaggy and fissile sandstone, some six feet thick, rich in organic remains, and ranging through Oxfordshire towards the north-east, into Northamptonshire and Yorkshire. At Colley Weston, in Northamptonshire, fossils of Pecopteris polypodioides are found. In the Great Oolite formation, near Bath, are many corals, among which the Eunomia radiata is very conspicuous. The fossil is not unlike the existing brain-coral of the tropical seas (Fig. 118). The work of this coral seems to have been suddenly stopped by “an invasion,” says Lyell, “of argillaceous matter, which probably put a sudden stop to the growth of Bradford Encrinites, and led to their preservation in marine strata.”[68] The Cornbrash is, in general, a cream-coloured limestone, about forty feet thick, in the south-west of England, and occupying a considerable area in Dorsetshire and North Wilts, as at Cricklade, Malmesbury, and Chippenham, in the latter county. Terebratula obovata is its characteristic shell, and Nucleolites clunicularis, Lima gibbosa, and Avicula echinata occur constantly in great numbers. Wherever it occurs the Cornbrash affords a rich and fertile soil, well adapted for the growth of wheat, while the Forest Marble, as a soil, is generally poor. The Cornbrash passes downwards into the Forest Marble, and sometimes, as at Bradford, near Bath, is replaced by clay. This clay, called the Bradford clay, is almost wholly confined to the county of Wilts. Terebratula decussata is one of the most characteristic fossils, but the most common is the Apiocrinites or pear-shaped encrinite, whose remains in this clay are so perfectly preserved that the most minute articulations are often found in their natural positions. Plate XIX., p. 261 (Fig. 1), represents an adult attached by a solid base to the rocky bottom on which it grew, whilst the smaller individuals show the Encrinite in its young state—one with arms expanded, the other with them closed. Ripple-marked slabs of fissile Forest Marble are used as a roofing-slate, and may be traced over a broad band of country in Wiltshire and Gloucestershire, separated from each other by thin seams of clay, in which the undulating ridges of the sand are preserved, and even the footmarks of small Crustaceans are still visible.

XVII.—Ideal Landscape of the Lower Oolite Period.

On the opposite page (Plate XVII.) is represented an ideal landscape of the period of the Lower Oolite. On the shore are types of the vegetation of the period. The Zamites, with large trunk covered with fan-like leaves, resembled in form and bearing the existing Zamias of tropical regions; a Pterophyllum, with its stem covered from base to summit with its finely-cut feathery leaves; Conifers closely resembling our Cypress, and an arborescent Fern. What distinguishes this sub-period from that of the Lias is a group of magnificent trees, Pandanus, remarkable for their aërial roots, their long leaves, and globular fruit.

Upon one of the trees of this group the artist has placed the Phascolotherium, not very unlike to our Opossum. It was amongst the first of the Mammalia which appeared in the ancient world. The artist has here enlarged the dimensions of the animal in order to show its form. Let the reader reduce it in imagination one-sixth, for it was not larger than an ordinary-sized cat.

A Crocodile and the fleshless skeleton of the Ichthyosaurus remind us that Reptiles still occupied an important place in the animal creation. A few Insects, especially Dragon-flies, fly about in the air. Ammonites float on the surface of the waves, and the terrible Plesiosaurus, like a gigantic swan, swims about in the sea. The circular reef of coral, the work of ancient Polyps, foreshadows the atolls of the great ocean, for it was during the Jurassic period that the Polyps of the ancient world were most active in the production of coral-reefs and islets.

Middle Oolite.

The terrestrial flora of this age was composed of Ferns, Cycads, and Conifers. The first represented by the Pachypteris microphylla, the second by Zamites Moreana. Brachyphyllum Moreanum and B. majus appear to have been the Conifers most characteristic of the period; fruits have also been found in the rocks of the period, which appear to belong to Palms, but this point is still obscure and doubtful.

Numerous vestiges of the fauna which animated the period are also revealed in the rocks of this age. Certain hemipterous insects appear on the earth for the first time, and the Bees among the Hymenoptera, Butterflies among the Lepidoptera, and Dragon-flies among the Neuroptera. In the bosom of the ocean, or upon its banks, roamed the Ichthyosaurus, Ceteosaurus, Pterodactylus crassirostris, and the Geosaurus; the latter being very imperfectly known.

The Ceteosaurus whose bones have been discovered in the upper beds of the Great Oolite at Enslow Rocks, at the Kirtlington Railway Station, north of Oxford, and some other places, was a species of Crocodile nearly resembling the modern Gavial or Crocodile of the Ganges. This huge whale-like reptile has been described by Professor John Phillips as unmatched in size and strength by any of the largest inhabitants of the Mesozoic land or sea—perhaps the largest animal that ever walked upon the earth. A full-grown Ceteosaurus must have been at least fifty feet long, ten feet high, and of a proportionate bulk. In its habits it was, probably, a marsh-loving or river-side animal, dwelling amidst filicene, cycadaceous, and coniferous shrubs and trees full of insects and small mammalia. The one small and imperfect tooth which has been found resembles that of Iguanodon more than of any other reptile; and it seems probable that the Ceteosaurus was nourished by vegetable food, which abounded in the vicinity of its haunts, and was not obliged to contend with the Megalosaurus for a scanty supply of more stimulating diet.[69]

Fig. 119.—Ramphorynchus restored. One-quarter natural size.

Another reptile allied to the Pterodactyle lived in this epoch—the Ramphorynchus, distinguished from the Pterodactyle by a long tail. The imprints which this curious animal has left upon the sandstone of the period are impressions of its feet and the linear furrow made by its tail. Like the Pterodactyle, the Ramphorynchus, which was about the size of a crow, could not precisely fly, but, aided by the wing (a sort of natural parachute formed by the membrane connecting the fingers with the body), it could throw itself from a height upon its prey. Fig. 119 represents a restoration of this animal. The footprints in the soil are in imitation of those which accompany the remains of the Ramphorynchus in the Oolitic rocks, and they show the imprints of the anterior and posterior feet and also the marks made by the tail.

This tail was very long, far surpassing in length the rest of the vertebral column, and consisting of more than thirty vertebræ—which were at first short, but rapidly elongate, retain their length for a considerable distance, and then gradually diminish in size.

XVIII.—Ideal landscape of the Middle Oolitic Period.

Another genus of Reptiles appears in the Middle Oolite, of which we have had a glimpse in the Lias and Great Oolite of the preceding section. This is the Teleosaurus, which the recent investigations of M. E. Deslongchamps allow of re-construction. The Teleosaurus enables us to form a pretty exact idea of these Crocodiles of the ancient seas—these cuirassed Reptiles, which the German geologist Cotta describes as “the great barons of the kingdom of Neptune, armed to the teeth, and clothed in an impenetrable panoply; the true filibusters of the primitive seas.”

The Teleosaurus resembled the Gavials of India. The former inhabited the banks of rivers, perhaps the sea itself; they were longer, more slender, and more active than the living species; they were about thirty feet in length, of which the head may be from three to four feet, with their enormous jaws sometimes with an opening of six feet, through which they could engulf, in the depths of their enormous throat, animals of considerable size.

The Teleosaurus cadomensis is represented on the opposite page (Plate XVIII.), after the sketch of M. E. Deslongchamps, carrying from the sea in its mouth a Geoteuthis, a species of Calamary of the Oolitic epoch. This creature was coated with a cuirass both on the back and belly. In order to show this peculiarity, a living individual is represented on the shore, and a dead one is floating on its back in shallow water, leaving the ventral cuirass exposed.

Behind the Teleosaurus cadomensis in the engraving, another Saurian, the Hylæosaurus, is represented, which makes its appearance in the Cretaceous epoch. We have here adopted the restoration which has been so ably executed by Mr. Waterhouse Hawkins, at the Crystal Palace, Sydenham.

Fig. 120.—Eryon arctiformis.

Besides the numerous Fishes with which the Oolitic seas swarmed, they contained some Crustaceans, Cirripedes, and various genera of Mollusca and Zoophytes. Eryon arctiformis, represented in Fig. 119, belongs to the class of Crustaceans, of which the spiny lobster is the type. Among the Mollusca were some Ammonites, Belemnites, and Oysters, of which many hundred species have been described. Of these we may mention Ammonites refractus, A. Jason and A. cordatus, Ostrea dilatata, Terebratula diphya, Diceras arietena, Belemnites hastatus, and B. Puzosianus. In some of the finely-laminated clays the Ammonites are very perfect, but somewhat compressed, with the outer lip or margin of the aperture entire (Fig. 120). Similar prolongations have been noticed in Belemnites found by Dr. Mantell in the Oxford Clay, near Chippenham.

Fig. 121.—Perfect Ammonite.

XIX.—Fig. 1.—Apiocrinites rotundus. Fig. 2.—Encrinus liliiformis.

Among the Echinoderms, Cidaris glandiferus, Apiocrinus Roissyanus, and A. rotundus, the graceful Saccocoma pectinata, Millericrinus nodotianus, Comatula costata, and Hemicidaris crenularis may be mentioned; Apiocrinites rotundus, figured in Plate XIX., is a reduced restoration: 1, being expanded; a, closed; 3, a cross section of the upper extremity of the pear-shaped head; 4, a vertical section showing the enlargement of the alimentary canal, with the hollow lenticular spaces which descend through the axis of the column, forming the joints, and giving elasticity and flexure to the whole stem, without risk of dislocation. A. rotundus is found at Bradford in Wiltshire, Abbotsbury in Dorset, at Soissons, and Rochelle. This species—known as the Bradford Pear-Encrinite—is only found in the strata mentioned.

The Corals of this epoch occur in great abundance. We have already remarked that these aggregations of Polyps are often met with at a great depth in the strata. These small calcareous structures have been formed in the ancient seas, and the same phenomenon is extending the terrestrial surface in our days in the seas of Oceania, where reefs and atolls of coral are rising by slow and imperceptible steps, but with no less certainty. Although their mode of production must always remain to some extent a mystery, the investigations of M. Lamaroux, Mr. Charles Darwin, and M. D’Orbigny have gone a long way towards explaining their operations; for the Zoophyte in action is an aggregation of these minute Polyps. Describing what he believes to be a sea-pen, a Zoophyte allied to Virgularia Patagonia, Mr. Darwin says: “It consists of a thin, straight, fleshy stem, with alternate rows of polypi on each side, and surrounding an elastic stony axis. The stem at one extremity is truncate, but at the other is terminated by a vermiform fleshy appendage. The stony axis which gives strength to the stem, may be traced at this extremity into a mere vessel filled with granular matter. At low water hundreds of these zoophytes might be seen, projecting like stubble, with the truncate end upwards, a few inches above the surface of the muddy sand. When touched or pulled, they drew themselves in suddenly, with force, so as nearly or quite to disappear. By this action, the highly-elastic axis must be bent at the lower extremity, where it is naturally slightly curved; and I imagine it is by this elasticity alone that the zoophyte is enabled to rise again through the mud. Each polypus, though closely united to its brethren, has a distinct mouth, body, and tentacula. Of these polypi, in a large specimen there must be many thousands. Yet we see that they act by one movement; that they have one central axis, connected with a system of obscure circulation.” Such is the brief account given by a very acute observer of these singular beings. They secrete the calcareous matter held in solution in the oceanic waters, and produce the wonderful structures we have now under consideration; and these calcareous banks have been in course of formation during many geological ages. They just reach the level of the waters, for the polyps perish as soon as they are so far above the surface that neither the waves nor the flow of the tides can reach them. In the Oolitic rocks these banks are frequently found from twelve to fifteen feet thick, and many leagues in length, and preserving, for the most part, the relative positions which they occupied in the sea while in course of formation.

The rocks which now represent the Middle Oolitic Period are usually divided into the Oxford Clay, the lower member of which is an arenaceous limestone, known as the Kellaways Rock, which in Wiltshire and other parts of the south-west of England attains a thickness of eight or ten feet, with the impressions of numerous Ammonites, and other shells. In Yorkshire, around Scarborough, it reaches the thickness of thirty feet; and forms well-developed beds of bluish-black marl in the department of Calvados, in France. It is the base of this clay which forms the soil (Argile de Dives) of the valley of the Auge, renowned for its rich pasturages and magnificent cattle. The same beds form the base of the oddly-shaped but fine rocks of La Manche, which are popularly known as the Vaches Noires (or black cows)—a locality celebrated, also, for its fine Ammonites transformed into pyrites.

The Oxford Clay constitutes the base of the hills in the neighbourhood of Oxford, forming a bed of clay sometimes more than 600 feet thick. It is found well-developed in France, at Trouville, in the department of the Calvados; and at Neuvisy, in the department of the Ardennes, where it attains a thickness of about 300 feet. It is a bluish, sometimes whitish limestone (often argillaceous), and bluish marl. The Gryphæa dilatata is the most common fossil in the Oxford Clay. The Coral Rag is so called from the fact that the limestone of which it is chiefly composed consists, in part, of an aggregation of considerable masses of petrified Corals; not unlike those now existing in the Pacific Ocean, supposing them to be covered up for ages and fossilised. This coral stratum extends through the hills of Berkshire and North Wilts, and it occurs again near Scarborough. In the counties of Dorset, Bedford, Buckingham, and Cambridge, and some other parts of England, the limestone of the Coral Rag disappears and is replaced by clay—in which case the Oxford Clay is overlaid directly by the Kimeridge Clay. In France it is found in the departments of the Meuse, of the Yonne, of the Ain, of the Charente Inférieure. In the Alps the Diceras limestone is regarded, by most geologists, as coeval with the English Coral Rag.

Upper Oolite.

Some marsupial Mammals have left their remains in the Upper Oolite as in the Lower. They belong to the genus Sphalacotherium. Besides the Plesiosauri and Teleosauri, there still lived in the maritime regions a Crocodile, the Macrorhynchus; and the monstrous Pœcilopleuron, with sharp cutting teeth, one of the most formidable animals of this epoch; the Hylæosaurus, Cetiosaurus, Stenosaurus, and Streptospondylus, and among the Turtles, the Emys and Platemys. As in the Lower Oolite, so also in the Upper, Insects similar to those by which we are surrounded, pursued their flight in the meadows and hovered over the surface of the water. Of these, however, too little is known for us to give any very precise indication on the subject of their special organisation.

Fig. 122.—Bird of Solenhofen (Archæopteryx).

The most remarkable fact relating to this period is the appearance of the first bird. Hitherto the Mammals, and of these only imperfectly-organised species, namely, the Marsupials, have alone appeared. It is interesting to witness birds appearing immediately after. In the quarries of lithographic stone at Solenhofen, the remains of a bird, with feet and feathers, have been found, but without the head. These curious remains are represented in Fig. 122, in the position in which they were discovered. The bird is usually designated the Bird of Solenhofen.

Fig. 123. Shell of Physa fontinalis.

The Oolitic seas of this series contained Fishes belonging to the genera Asteracanthus, Strephodes, Lepidotus, and Microdon. The Cephalopodous Mollusca were not numerous, the predominating genera belonging to the Lamellibranchs and to the Gasteropods, which lived on the shore. The reef-making Madrepores or Corals were more numerous. A few Zoophytes in the fossil state testify to the existence of these extraordinary animals. The fossils characteristic of the fauna of the period include Ammonites decipiens and A. giganteus, Natica elegans and hemispherica, Ostrea deltoidea and O. virgula, Trigonia gibbosa, Pholadomya multicostata and P. acuticostata, Terebratula subsella, and Hemicidaris Purbeckensis. Some Fishes, Turtles, Paludina, Physa (Fig. 123), Unio, Planorbis (Fig. 201), and the little crustacean bivalves, the Cypris, constituted the fresh-water fauna of the period.

The terrestrial flora of the period consisted of Ferns, Cycadeaceæ, and Conifers; in the ponds and swamps some Zosteræ. The Zosteræ are monocotyledonous plants of the family of the Naïdaceæ, which grow in the sandy mud of maritime regions, forming there, with their long, narrow, and ribbon-like leaves, vast prairies of the most beautiful green. At low tides these masses of verdure appear somewhat exposed. They would form a retreat for a great number of marine animals, and afford nourishment to others.

XX.—Ideal Landscape of the Upper Oolitic Period.

On the opposite page an ideal landscape of the period (Plate XX.) represents some of the features of the Upper Oolite, especially the vegetation of the Jurassic period. The Sphenophyllum, among the Tree-ferns, is predominant in this vegetation; some Pandanas, a few Zamites, and many Conifers, but we perceive no Palms. A coral islet rises out of the sea, having somewhat of the form of the atolls of Oceania, indicating the importance these formations assumed in the Jurassic period. The animals represented are the Crocodileimus of Jourdan, the Ramphorynchus, with the imprints which characterise its footsteps, and some of the invertebrated animals of the period, as the Asteria, Comatula, Hemicidaris, Pteroceras. Aloft in the air floats the bird of Solenhofen, the Archæopteryx, which has been re-constructed from the skeleton, with the exception of the head, which remains undiscovered.

The rocks which represent the Upper Oolite are usually divided into two series: 1. The Purbeck Beds; 2. The Portland Stone and Sand; and 3. The Kimeridge Clay.

The Kimeridge Clay, which in many respects bears a remarkable resemblance to the Oxford Clay, is composed of blue or yellowish argillaceous beds, which occur in the state of clay and shale (containing locally beds of bituminous schist, sometimes forming a sort of earthy impure coal), and several hundred feet in thickness. These beds are well developed at Kimeridge, in Dorsetshire, whence the clay takes its name. In some parts of Wiltshire the beds of bituminous matter have a shaly appearance, but there is an absence of the impressions of plants which usually accompany the bitumen, derived from the decomposition of plants. These rocks, with their characteristic fossils, Cardium striatulum and Ostrea deltoidea, are found throughout England: in France, at Tonnerre, Dept. Yonne; at Havre; at Honfleur; at Mauvage; in the department of the Meuse it is so rich in shells of Ostrea deltoidea and O. virgula, that, “near Clermont in Argonne, a few leagues from St. Menehould,” says Lyell,[70] “where these indurated marls crop out from beneath the Gault, I have seen them (Gryphæa virgula) on decomposing leave the surface of every ploughed field literally strewed over with this fossil oyster.”

The second section of this series consists of the oolitic limestone of Portland, which is quarried in the Isle of Portland and in the cliffs of the Isle of Purbeck in Dorsetshire, and also at Chilmark in the Vale of Wardour, in Wiltshire. In France, the Portland beds are found near Boulogne, at Cirey-le-Château, Auxerre, and Gray (Haute Saône).

The Isle, or rather peninsula of Portland,[71] off the Dorsetshire coast, rises considerably above the sea-level, presenting on the side of the port a bold line of cliffs, connected with the mainland by the Chesil bank,[72] an extraordinary formation, consisting of a beach of shingle and pebbles loosely piled on the blue Kimeridge clay, and stretching ten miles westward along the coast. The quarries are chiefly situated in the northerly part of the island. The story told of this remarkable island is an epitome of the revolutions the surface of the earth has undergone. The slaty Purbeck beds which overlie the Portland stone are of a dark-yellowish colour; they are burnt in the neighbourhood for lime. The next bed is of a whiter and more lively colour. It is the stone of which the portico of St. Paul’s and many of the houses of London, built in Queen Anne’s time, were constructed. The building-stone contains fossils exclusively marine. Upon this stratum rests a bed of limestone formed in lacustrine waters. Finally, upon this bed rests another deposit of a substance which consists of very well-preserved vegetable earth or humus, quite analogous to our vegetable soil, of the thickness of from fifteen to eighteen inches, and of a blackish colour; it contains a strong proportion of carbonaceous earth; it abounds in the silicified remains of Conifers and other plants, analogous to the Zamia and Cycas—this soil is known as the “dirt-bed.” The trunks of great numbers of silicified trees and tropical plants are found here erect, their roots fixed in the soil, and of species differing from any of our forest trees. “The ruins of a forest upon the ruins of a sea,” says Esquiros, “the trunks of these trees were petrified while still growing. The region now occupied by the narrow channel and its environs had been at first a sea, in whose bed the Oolitic deposits which now form the Portland stone accumulated: the bed of the sea gradually rose and emerged from the waves. Upon the land thus rescued from the deep, plants began to grow; they now constitute with their ruins the soil of the dirt-bed. This soil, with its forest of trees, was afterwards plunged again into the waters—not the bitter waters of the ocean, but in the fresh waters of a lake formed at the mouth of some great river.”

Time passed on, however; a calcareous sediment brought from the interior by the waters, formed a layer of mud over the dirt-bed; finally, the whole region was covered by a succession of calcareous deposits, until the day when the Isle of Portland was again revealed to light. “From the facts observed,” says Lyell, “we may infer:—1. That those beds of the Upper Oolite, called the Portland, which are full of marine shells, were overspread with fluviatile mud, which became dry land, and covered with a forest, throughout a portion of space now occupied by the south of England, the climate being such as to admit of the growth of the Zamia and Cycas. 2. This land at length sank down and was submerged with its forest beneath a body of fresh water from which sediment was thrown down enveloping fluviatile shells. 3. The regular and uniform preservation of this thin bed of black earth over a distance of many miles, shows that the change from dry land to the state of a fresh-water lake, or estuary, was not accompanied by any violent denudation or rush of water, since the loose black earth, together with the trees which lay prostrate on its surface, must inevitably have been swept away had any such violent catastrophe taken place.”[73]

Fig. 124.—Geological humus. a, Fresh-water calcareous slate (Purbeck); b, Dirt-bed, with roots and stems of trees; c, Fresh-water beds; d, Portland Stone.

The soil known as the dirt-bed is nearly horizontal in the Isle of Portland; but we discover it again not far from there in the sea-cliffs of the Isle of Purbeck, having an inclination of 45°, where the trunks continue perfectly parallel among themselves, affording a fine example of a change in the position of beds originally horizontal. Fig. 124 represents this species of geological humus. “Each dirt-bed” says Sir Charles Lyell, “may, no doubt, be the memorial of many thousand years or centuries, because we find that two or three feet of vegetable soil is the only monument which many a tropical forest has left of its existence ever since the ground on which it now stands was first covered with its shade.”[74]

This bed of vegetable soil is, then, near the summit of that long and complicated series of beds which constitute the Jurassic period; these ruins, still vegetable, remind us forcibly of the coal-beds, for they are nothing else than a less advanced state of that kind of vegetable fossilisation which was perfected on such an immense scale, and during an infinite length of time in the coal period.

The Purbeck beds, which are sometimes subdivided into Lower, Middle, and Upper, are mostly fresh-water formations, intimately connected with the Upper Portland beds. But there they begin and end, being scarcely recognisable except in Dorsetshire, in the sea-cliffs of which they were first studied. They are finely exposed in Durdlestone Bay, near Swanage, and at Lulworth Cove, on the same coast. The lower beds consist of a purely fresh-water marl, eighty feet thick, containing shells of Cypris, Limnæa, and some Serpulæ in a bed of marl of brackish-water origin, and some Cypris-bearing shales, strangely broken up at the west end of the Isle of Purbeck.

The Middle series consists of twelve feet of marine strata known as the “cinder-beds,” formed of a vast accumulation of Ostrea distorta, resting on fresh-water strata full of Cypris fasciculata, Planorbis, and Limnæa, by which this strata has been identified as far inland as the vale of Wardour in Wiltshire. Above the cinder-beds are shales and limestones, partly of fresh-water and partly of brackish-water origin, in which are Fishes, many species of Lepidotus, and the crocodilian reptile, Macrorhynchus. On this rests a purely marine deposit, with Pecten, Avicula, &c. Above, again, are brackish beds with Cyrena, overlying which is thirty feet of fresh-water limestone, with Fishes, Turtles, and Cyprides.

The upper beds are purely fresh-water strata, about fifty feet thick, containing Paludina, Physa, Limnæa, all very abundant. In these beds the Purbeck marble, formerly much used in the ornamental architecture of the old English cathedrals, was formerly quarried. (See Note, page 274.)

A few words may be added, in explanation of the term oolite, applied to this sub-period of the Jurassic formation. In a great number of rocks of this series the elements are neither crystalline nor amorphous—they are, as we have already said, oolitic; that is to say, the mass has the form of the roe of certain fishes. The question naturally enough arises, Whence this singular oolitic structure assumed by the components of certain rocks? It is asserted that the grinding action of the sea acting upon the precipitated limestone produces rounded forms analogous to grains of sand. This hypothesis may be well founded in some cases. The marine sediments which are deposited in some of the warm bays of Teneriffe are found to take the spheroidal granulated form of the oolite. But these local facts cannot be made to apply to the whole extent of the oolitic formations. We must, therefore, look further for an explanation of the phenomena.

It is admitted that if the cascades of Tivoli, for example, can give birth to the oolitic grains, the same thing happens in the quietest basins, that in stalactite-caverns oolitic grains develop themselves, which afterwards, becoming cemented together from the continued, but very slow, affluence of the calcareous waters, give rise to certain kinds of oolitic rocks.

On the other hand, it is known that nodules, more or less large, develop themselves in marls in consequence of the concentration of the calcareous elements, without the possibility of any wearing action of water. Now, as there exists every gradation of size between the smallest oolitic grains and the largest concretions, it is reasonable to suppose that the oolites are equally the product of concentration.

Finally, from research to research, it is found that perfectly constituted oolites—that is to say, concentric layers, as in the Jurassic limestone—develop themselves in vegetable earth in places where the effects of water in motion is not more admissible than in the preceding instances.

Thus we arrive at the conclusion, that if Nature sometimes forms crystals with perfect terminations in magmas in the course of solidification, she gives rise also to spheroidal forms surrounding various centres, which sometimes originate spontaneously, and in other cases are accumulated round the débris of fossils, or even mere grains of sand. Nevertheless, all mineral substances are not alike calculated to produce oolitic rocks; putting aside some particular cases, this property is confined to limestone and oxide of iron.

With regard to the distribution of the Jurassic formation on the terrestrial globe, it may be stated that the Cotteswold Hills in England, and in France the Jura mountains, are almost entirely composed of these rocks, the several series of beds being all represented in them—this circumstance, in fact, induced Von Humboldt to name the formation after this latter range. The Upper Lias also exists in the Pyrenees and in the Alps; in Spain; in many parts of Northern Italy; in Russia, especially in the government of Moscow, and in the Crimea; but it is in Germany where it occupies the most important place. A thin bed of oolitic limestone presents, at Solenhofen in Bavaria, a geological repository of great celebrity, containing fossil Plants, Fishes, Insects, Crustaceans, with some Pterodactyles, admirably preserved; it yielded also some of the earliest of the feathered race. The fine quarries of lithographic stone at Pappenheim, so celebrated all over Europe, belong to the Jurassic formation.

It has recently been announced that these rocks have been found in India; they contribute largely to the formation of the main mass of the Himalayas, and to the chain of the Andes in South America; finally, from recent investigations, they seem to be present in New Zealand.

In England the Lias constitutes a well-defined belt about thirty miles broad, extending from Dorsetshire, in the south, to Yorkshire, in the north, formed of alternate beds of clay, shales, and limestone (with layers of jet), on the coast near Whitby. It is rich, as we have seen, in ancient life, and that in the strongest forms imaginable. From the unequal hardness of the rocks it comprises, it stands out boldly in some of the minor ranges of hills, adding greatly to the picturesque beauty of the scenery in the centre of the country. In Scotland the formation occupies a very limited space.

A map of the country at the close of the Jurassic period would probably show double the extent of dry land in the British Islands, compared with what it displayed as an island in the primordial ocean; but Devon and Cornwall had long risen from the sea, and it is probable that the Jurassic beds of Dorsetshire and France were connected by a tongue of land running from Cherbourg to the Liassic beds of Dorsetshire, and that Boulogne, still an island, was similarly connected with the Weald.

Fig. 125.—Crioceras Duvallii, Sowerby. A non-involuted Ammonite. (Neocomian.)

These sections, published by the Geological Survey, show in detail the beds in their regular and natural order of succession, with the thickness, mineral character, and contents, as well as the fossils, of each separate bed.

THE CRETACEOUS PERIOD.

The name Cretaceous (from creta, chalk) is given to this epoch in the history of our globe because the rocks deposited by the sea, towards its close, are almost entirely composed of chalk (carbonate of lime).

Carbonate of lime, however, does not now appear for the first time as a part of the earth’s crust; we have already seen limestone occurring, among the terrestrial materials, from the Silurian period; the Jurassic formation is largely composed of carbonate of lime in many of its beds, which are enormous in number as well as extent; it appears, therefore, that in the period called Cretaceous by geologists, carbonate of lime was no new substance in the constitution of the globe. If geologists have been led to give this name to the period, it is because it accords better than any other with the characteristics of the period; with the vast accumulations of chalky or earthy limestone in the Paris basin, and the beds of so-called Greensand, and Chalk of the same age, so largely developed in England.

We have already endeavoured to establish the origin of lime, in speaking of the Silurian and Devonian periods, but it may be useful to recapitulate the explanation here, even at the risk of repeating ourselves.

We have said that lime was, in all probability, introduced to the globe by thermal waters flowing abundantly through the fissures, dislocations, and fractures in the ground, which were themselves caused by the gradual cooling of the globe; the central nucleus being the grand reservoir and source of the materials which form the solid crust. In the same manner, therefore, as the several eruptive substances—such as granites, porphyries, trachytes, basalts, and lava—have been ejected, so have thermal waters charged with carbonate of lime, and often accompanied by silica, found their way to the surface in great abundance, through the fissures, fractures, and dislocations in the crust of the earth. We need only mention here the Iceland geysers, the springs of Plombières, and the well-known thermal springs of Bath and elsewhere in this country.

But how comes lime in a state of bicarbonate, dissolved in these thermal waters, to form rocks? That is what we propose to explain.

During the primary geological periods, thermal waters, as they reached the surface, were discharged into the sea and united themselves with the waves of the vast primordial ocean, and the waters of the sea became sensibly calcareous—they contained, it is believed, from one to two per cent. of lime. The innumerable animals, especially Zoophytes, and Mollusca with solid shells, with which the ancient seas swarmed, secreted this lime, out of which they built up their mineral dwelling—or shell. In this liquid and chemically calcareous medium, the Foraminifera and Polyps of all forms swarmed, forming an innumerable population. Now what became of the bodies of these creatures after death? They were of all sizes, but chiefly microscopic; that is, so small as to be individually all but invisible to the naked eye. The perishable animal matter disappeared in the bosom of the waters by decomposition, but there still remained behind the indestructible inorganic matter, that is to say, the carbonate of lime forming their testaceous covering; these calcareous deposits accumulating in thick beds at the bottom of the sea, became compacted into a solid mass, and formed a series of continuous beds superimposed on each other. These, increasing imperceptibly in the course of ages, ultimately formed the rocks of the Cretaceous period, which we have now under consideration.

These statements are not, as the reader might conceive from their nature, a romantic conception invented to please the imagination of those in search of a system—the time is past when geology should be regarded as the romance of Nature—nor has what we advance at all the character of an arbitrary conception. One is no doubt struck with surprise on learning, for the first time, that all the limestone rocks, all the calcareous stones employed in the construction of our dwellings, our cities, our castles and cathedrals, were deposited in the seas of an earlier world, and are only composed of an aggregation of shells of Mollusca, or fragments of the testaceous coverings of Foraminifera and other Zoophytes—nay, that they were secreted from the water itself, and then assimilated by these minute creatures, and that this would appear to have been the great object of their creation in such myriads. Whoever will take the trouble to observe, and reflect on what he observes, will find all his doubts vanish. If chalk be examined with a microscope, it will be found to be composed of the remains of numerous Zoophytes, of minute and divers kinds of shells, and, above all, of Foraminifera, so small that their very minuteness seems to have rendered them indestructible. A hundred and fifty of these small beings placed end to end, in a line, will only occupy the space of about one-twelfth part of an inch.

Chalk under the Microscope.

Fig. 126.—Chalk of Meudon (magnified).

Much of this curious information was unknown, or at least only suspected, when Ehrenberg began his microscopical investigations. From small samples of chalk reduced to powder, placed upon the object-glass, and examined under the microscope, Ehrenberg prepared the designs which we reproduce from his learned micrographical work, in which some of the elegant forms discovered in the Chalk are illustrated, greatly magnified. Fig. 126 represents the chalk of Meudon, in France, in which ammonite-like forms of Foraminifera and others, equally beautiful, appear. Fig. 127, from the chalk of Gravesend, contains similar objects. Fig. 128 is an example of chalk from the island of Moën, in Denmark; and Fig. 129, that which is found in the Tertiary rocks of Cattolica, in Sicily. In all these the shells of Ammonites appear, with clusters of round Foraminifera and other Zoophytes. In two of these engravings (Figs. 126 and 128), the chalk is represented in two modes—in the upper half, by transparency or transmitted light; in the lower half, the mass is exhibited by superficial or reflected light.

Chalk under the Microscope.

Fig. 127.—Chalk of Gravesend. (After Ehrenberg).—Magnified.

Observation, then, establishes the truth of the explanation we have given concerning the formation of the chalky or Cretaceous rocks; but the question still remains—How did these rocks, originally deposited in the sea, become elevated into hills of great height, with bold escarpments, like those known in England as the North and South Downs? The answer to this involves the consideration of other questions which have, at present, scarcely got beyond hypothesis.

Chalk under the Microscope.

Fig. 128.—Chalk of the Isle of Moën, Denmark.

During and after the deposition of the Portland and Purbeck beds, the entire Oolite Series, in the south and centre of England and other regions, was raised above the sea-level and became dry land. Above these Purbeck beds, as Professor Ramsay tells us [in the district known as the Weald], “we have a series of beds of clays, sandstones, and shelly limestones, indicating by their fossils that they were deposited in an estuary where fresh water and occasionally brackish water and marine conditions prevailed. The Wealden and Purbeck beds indeed represent the delta of an immense river which in size may have rivalled the Ganges, Mississippi, Amazon, &c., and whose waters carried down to its mouth the remains of land-plants, small Mammals, and great terrestrial Reptiles, and mingled them with the remains of Fishes, Molluscs, and other forms native to its waters. I do not say that this immense river was formed or supplied by the drainage of what we now call Great Britain—I do not indeed know where this continent lay, but I do know that England formed a part of it, and that in size it must have been larger than Europe, and was probably as large as Asia, or the great continent of America.” Speaking of the geographical extent of the Wealden, Sir Charles Lyell says: “It cannot be accurately laid down, because so much of it is concealed beneath the newer marine formations. It has been traced about 200 miles from west to east; from the coast of Dorsetshire to near Boulogne, in France; and nearly 200 miles from north-west to south-east, from Surrey and Hampshire to Beauvais, in France;”[75] but he expresses doubt, supposing the formation to have been continuous, if the two areas were contemporaneous, the region having undergone frequent changes, the great estuary having altered its form, and even shifted its place. Speaking of a hypothetical continent, Sir Charles Lyell says: “If it be asked where the continent was placed from the ruins of which the Wealden strata were derived, and by the drainage of which a great river was fed, we are half tempted to speculate on the former existence of the Atlantis of Plato. The story of the submergence of an ancient continent, however fabulous in history, must have been true again and again as a geological event.”[76]

Chalk under the Microscope.

Fig. 129.—Chalk of Cattolica, Sicily (magnified).

The proof that the Wealden series were accumulated under fresh-water conditions and as a river deposit[77] lies partly in the nature of the strata, but chiefly in the nature of the organic remains. The fish give no positive proof, but a number of Crocodilian reptiles give more conclusive evidence, together with the shells, most of them being of fresh-water origin, such as Paludina, Planorbis, Lymnæa, Physa, and such like, which are found living in many ponds and rivers of the present day. Now and then we find bands of marine remains, not mixed with fresh-water deposits, but interstratified with them; showing that at times the mouth and delta of the river had sunk a little, and that it had been invaded by the sea; then by gradual change it was lifted up, and became an extensive fresh-water area. This episode at last comes to an end by the complete submergence of the Wealden area; and upon these fresh-water strata a set of marine sands and clays, and upon these again thick beds of pure white earthy limestone of the Cretaceous period were deposited. The lowest of these formations is known as the Lower Greensand; then followed the clays of the Gault, which were succeeded by the Upper Greensand. Then, resting upon the Upper Greensand, comes the vast mass of Chalk which in England consists of soft white earthy limestone, containing, in the upper part, numerous bands of interstratified flints, which were mostly sponges originally, that have since become silicified and converted into flint. The strata of chalk where thickest are from 1,000 to 1,200 feet in thickness. Their upheaval into dry land brought this epoch to an end; the conditions which had contributed to its formation ceased in our area, and as the uppermost member of the Secondary rocks, it closes the record of Mesozoic times in England.

Let us add, to remove any remaining doubts, that in the basin of a modern European sea—the Baltic—a curious assemblage of phenomena, bearing on the question, is now in operation. The bed and coast-line of the Baltic continue slowly but unceasingly to rise, and have done so for several centuries, in consequence of the constant deposit which takes place of calcareous shells, added to the natural accumulations of sand and mud. The Baltic Sea will certainly be filled up in time by these deposits, and this modern phenomenon, which we find in progress, so to speak, brings directly under our observation an explanation of the manner in which the cretaceous rocks were produced in the ancient world, more especially when taken in connection with another branch of the same subject to which Sir Charles Lyell called attention, in an address to the Geological Society. It appears that just as the northern part of the Scandinavian continent is now rising, and while the middle part south of Stockholm remains unmoved, the southern extremity in Scania is sinking, or at least has sunk, within the historic period; from which he argues that there may have been a slow upheaval in one region, while the adjoining one was stationary, or in course of submergence.

After these explanations as to the manner in which the cretaceous rocks were formed, let us examine into the state of animal and vegetable life during this important period in the earth’s history.

The vegetable kingdom of this period forms an introduction to the vegetation of the present time. Placed at the close of the Secondary epoch, this vegetation prepares us for transition, as it were, to the vegetation of the Tertiary epoch, which, as we shall see, has a great affinity with that of our own times.

The landscapes of the ancient world have hitherto shown us some species of plants of forms strange and little known, which are now extinct. But during the period whose history we are tracing, the vegetable kingdom begins to fashion itself in a less mysterious manner; Palms appear, and among the regular species we recognise some which differ little from those of the tropics of our days. The dicotyledons increase slightly in number amid Ferns and Cycads, which have lost much of their importance in numbers and size; we observe an obvious increase in the dicotyledons of our own temperate climate, such as the alder, the wych-elm, the maple, and the walnut, &c.

“As we retire from the times of the primitive creation,” says Lecoq, “and slowly approach those of our own epoch, the sediments seem to withdraw themselves from the polar regions and restrict themselves to the temperate or equatorial zones. The great beds of sand and limestone, which constitute the Cretaceous formation, announce a state of things very different from that of the preceding ages. The seasons are no longer marked by indications of central heat; zones of latitude already show signs of their existence.

“Hitherto two classes of vegetation predominated: the cellular Cryptogams at first, the dicotyledonous Gymnosperms afterwards; and in the epoch which we have reached—the transition epoch of vegetation—the two classes which have reigned heretofore become enfeebled, and a third, the dicotyledonous Angiosperms, timidly take possession of the earth—they consist at first of a small number of species, and occupy only a small part of the soil, of which they afterwards take their full share; and in the succeeding periods, as in our own times, we shall see that their reign is firmly established; during the Cretaceous period, in short, we witness the appearance of the first dicotyledonous Angiosperms. Some arborescent Ferns still maintain their position, and the elegant Protopteris Singeri, Preissl., and P. Buvigneri, Brongn., still unfold their light fronds to the winds of this period. Some Pecopteri, differing from the Wealden species, live along with them. Some Zamites, Cycads, and Zamiostrobi announce that in the Cretaceous period the temperature was still high. New Palms show themselves, and, among others, Flabellaria chamæropifolia is especially remarkable for the majestic crown at its summit.

“The Conifers have endured better than the Cycadeæ; they formed then, as now, great forests, where Damarites, Cunninghamias, Araucarias, Eleoxylons, Abietites, and Pinites remind us of numerous forms still existing, but dispersed all over the earth.

“From this epoch date the Comptonias, attributed to the Myricaceæ; Almites Friesii, Nils., which we consider as one of the Betulaceæ; Carpinites arenaceus, Gœp., which is one of the Cupuliferæ; the Salicites, which are represented to us by the arborescent willows; the Acerinæ would have their Acerites cretaceæ, Nils., and the Juglanditæ, the Juglandites elegans, Gœp. But the most interesting botanical event of this period is the appearance of the Credneria, with its triple-veined leaves, of which no less than eight species have been found and described, but whose place in the systems of classification still remains uncertain. The Crednerias, like the Salicites, were certainly trees, as were most of the species of this remote epoch.”

In the following illustration are represented two of the Palms belonging to the Cretaceous period, restored from the imprints and fragments of the fossil remains left by the trunk and branches in the rocks of the period (Fig. 130.)

Fig. 130.—Fossil Palms restored.

But if the vegetation of the Cretaceous period exhibits sensible signs of approximation to that of our present era, we cannot say the same of the animal creation. The time has not yet come when Mammals analogous to those of our epoch gave animation to the forests, plains, and shores of the ancient world; even the Marsupial Mammals, which made their appearance in the Liassic and Oolitic formations, no longer exist, so far as is known, and no others of the class have taken their place. No climbing Opossum, with its young ones, appears among the leaves of the Zamites. The earth appears to be still tenanted by Reptiles, which alone break the solitudes of the woods and the silence of the valleys. The Reptiles, which seem to have swarmed in the seas of the Jurassic period, partook of the crocodilian organisation, and those of this period seem to bear more resemblance to the Lizards of our day. In this period the remains of certain forms indicate that they stood on higher legs; they no longer creep on the earth, and this is apparently the only approximation which seems to connect them more closely with higher forms.

It is not without surprise that we advert to the immense development, the extraordinary dimensions which the Saurian family attained at this epoch. These animals which, in our days, rarely exceed a yard or so in length, attained in the Cretaceous period as much as twenty. The marine lizard, which we notice under the name of Mosasaurus, was then the scourge of the seas, playing the part of the Ichthyosauri of the Jurassic period; for, from the age of the Lias to that of the Chalk, the Ichthyosauri, the Plesiosauri, and the Teleosauri were, judging from their organisation, the tyrants of the waters. They appear to have become extinct at the close of the Cretaceous period, and to give place to the Mosasaurus, to whom fell the formidable task of keeping within proper limits the exuberant production of the various tribes of Fishes and Crustaceans which inhabited the seas. This creature was first discovered in the celebrated rocks of St. Peter’s Mount at Maestricht, on the banks of the Meuse. The skull alone was about four feet in length, while the entire skeleton of Iguanodon Mantelli, discovered by Dr. Mantell in the Wealden strata, has since been met with in the Hastings beds of Tilgate Forest, measuring, as Professor Owen estimates, between fifty and sixty feet in length. These enormous Saurians disappear in their turn, to be replaced in the seas of the Tertiary epoch by the Cetaceans; and henceforth animal life begins to assume, more and more, the appearance it presents in the actually existing creation.

Seeing the great extent of the seas of the Cretaceous period, Fishes were necessarily numerous. The pike, salmon, and dory tribes, analogous to those of our days, lived in the seas of this period; they fled before the sharks and voracious dog-fishes, which now appeared in great numbers, after just showing themselves in the Oolitic period.

The sea was still full of Polyps, Sea-urchins, Crustaceans of various kinds, and many genera of Mollusca different from those of the Jurassic period; alongside of gigantic Lizards are whole piles of animalculæ—those Foraminifera whose remains are scattered in infinite profusion in the Chalk, over an enormous area and of immense thickness. The calcareous remains of these little beings, incalculable in number, have indeed covered, in all probability, a great part of the terrestrial surface. It will give a sufficient idea of the importance of the Cretaceous period in connection with these organisms to state that, in the rocks of the period, 268 genera of animals, hitherto unknown, and more than 5,000 species of special living beings have been found; the thickness of the rocks formed during the period being enormous. Where is the geologist who will venture to estimate the time occupied in creating and destroying the animated masses of which this formation is at once both the cemetery and the monument? For the purposes of description it will be convenient to divide the Cretaceous series into lower and upper, according to their relative ages and their peculiar fossils.

The Lower Cretaceous Period.

English equivalents. French classification.

Lower Greensand, upper part. Étage Aptien st.

Lower Greensand, lower part. „ Néocomien supérieur.

Weald clay and Hastings sands. „ Néocomien inférieur.

The Lower Wealden or Hastings Sand consists of sand, sandstone, and calciferous grit, clay, and shale, the argillaceous strata predominating. This part of the Wealden consists, in descending order, of:—

Feet.

Tunbridge Wells sand—Sandstone and loam 150

Wadhurst clay—Blue and brown shale and clay, with a little calc grit 100

Ashdown sands—Hard sand, with beds of calc grit 160

Ashburnham sands—Mottled, white, and red clay and sandstone 330

The Hastings sand has a hard bed of white sand in its upper part, whose steep natural cliffs produce the picturesque scenery of the “High rocks” of Hastings in Sussex.

Calcareous sandstone and grit, in which Dr. Mantell found the remains of the Iguanodon and Hylæosaurus, form an upper member of the Tunbridge Wells Sand. The formation extends over Hanover and Westphalia; the Wealden of these countries, according to Dr. Dunker and Von Meyer, corresponding in their fossils and mineral characters with those of the English series. So that “we can scarcely hesitate,” says Lyell, “to refer the whole to one great delta.”[78]

The overlying Weald clay crops out from beneath the Lower Greensand in various parts of Kent and Sussex, and again in the Isle of Wight, and in the Isle of Purbeck, where it reappears at the base of the chalk.

The upper division (or the Weald clay) is, as we have said, of purely fresh-water origin, and is supposed to have been the estuary of some vast river which, like the African Quorra, may have formed a delta some hundreds of miles broad, as suggested by Dr. Dunker and Von Meyer.

The Lower Greensand is known, also, as the Néocomien, after Neocomium, the Latin name of the city of Neufchatel, in Switzerland, where this formation is largely developed, and where, also, it was first recognised and established as a distinct formation. Dr. Fitton, in his excellent monograph of the Lower Cretaceous formations, gives the following descending succession of rocks as observable in many parts of Kent:—

Feet.

1. Sand, white, yellowish, or brown, with concretions of limestone and chert 70

2. Sand, with green matter 70 to 100

3. Calcareous stone, called Kentish rag 60 to 80

These divisions, which are traceable more or less from the southern part of the Isle of Wight to Hythe in Kent, present considerable variations. At Atherfield, where sixty-three distinct strata, measuring 843 feet, have been noticed, the limestone is wholly wanting, and some fossils range through the whole series, while others are confined to particular divisions; but Prof. E. Forbes states, that when the same conditions are repeated in overlying strata the same species reappear; but that changes of depth, or of the mineral nature of the sea-bottom, the presence or absence of lime or of peroxide of iron, the occurrence of a muddy, sandy, or gravelly bottom, are marked by the absence of certain species, and the predominance of others.[79]

Fig. 131.—Perna Mulleti. One-quarter natural size. a, exterior; b, part of the upper hinge.

Among the marine fauna of the Néocomian series the following are the principal. Among the Acephala, one of the largest and most abundant shells of the lower Néocomian, as displayed in the Atherfield section, is the large Perna Mulleti (Fig. 131).

The Scaphites have a singular boat-shaped form, wound with contiguous whorls in one part, which is detached at the last chamber, and projects in a more or less elongated condition.

Fig. 132.—Hamites. One-third natural size.

Hamites, Crioceras, and Ancyloceras have club-like terminations at both extremities; they may almost be considered as non-involuted Ammonites with the spiral evolutions disconnected or partially unrolled, as in the engraving (Figs. 125 and 132). Ancyloceras Matheronianus seems to have had spines projecting from the ridge of each of the convolutions.

Fig. 133.—Shell of Turritella terebra. (Living form.)

The Toxoceras had the shell also curved, and not spiral.

The Baculites had the shell differing from all Cephalopods, inasmuch as it was elongated, conical, perfectly straight, sometimes very slender, and tapering to a point.

Fig. 134.—Turrillites costatus. (Chalk.)

The Turrilites have the shell regular, spiral, and sinistral; that is, turning to the left in an oblique spiral of contiguous whorls. The engraving will convey the idea of their form (Fig. 134).

Fig. 135—Terebrirostra lyra. a, back view; b, side view.

Among others, as examples of form, we append Figs. 133, 135, 136.

Fig. 136.—Terebratula deformis.

This analysis of the marine fauna belonging to the Néocomian formation might be carried much further, did space permit, or did it promise to be useful; but, without illustration, any further merely verbal description would be almost valueless.

Numerous Reptiles, a few Birds, among which are some “Waders,” belong to the genera of Palæornis or Cimoliornis; new Molluscs in considerable quantities, and some extremely varied Zoophytes, constitute the rich fauna of the Lower Chalk. A glance at the more important of these animals, which we only know in a few mutilated fragments, is all our space allows; they are true medals of the history of our globe, medals, it is true, half effaced by time, but which consecrate the memory of departed ages.

In the year 1832 Dr. Mantell added to the wonderful discoveries he had made in the Weald of Sussex, that of the great Lizard-of-the-woods, the hylæosaurus (ὑλη, wood, σαυρος, lizard). This discovery was made in Tilgate forest, near Cuckfield, and the animal appears to have been from twenty to thirty feet in length. The osteological characters presented by the remains of the Hylæosaurus are described by Dr. Mantell as affording another example of the blending of the Crocodilian with the Lacertian type of structure; for we have, in the pectoral arch, the scapula or omoplate of a crocodile associated with the coracoid of a lizard. Another remarkable feature in these fossils is the presence of the large angular bones or spines, which, there is reason to infer, constituted a serrated crest along the middle of the back; and the numerous small oval dermal bones which appear to have been arranged in longitudinal series along each side of the dorsal fringe.

The Megalosaurus, the earliest appearance of which is among the more ancient beds of the Liassic and Oolitic series, is again found at the base of the Cretaceous rocks. It was, as we have seen, an enormous lizard, borne upon slightly raised feet; its length exceeded forty feet, and in bulk it was equal to an elephant seven feet high.

Fig. 137.—Lower Jaw of the Megalosaurus.

Fig. 138.—Tooth of Megalosaurus.

The Megalosaurus found in the ferruginous sands of Cuckfield, in Sussex, in the upper beds of the Hastings Sands, must have been at least sixty or seventy feet long. Cuvier considered that it partook both of the structure of the Iguana and the Monitors, the latter of which belong to the Lacertian Reptiles which haunt the banks of the Nile and tropical India. The Megalosaurus was probably an amphibious Saurian. The complicated structure and marvellous arrangement of the teeth prove that it was essentially carnivorous. It fed probably on other Reptiles of moderate size, such as the Crocodiles and Turtles which are found in a fossil state in the same beds. The jaw represented in Fig. 137 is the most important fragment of the animal we possess. It is the lower jaw, and supports many teeth: it shows that the head terminated in a straight muzzle, thin and flat on the sides, like that of the Gavial, the Crocodile of India. The teeth of the Megalosaurus were in perfect accord with the destructive functions with which this formidable creature was endowed. They partake at once of the nature of a knife, sabre, and saw. Vertical at their junction with the jaw, they assume, with the increased age of the animal, a backward curve, giving them the form of a gardener’s pruning-knife (Fig. 138; also c. Fig. 179). After mentioning some other particulars, respecting the teeth, Buckland says: “With teeth constructed so as to cut with the whole of their concave edge, each movement of the jaws produced the combined effect of a knife and a saw, at the same time that the point made a first incision like that made by a point of a double-cutting sword. The backward curvature taken by the teeth at their full growth renders the escape of the prey when once seized impossible. We find here, then, the same arrangements which enable mankind to put in operation many of the instruments which they employ.”

Fig. 139.—Nasal Horn of Iguanodon. Two-thirds natural size.

Fig. 140.—Ammonites rostratus. (Upper Greensand.)

The Iguanodon, signifying Iguana-toothed (from the Greek word, οδους, tooth), was more gigantic still than the Megalosaurus; one of the most colossal, indeed, of all the Saurians of the ancient world which research has yet exposed to the light of day. Professor Owen and Dr. Mantell were not agreed as to the form of the tail; the former gentleman assigning it a short tail, which would affect Dr. Mantell’s estimate of its probable length of fifty or sixty feet; the largest thigh-bone yet found measures four feet eight inches in length. The form and disposition of the feet, added to the existence of a bony horn (Fig. 139), on the upper part of the muzzle or snout, almost identifies it as a species with the existing Iguanas, the only Reptile which is known to be provided with such a horn upon the nose; there is, therefore, no doubt as to the resemblance between these two animals; but while the largest of living Iguanas scarcely exceeds a yard in length, its fossil congener was probably fifteen or sixteen times that length. It is difficult to resist the feeling of astonishment, not to say incredulity, which creeps over one while contemplating so striking a disproportion as that which subsists between this being of the ancient world and its ally of the new.

The Iguanodon carried, as we have said, a horn on its muzzle; the bone of its thigh, as we have seen, surpassed that of the Elephant in size; the form of the bone and feet demonstrates that it was formed for terrestrial locomotion; and its dental system shows that it was herbivorous.

Fig. 141.—Teeth of Iguanodon. a, young tooth; b, c, teeth further advanced, and worn. (Wealden.)

The teeth (Fig. 141), which are the most important and characteristic organs of the whole animal, are imbedded laterally in grooves, or sockets, in the dentary bone; there are three or four sockets of successional teeth on the inner side of the base of the old teeth. The place thus occupied by the edges of the teeth, their trenchant and saw-like form, their mode of curvature, the points where they become broader or narrower which turn them into a species of nippers or scissors—are all suitable for cutting and tearing the tough vegetable substances which are also found among the remains buried with this colossal reptile, a restoration of which is represented in Plate XXI., p. 296.

Fig. 142.—Fishes of the Cretaceous period. 1, Beryx Lewesiensis; 2, Osmeroides Mantelli.

The Cretaceous seas contained great numbers of Fishes, among which some were remarkable for their strange forms. The Beryx Lewesiensis (1), and the Osmeroides Mantelli (2) (Fig. 142), are restorations of these two species as they are supposed to have been in life. The Odontaspis is a new genus of Fishes which may be mentioned. Ammonites rostratus (Fig. 140), and Exogyra conica (Fig. 147), are common shells in the Upper Greensand.

XXI.—Ideal scene in the Lower Cretaceous Period, with Iguanodon and Megalosaurus.

The seas of the Lower Cretaceous period were remarkable in a zoological point of view for the great number of species and the multiplicity of generic forms of molluscous Cephalopods. The Ammonites assume quite gigantic dimensions; and we find among them new species distinguished by their furrowed transverse spaces, as in the Hamites (Fig. 132). Some of the Ancyloceras attained the magnitude of six feet, and other genera, as the Scaphites, the Toxoceras, the Crioceras (Fig. 125), and other Mollusca, unknown till this period, appeared now. Many Echinoderms, or sea-urchins, and Zoophytes, have enriched these rocks with their animal remains, and would give its seas a condition quite peculiar.

On the opposite page an ideal landscape of the period is represented (Plate XXI.), in which the Iguanodon and Megalosaurus struggle for the mastery in the centre of a forest, which enables us also to convey some idea of the vegetation of the period. Here we note a vegetation at once exotic and temperate—a flora like that of the tropics, and also resembling our own. On the left we observe a group of trees, which resemble the dicotyledonous plants of our forests. The elegant Credneria is there, whose botanical place is still doubtful, for its fruit has not been found, although it is believed to have belonged to plants with two seed-leaves, or dicotyledonous, and the arborescent Amentaceæ. An entire group of trees, composed of Ferns and Zamites, are in the background; in the extreme distance are some Palms. We also recognise in the picture the alder, the wych-elm, the maple, and the walnut-tree, or at least species analogous to these.

The Néocomian beds in France are found in Champagne, in the departments of the Aube, the Yonne, the Haute-Alps, &c. They are largely developed in Switzerland at Neufchatel, and in Germany.

1. The Lower Néocomian consists of marls and greyish clay, alternating with thin beds of grey limestone. It is very thick, and occurs at Neufchatel and in the Drôme. The fossils are Spatangus retusus, Crioceras (Fig. 125), Ammonites Asterianus, &c.

2. Orgonian (the limestone of Orgon). This group exists, also, at Aix-les-Bains in Savoy, at Grenoble, and generally in the thick, white, calcareous beds which form the precipices of the Drôme. The fossils Chama ammonia, Pigaulus, &c.

3. The Aptien (or Greensand) consists generally of marls and clay. In France it is found in the department of Vaucluse, at Apt (whence the name Aptien), in the department of the Yonne, and in the Haute-Marne. Fossils, Ancyloceras Matheronianus, Ostrea aquila, and Plicatula placunea. These beds consist here of greyish clay, which is used for making tiles; there of bluish argillaceous limestone, in black or brownish flags. In the Isle of Wight it becomes a fine sandstone, greyish and slightly argillaceous, which at Havre, and in some parts of the country of Bray, become well-developed ferruginous sandstones.

Fig. 143.—Cypris spinigera.

We have noted that the Lower Néocomian formation, although a marine deposit, is in some respects the equivalent of the Weald Clay, a fresh-water formation of considerable importance on account of its fossils. We have seen that it was either formed at the mouth of a great river, or the river was sufficiently powerful for the fresh-water current to be carried out to sea, carrying with it some animals, forming a fluviatile, or lacustrine fauna, on a small scale. These were small Crustaceans of the genus Cypris, with some molluscous Gasteropoda of the genera Melania, Paludina, and acephalous Mollusca of the five genera Cyrena, Unio, Mytilus, Cyclas, and Ostrea. Of these, Cypris spinigera (Fig. 143) and Cypris Valdensis (Fig. 144) may be considered as among the most characteristic fossils of this local fauna.

Fig. 144.—Cypris Valdensis.

The Cretaceous series is not interesting for its fossils alone; it presents also an interesting subject for study in a mineralogical point of view. The white Chalk, examined under the microscope by Ehrenberg, shows a curious globiform structure. The green part of its sandstone and limestone constitutes very singular compounds. According to the result of Berthier’s analysis, we must consider them as silicates of iron. The iron shows itself here not in beds, as in the Jurassic rocks, but in masses, in a species of pocket in the Orgonian beds. They are usually hydrates in the state of hematites, accompanied by quantities of ochre so abundant that they are frequently unworkable. In the south of France these veins were mined to a great depth by the ancient monks, who were the metallurgists of their age. But for the artist the important Orgonian beds possess a special interest; their admirable vertical fractures, their erect perpendicular peaks, each surpassing the other in boldness, form his finest studies. In the Var, the defiles of Vésubia, of the Esteron, and Tinéa, are jammed up between walls of peaks, for many hundreds of yards, between which there is scarcely room for a narrow road by the side of the roaring torrent. “In the Drôme,” says Fournet, “the entrance to the beautiful valley of the Vercors is closed during a part of the year, because, in order to enter, it is necessary to cross the two gullies, the Great and Little Goulet, through which the waters escape from the valley. Even during the dry season, he who would enter the gorge must take a foot-bath.

“This state of things could not last; and in 1848 it was curious to see miners suspended on the sides of one of these lateral precipices, some 450 feet above the torrent, and about an equal distance below the summit of the Chalk. There they began to excavate cavities or niches in the face of the rock, all placed on the same level, and successively enlarged. These were united together in such a manner as to form a road practicable for carriages; now through a gallery, now covered by a corbelling, to look over which affords a succession of surprises to the traveller.

“This is not all,” adds M. Fournet: “he who traverses the high plateaux of the country finds at every step deep diggings in the soil, designated pits or scialets, the oldest of which have their sides clothed with a curious vegetation, in which the Aucolin predominates; shelter is found in these pits from the cutting winds which rage so furiously in these elevated regions. Others form a kind of cavern, in which a temperature obtains sufficient to freeze water even in the middle of summer. These cavities form natural glaciers, which we again find upon some of the table-lands of the Jura.

“The cracks and crevasses of the limestone receive the waters produced by falling rain and melted snow; true to the laws of all fluid bodies, they filter through the rocks until they reach the lower and impervious marly beds, where they form sheets of water, which in course of time find some outlet through which they discharge themselves. In this manner subterranean galleries, sometimes of great extent, are formed, in which are assembled all the marvels which crumbling stalactites, stalagmites, placid lakes, and headlong torrents can produce; finally, these waters, forcing their way through the external orifices, give rise to those fine cascades which, with the first gushing torrent, form an actual river.”

The Albien of Alc. D’Orbigny, which Lyell considers to be the equivalent of the Gault, French authors treat as the “glauconie” formation, the name being drawn from a rock composed of chalk with greenish grains of glauconite, or silicate of iron, which is often mixed with the limestone of this formation. The fossils by which it is identified are very varied. Among its numerous types, we find Crustaceans belonging to the genera Arcania and Corystes; many new Mollusca, Buccinum, Solen, Pterodonta, Voluta, Chama, &c.; great numbers of molluscous Brachiopods, forming highly-developed submarine strata; some Echinoderms, unknown up to this period, and especially a great number of Zoophytes; some Foraminifera, and many Polyzoa (Bryozoa). The glauconitic formation consists of two groups of strata: the Gault Clay and the glauconitic chalk, or Upper Greensand and Chloritic Marl.

Upper Cretaceous Period.

During this phase of the terrestrial evolutions, the continents, to judge from the fossilised wood which we meet with in the rocks which now represent it, would be covered with a very rich vegetation, nearly identical, indeed, with that which we have described in the preceding sub-period; according to Adolphe Brongniart, the “age of angiosperms” had fairly set in; the Cretaceous flora displays, he considers, a transitional character from the Secondary to the Tertiary vegetation; that the line between the gymnosperms, or naked-seeded plants, and the angiosperms, having their seeds enclosed in seed-vessels, runs between the Upper and Lower Cretaceous formations. “We can now affirm,” says Lyell, “that these Aix-la-Chapelle plants, called Credneria, flourished before the rich reptilian fauna of the secondary rocks had ceased to exist. The Ichthyosaurus, Pterodactyle, and Mosasaurus were of coeval date with the oak, the walnut, and the fig.”[80]

The terrestrial fauna, consisting of some new Reptiles haunting the banks of rivers, and Birds of the genus Snipe, have certainly only reached us in small numbers. The remains of the marine fauna are, on the contrary, sufficiently numerous and well preserved to give us a great idea of its riches, and to enable us to assign to it a characteristic facies.

The sea of the Upper Cretaceous period bristled with numerous submarine reefs, occupying a vast extent of its bed—reefs formed of Rudistes (Lamarck), and of immense quantities of various kinds of corals which are everywhere associated with them. The Polyps, in short, attain here one of the principal epochs of their existence, and present a remarkable development of forms; the same occurs with the Polyzoa (Bryozoa) and Amorphozoa; while, on the contrary, the reign of the Cephalopods seems to end. Beautiful types of these ancient reefs have been revealed to us, and we discover that they have been formed under the influence of submarine currents, which accumulated masses of these animals at certain points. Nothing is more curious than this assemblage of Rudistes—still standing erect, isolated or in groups—as may be seen, for instance, at the summit of the mountains of the Cornes in the Corbières, upon the banks of the pond of Berre in Provence, and in the environs of Martigues, at La Cadière, at Figuières, and particularly above Beausset, near Toulon.

“It seems,” says Alcide D’Orbigny, “as if the sea had retired in order to show us, still intact, the submarine fauna of this period, such as it was when in life. There are here enormous groups of Hippurites in their places, surrounded by Polyps, Echinoderms, and Molluscs, which lived in union in these animal colonies, analogous to those which still exist in the coral-reefs of the Antilles and Oceania. In order that these groups should have been preserved intact, they must first have been covered suddenly by sediment, which, being removed by the action of the atmosphere, reveals to us, in their most secret details, this Nature of the past.”

In the Jurassic period we have already met with these isles or reefs formed by the accumulation of Coral and other Zoophytes; they even constituted, at that period, an entire formation called the Coral-rag. The same phenomenon, reproduced in the Cretaceous seas, gave rise to similar calcareous formations. We need not repeat what we have said already on this subject when describing the Jurassic period. The coral or madrepore isles of the Jurassic epoch and the reefs of Rudistes and Hippurites of the Cretaceous period have the same origin, and the atolls of Oceania are reproductions in our own day of precisely similar phenomena.

The invertebrate animals which characterise the Cretaceous age are among

Cephalopoda.

Nautilus sublævigatus and N. Danicus; Ammonites rostratus; Belemnitella mucronata.

Gasteropoda.

Voluta elongata; Phorus canaliculatus; Nerinea bisulcata; Pleurotomaria Fleuriausa, and P. Santonensis; Natica supracretacea.

Acephala.

Trigonia scabra; Inoceramus problematicus and I. Lamarckii; Clavigella cretacea; Pholadomya æquivalvis; Spondylus spinosus; Ostrea vesicularis; Ostrea larva; Janira quadricostata; Arca Gravesii; Hippurites Toucasianus and H. organisans; Caprina Aguilloni; Radiolites radiosus, and R. acuticostus.

Brachiopoda.

Crania Ignabergensis; Terebratula obesa.

Polyzoa (Bryozoa) and Eschinodemata.

Reticulipora obliqua; Ananchytes ovatus; Micraster cor-anguinum, Hemiaster bucardium and H. Fourneli; Galerites albogalerus; Cidaris Forchammeri; Palæocoma Furstembergii.

1. Polypi; 2. Foraminifera; 3. Amorphozoa.

1. Cycollites elliptica; Thecosmilia rudis; Enallocœnia ramosa; Meandrina Pyrenaica; Synhelia Sharpeana. 2. Orbitoides media; Lituola nautiloidea; Flabellina rugosa. 3. Coscinopora cupuliformis; Camerospongia fungiformis.

Among the numerous beings which inhabited the Upper Cretaceous seas there is one which, by its organisation, its proportions, and the despotic empire which it would exercise in the bosom of the waters, is certainly most worthy of our attention. We speak of the Mosasaurus, which was long known as the great animal of Maestricht, because its remains were found near that city in the most modern of the Cretaceous deposits.

In 1780 a discovery was made in the quarries of Saint Peter’s Rocks, near Maestricht, of the head of a great Saurian, which may now be seen in the Museum of Natural History in Paris. This discovery baffled all the science of the naturalists, at a period when the knowledge of these ancient beings was still in its infancy. One saw in it the head of a Crocodile; another, that of a Whale; memoirs and monographs rained down, without throwing much light on the subject. It required all the efforts of Adrian Camper, joined to those of the immortal Cuvier, to assign its true zoological place to the Maestricht animal. The controversy over this fine fossil engaged the attention of the learned for the remainder of the last century and far into the present.

Maestricht is a city of the Netherlands, built on the banks of the Meuse. At the gates of this city, in the hills which skirt the left or western bank of the river, there rises a solid mass of cretaceous formation known as Saint Peter’s Rocks. In composition these beds correspond with the Meudon chalk beds, and they contain similar fossils. The quarries are about 100 feet deep, consisting in the upper part of twenty feet abounding in corals and Polyzoa, succeeded by fifty feet of soft yellowish limestone, furnishing a fine building stone, which has been quarried from time immemorial, and extends up to the environs of Liège; this is succeeded by a few inches of greenish soil with Encrinites, and then by a very white chalk with layers of flints. The quarry is filled with marine fossils, often of great size.

These fossil remains, naturally enough, attracted the attention of the curious, and led many to visit the quarries; but of all the discoveries which attracted attention the greatest interest attached to the gigantic animal under consideration. Among those interested by the discovery of these strange vestiges was an officer of the garrison of Maestricht, named Drouin. He purchased the bones of the workmen as the pick disengaged them from the rock, and concluded by forming a collection in Maestricht, which was spoken of with admiration. In 1766, the trustees of the British Museum, hearing of this curiosity, purchased it, and had it removed to London. Incited by the example of Drouin, Hoffmann, the surgeon of the garrison, set about forming a similar collection, and his collection soon exceeded that of Drouin’s Museum in riches. It was in 1780 that he purchased of the quarrymen the magnificent fossil head, exceeding six feet in length, which has since so exercised the sagacity of naturalists.

Hoffman did not long enjoy the fruits of his precious prize, however; the chapter of the church of Maestricht claimed, with more or less foundation, certain rights of property; and in spite of all protest, the head of the Crocodile of Maestricht, as it was already called, passed into the hands of the Dean of the Chapter, named Goddin, who enjoyed the possession of his antediluvian trophy until an unforeseen incident changed the aspect of things. This incident was nothing less than the bombardment and surrender of Maestricht to the Army of the North under Kleber, in 1794.

The Army of the North did not enter upon a campaign to obtain the crania of Crocodiles, but it had on its staff a savant who was devoted to such pacific conquests. Faujas de Saint-Fond, who was the predecessor of Cordier in the Zoological Chair of the Jardin des Plantes, was attached to the Army of the North as Scientific Commissioner; and it is suspected that, in soliciting this mission, our naturalist had in his eye the already famous head of the Crocodile of the Meuse. However that may be, Maestricht fell into the hands of the French, and Faujas eagerly claimed the famous fossil for the French nation, which was packed with the care due to a relic numbering so many thousands of ages, and dispatched to the Museum of Natural History in Paris. On its arrival, Faujas undertook a labour which, as he thought, was to cover him with glory. He commenced the publication of a work entitled “The Mountain of Saint Peter of Maestricht,” describing all the fossil objects found in the Dutch quarry there, especially the Great Animal of Maestricht. He endeavoured to prove that this animal was a Crocodile.

Unfortunately for the glory of Faujas, a Dutch savant had devoted himself to the same study. Adrian Camper was the son of a great anatomist of Leyden, Pierre Camper, who had purchased of the heirs of the surgeon Hoffman some parts of the skeleton of the animal found in the quarry of Saint Peter. He had even published in the Philosophical Transactions of London, as early as 1786, a memoir, in which the animal is classed as a Whale. At the death of his father, Adrian Camper re-examined the skeleton, and in a work which Cuvier quotes with admiration, he fixed the ideas which were until then floating about. He proved that the bones belonged neither to a Fish, nor a Whale, nor to a Crocodile, but rather to a particular genus of Saurian Reptiles, or marine lizards, closely resembling in many important structural characters, existing Monitors and Iguanas, and peculiar to rocks of the Cretaceous period, both in Europe and America. Long before Faujas had finished the publication of his work on La Montagne de Saint-Pierre that of Adrian Camper had appeared, and totally changed the ideas of the world on this subject. It did not, however, hinder Faujas from continuing to call his animal the Crocodile of Maestricht. He even announced, some time after, that Adrian Camper was also of his opinion. “Nevertheless,” says Cuvier, “it is as far from the Crocodile as it is from the Iguana; and these two animals differ as much from each other in their teeth, bones, and viscera, as the ape differs from the cat, or the elephant from the horse.”

Fig. 145. a, skull of Monitor Niloticus; b, under-jaw of same.

The masterly memoir of Cuvier, while confirming all the views of Camper, has restored the individuality of this surprising being, which has since received the name of Mosasaurus, that is to say, Saurian or Lizard of the Meuse. It appears, from the researches of Camper and Cuvier, that this reptile of the ancient world formed an intermediate genus between the group of the Lacertilia, which comprehends the Monitors (represented in Fig. 145), and the ordinary Lizards; and the Lacertilia, whose palates are armed with teeth, a group which embraces the Iguana and the Anolis. In respect to the Crocodiles, the Mosasaurus resembles them in so far as they all belong to the same class of Reptiles.

The idea of a lizard, adapted for living and moving with rapidity at the bottom of the water, is not readily conceived; but a careful study of the skeleton of the Mosasaurus reveals to us the secret of this anatomical mechanism. The vertebræ of the animal are concave in front and convex behind; they are attached by means of orbicular or arched articulations, which permitted it to execute easily movements of flexion in any direction. From the middle of the back to the extremity of the tail these vertebræ are deficient in the articular processes which support and strengthen the trunk of terrestrial vertebrated animals: they resemble in this respect the vertebræ of the Dolphins; an organisation necessary to render swimming easy. The tail, compressed laterally at the same time that it was thick in a vertical direction, constituted a straight rudder, short, solid, and of great power. An arched bone was firmly attached to the body of each caudal vertebra in the same manner as in Fishes, for the purpose of giving increased power to the tail; finally, the extremities of the animal could scarcely be called feet, but rather paddles, like those of the Ichthyosaurus, the Plesiosaurus, and the Whale. We see in Fig. 146 that the jaws are armed with numerous teeth, fixed in their sockets by an osseous base, both large and solid. Moreover, an altogether peculiar dental system occupies the vault of the palate, as in the case of certain Serpents and Fishes, where the teeth are directed backwards, like the barb of a hook, thus opposing themselves to the escape of prey. Such a disposition of the teeth sufficiently proves the destructive character of this Saurian.