XIX.—Fig. 1.—Apiocrinites rotundus.

Fig. 2.—Encrinus liliiformis.

Upper extremity of the pear-shaped head; 4, a vertical section showing the enlargement of the ahmentary 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. roiimdus 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 v/ay 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 RocJz^ 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 Vachcs 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 60a 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 Grypha^a 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 unhke those now existing in the|rPacific 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 Inferieure. In the Alps the Diccras limestone is regarded, by most geologists, as coeval with the English Coral Rag.

265

UPPER OOLITE,

Upper Oolite.

Some marsupial Mammals have left their remains in the Upper Oolite as in the Lower. They belong, to the genus Sphalacotheriuin,

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

Besides the Plesiosauri and Teleosauri, there still lived in the maritime regions a Crocodile, the Macrorhynchus; and the monstrous Pceciloplenron^ with sharp cutting teeth, one of the most formidable animals of this epoch; the HylccosaurKs, Cetiosaunis, Staiosatirus^ and Streptospo?idylus^ and among the Turtles, the Eiiiys and Flatauys.

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.

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. The Oolitic seas of this series contained Fishes belonging to the genera Asteracaiithus, 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 i^\y[ Zoophytes in the fossil state testify to the

Fig. 123. existence of these extraordinary animals.

Shell of Physafoniinaiis. ^j^^ f^^g-jg characteristic of the fauna of the period include Ammonites decipiens and A. giganteus^ Natica elegans and hemispherica, Ostrea deltoidea and O, 7)irgiila^ Trigonia gibbosciy Pholadomya multicostaia and P. acuticostata, Terebratula subsella, and Hemicidaris Furbeckensis. Some Fishes, Turtles, Fahidina, Fliysa (Fig. 123), Unio, Flanorbis (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, Cycadeaceae, and Conifers; in the ponds and swamps some Zosterse. The ZostercB are monocotyledonous plants of the family of the Naidaceae, 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.

On the opposite page an ideal landscape of the period (Plate XX.) represents some of the features of the Upper Oolite, especially the

w^iii

\L^ 1;*

vegetation of the Jurassic period. The Sphaiophyllum^ among the Tree-ferns, is predominant in this vegetation; some Pandaiias, a few Zamites, and many Comfers, but we perceive no Palms. A coral islet rises out of the sea, having somewhat of the form of the atoiis of Oceania, indicating the importance these fonnations assumed in the Jurassic period. The animals represented are the Crocodileimus of Jourdan, the Rainphorymchus^ with the imprints which characterise its footsteps, and some of the invertebrated animals of the period, as the Asferia, Coinaticla^ Heinicidaris, Pteroceras. Aloft in the air floats the bird of Solenhofen, the Archccopteryx^ 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: i. The Piirbeck Beds; 2. The Portlarid 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, Cardiiun. siriatiilum and Osirea deltoidca^ are found throughout England: in France, at TonneiTe, Dept. Yonne; at Havre; at Honfleur; at Mauvage; in the department of the Meuse it is so rich in shells of Ostrea delioidea and O. vii-gnla, that, " near Clermont in Argonne, a few leagues from St. Menehould," says Lyell,'-' "where these indurated marls crop out from beneath the Gault, I have seen them {Gryphea virion /a) 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 quanied 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-Chateau, Auxenre, and Gray (Haute Saone).

"Elements of Geology," p. 393.

The Isle, or rather peninsula of Portland,'"' off the Dorsetshire coast, rises considerably above the sea-level, presenting on the side of the port a bold Hne of cliffs, connected with the mainland by the Chesil bank,t 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 tiie 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

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