The World Before the Deluge Part 23

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]

[79] Ibid, p. 340.

Among the marine fauna of the Neocomian series the following are the princ.i.p.al. Among the _Acephala_, one of the largest and most abundant sh.e.l.ls of the lower Neocomian, as displayed in the Atherfield section, is the large _Perna Mulleti_ (Fig. 131).

[Ill.u.s.tration: Fig. 131.--Perna Mulleti. One-quarter natural size.

_a_, exterior; _b_, part of the upper hinge.]

[Ill.u.s.tration: Fig. 132.--Hamites. One-third natural size.]

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.

_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 Matheronia.n.u.s_ seems to have had spines projecting from the ridge of each of the convolutions.

[Ill.u.s.tration: Fig. 133.--Sh.e.l.l of Turritella terebra.

(Living form.)]

[Ill.u.s.tration: Fig. 134.--Turrillites costatus.

(Chalk.)]

The _Toxoceras_ had the sh.e.l.l also curved, and not spiral.

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

The _Turrilites_ have the sh.e.l.l 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).

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

This a.n.a.lysis of the marine fauna belonging to the Neocomian formation might be carried much further, did s.p.a.ce permit, or did it promise to be useful; but, without ill.u.s.tration, any further merely verbal description would be almost valueless.

[Ill.u.s.tration: Fig. 135--Terebrirostra lyra.

_a_, back view; _b_, side view.]

[Ill.u.s.tration: Fig. 136.--Terebratula deformis.]

Numerous Reptiles, a few Birds, among which are some "Waders," belong to the genera of _Palaeornis_ or _Cimoliornis_; new Molluscs in considerable quant.i.ties, and some extremely varied Zoophytes, const.i.tute 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 s.p.a.ce 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 Suss.e.x, that of the great Lizard-of-the-woods, the _hylaeosaurus_ (???, _wood_, sa????, _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 Hylaeosaurus 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 a.s.sociated 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, const.i.tuted 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 Lia.s.sic 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.

[Ill.u.s.tration: Fig. 137.--Lower Jaw of the Megalosaurus.]

[Ill.u.s.tration: Fig. 138.--Tooth of Megalosaurus.]

The Megalosaurus found in the ferruginous sands of Cuckfield, in Suss.e.x, 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 a.s.sume, 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."

[Ill.u.s.tration: Fig. 139.--Nasal Horn of Iguanodon.

Two-thirds natural size.]

[Ill.u.s.tration: Fig. 140.--Ammonites rostratus.

(Upper Greensand.)]

The _Iguanodon_, signifying _Iguana-toothed_ (from the Greek word, ?d???, _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 a.s.signing 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.

[Ill.u.s.tration: Fig. 141.--Teeth of Iguanodon.

_a_, young tooth; _b_, _c_, teeth further advanced, and worn.

(Wealden.)]

The Iguanodon carried, as we have said, a horn on its muzzle; the bone of its thigh, as we have seen, surpa.s.sed 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.

[Ill.u.s.tration: Fig. 142.--Fishes of the Cretaceous period.

1, Beryx Lewesiensis; 2, Osmeroides Mantelli.]

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.

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 sh.e.l.ls in the Upper Greensand.

[Ill.u.s.tration: 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 a.s.sume quite gigantic dimensions; and we find among them new species distinguished by their furrowed transverse s.p.a.ces, 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 Amentaceae. 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 a.n.a.logous to these.

The Neocomian 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 Neocomian consists of marls and greyish clay, alternating with thin beds of grey limestone. It is very thick, and occurs at Neufchatel and in the Drome. The fossils are _Spatangus retusus_, _Crioceras_ (Fig. 125), _Ammonites Asteria.n.u.s_, &c.

2. _Orgonian_ (the limestone of Orgon). This group exists, also, at Aix-les-Bains in Savoy, at Gren.o.ble, and generally in the thick, white, calcareous beds which form the precipices of the Drome. The fossils _Chama ammonia_, _Pigaulus_, &c.