lection; and on the top of the Case a splendid specimen from Sussex, consisting of the anterior part of an enormous fish. The largest fragments of some of the Wealden Lepidoti indicate the total length of the fish to have been twelve or

LIGN. 87.-SCALES AND FIN-RAY OF LEPIDOTUS MANTELLI. TILGATE FOREST.

Fig. 1.-Scale, with a single process of attachment.

2. One of the scales of the dorsal line.

3.-Scale (external surface), with a bifurcating process of attachment. 4.-Scale (viewed on the inner surface), showing the lateral processes. 5. The front RAY of the dorsal fin, covered with two rows of enamelled scales, and two other rays behind it.

(nat. size.)

fourteen feet; and the width of the body from three to four feet.

These fishes resembled the Carps in their general outline but have no anatomical relations to that family. The jaws are short and rounded, and furnished with rows of obtuse hemispherical teeth; the head, and even face, were encased with osseous enamelled plates, which are often found separately imbedded in the rock; there are several large examples in the collection. The dorsal and pectoral fins are very strong, and consist of several bony rays. There is a double row of acuminated, enamelled scales, arranged ob

ray

of

liquely, on the anterior margin of the dorsal and anal fins, and on both margins of the caudal. (Part of the first a dorsal fin, with scales, is represented Lign. 87.)

Lepidotus minor.-The smaller species is often found in the Purbeck limestone almost as entire as if recent, of which the beautiful Ichthyolite in Case B (No. 6), is an example.

At the bottom of this Case there is a specimen of Lepidotus semiserratus from the Lias of Whitby, remarkable for the per

fect state of the head, which is uncompressed, and exhibits its normal form.

The habits of the Lepidoti, as indicated by the form and structure of the teeth, were those of fishes whose food consisted of crustaceans, shelly mollusca, &c.; for the dental organs are peculiarly adapted for the crushing and grinding of such substances; and the teeth of the adult fishes are generally worn down by use.

Pholidophorus.-This is a genus of small fishes allied to the Lepidotus, some species of which abound in the Lias and Oolite; their remains are commonly found associated with the skeletons of the enalosaurians, at Lyme Regis, Barrow-onSoar, &c.; they have only brush-teeth. There are many specimens in this Case from Solenhofen.

SAUROIDS.-Wall-case B. (Nos. 7, 8, 9, 10.)-The fishes of the SAUROID (lizard-like) family were thus named by M. Agassiz, in consequence of certain peculiarities of organization which are found in no other animals of their class, but exist in reptiles.1

1 "Recherches sur les Poissons Fossiles," par L. Agassiz, tome ii.

There are but two living genera, namely, the Lepidosteus, of which several species inhabit the rivers of America; and the Polypterus, that comprises two species, one inhabiting the Nile, and the other the rivers of Senegal. In these fishes the bones of the skull are closely connected by sutures; the teeth are large, conical, and longitudinally striated, as in the crocodile; the spinous processes are united to the bodies of the vertebræ by suture, as in most reptiles; and the ribs are articulated to the extremities of the transverse processes; the skeleton is osseous; the scales are flat, rhomboidal, and parallel to the body. Even in the soft parts many analogies are presented; thus the Lepidosteus has a glottis, as in the Siren, and a cellular air-bladder, with a tracheal vessel, resembling the lungs of an Ophidian (serpent). These fishes are the only living representatives of those voracious tribes of the ancient marine faunas, whose remains abound in the secondary formations.

The fossil remains of the fishes of this family have often been mistaken for those of reptiles, particularly the teeth, which from their large size, conical figure, enamelled and striated surface, and internal cavity, were supposed to belong to crocodiles. These teeth consist of two kinds: the outer, or fish-like system, consisting of numerous small brush-teeth; and an inner row of large, pointed, conical, striated, enamelled teeth, placed at a distance from each other, as seen in the fine jaws of Rhizodus in No. 9, of Case B, (p. 433.)2

The sauroids, like the lepidoids, form two groups: 1, the homercercals contain fourteen or fifteen genera, among which are the Leptolepis, Aspidorhynchus, and Belonostomus; 2, the heterocercal tribe, which includes ten or twelve genera, and among them some of the largest and most remarkable ichthyolites of the Carboniferous system, viz. the Rhizodus, Megalichthys, and Saurichthys.

Leptolepis.-Wall-case B. (No. 7.)-The small fossil fishes, resembling a fry of Herrings, in the white lias of Solen

An interesting paper, "On the Microscopic Structure of the Teeth of the Lepidostei, and their analogy with those of the Labyrinthodonts, with a Plate," by Dr. Jeffries Wyman, will be found in "Amer. Journ. of Science," October, 1843, p. 359.

2 See "Medals of Creation," p. 651.

hofen, on the uppermost ledge, and from the Oxford Clay of Chippenham, immediately beneath, belong to this sauroid genus, which comprises sixteen or eighteen species, that are abundant in the upper divisions of the Oolite. The species from Chippenham is the L. macropthalmus; that from Solenhofen, L. Knorrii.

Cololites. On the front of the same shelf are placed some small slabs of Solenhofen limestone, on which are convoluted worm-like bodies, formerly termed lumbricarites, from the supposition that they were petrified earth-worms. These curious fossils M. Agassiz has ascertained to be the intestines of fishes, and has, therefore, named them "Cololites."

Aspidorhynchus.-Wall-case B. (No. 10.)-In the lithographic stone of Solenhofen, specimens of sauroid fishes, closely related to Lepidotus, are discovered; they differ from the latter genus in the extreme shortness of the lower jaw, and the prolongation of the upper one into a long beak, bearing teeth even in that part which projects beyond the lower maxilla. The scales on the sides of the body are very high, and the tail is homocercal. There is a fine specimen (Asp. acutirostris) from Solenhofen in this Case, twenty-two inches in length. Near this specimen there is an ichthyolite of the same genus (Asp. Comptoni) from South America.

BELONOSTOMUS (B. cinctus).— Wall-case B. (No. 10.)—In 1820, I discovered the ichthyolites thus labelled, in the chalk, at Lewes; the great extent of the scales on the side of the body, in a vertical direction, was so remarkable, that until portions of the jaws, with teeth and other parts of the body, were obtained, the affinities of the original could not be determined. This fish, M. Agassiz estimated at three feet in length. A fragment, six inches long, of this species, is figured in Mr. Dixon's work, Pl. XXXV. fig. 3. I have recently discovered remains of this genus in the Wealden of the Isle of Wight, associated with teeth and scales of Lepidoti.

Pygopterus (P. Humboldtii).-Wall-case B. (No. 10,)-In this Case there is an ichthyolite from the copper-slate of

1 Figured in Dr. Buckland's "Bridgewater Essay," Pl. XV. See also "Medals of Creation," p. 657..

Mansfield, belonging to this genus of heterocercal sauroids, which is remarkably fine. It is a large species, with small scales, and the pectoral fin has a strong spine, or ray. Of Acrolepis, a nearly related genus, there is an example from the same locality at the bottom of this Case.1

A fine ichthyolite of the heterocercal sauroid genus, Platygnathus, from Dura Den, is placed immediately above the last

mentioned fossil.

Megalichthys; Rhizodus; Saurichthys.-Wall-case B. (No. 9.) The specimens thus labelled are remains of three genera of heterocercal sauroid fishes, from the carboniferous deposits of Scotland, remarkable for the form and enormous size of their teeth and jaws, and the strong enamelled plates of the cranium. The conical, striated, gigantic teeth, some of which are five or six inches in length, so closely resemble those of crocodilian saurians, that they were generally ascribed to reptiles, till M. Agassiz pointed out the true characters of the originals. In Saurichthys the crown of the tooth is separated from the fang by a constriction, and the teeth are implanted in a furrow, or groove, as in the Ichthyosaurus. Remains of several species are found in the Muschelkalk.

The Megalichthys, a genus first made known by the elegant Memoir on the carboniferous deposits of Burdie House, near Edinburgh, by Dr. Hibbert, in 1834, has enormous conical,

2 In the "Trans. Royal Soc. Edinburgh," vol. xiii.