Coprolites of Macropoma. (No. 13.)-There is a large number of coprolites in this Case, which in all probability are referable to these fishes. They show that the spiral convolutions were fewer in the intestines of the Macropoma than in the Sharks.'

Lophiostomus Dixoni.-The chalk ichthyolite thus named (by Sir Philip Egerton) is from a quarry near Alfriston, in Sussex, and was collected by Captain Beckford, R.N. of Ryde, in whose choice cabinet of fossils I detected it as an unknown ganoid fish, and induced the liberal owner to add it to the National Collection. It will be figured and described in the "Memoirs of the Museum of Practical Geology." It is allied to the Macropoma, but differs in many essential characters: the large mouth garnished with numerous very small, slender, conical, fluted teeth, its granulated cranial plates, the form and structure of the lower jaw, the branchial plates, and the scales, which Professor Williamson informs me are altogether peculiar, render it a valuable addition to the Ichthyolites of the British Museum. The specific name was proposed by me, to commemorate the late F. Dixon, Esq. of Worthing.

SCLERODERMS.-This family of ganoids, to which the Diodons and Ostracions belong, besides certain peculiar modifications of the jaws, is distinguished by the dermal integuments, which consist of polygonal or rhomboidal plates, spread over the body like a tesselated cuirass; the skeleton is fibrous; the recent types are exclusively the inhabitants of the seas of hot climates.

Dercetis elongatus.- Wall-case C. (No. 15, 16, Middle shelves.)-This is a very remarkable fossil fish from the chalk, near Lewes, which I discovered in 1818. The specimens commonly met with consist of fragments of the long subcylindrical body, covered with small scales, from a few inches to two feet in length, without any traces of the dermal scutcheons, fins, tail, or head; as in many examples in this Case, all of which are from my collection. The Dercetis had on each side of the body three rows of dermal scutcheons, like those of the Sturgeons; the intervals between them were

1 See "Medals of Creation," p. 650.

2" Muræna? Lewesiensis." "Fossils of the South Downs," tab. xxxiv. fig. 10, 11. See " Medals of Creation," p. 658.

covered with small scales. The cranium and elongated jaws, with teeth, are seen in an unique specimen in this Case; it is figured in "The Wonders of Geology," p. 349.

Blochius longirostris.-There is a fine example of this Monte Bolca ichthyolite, nineteen inches long, placed near the specimens of Dercetis. This genus resembles Belonostomus in its slender muzzle and general form; but it has brushteeth and scutcheon-like scales, as in the Dercetis; the cranium with the beak measures nine inches in length.

GYMNODONS; SILUROIDS.-Wall-case C. (No. 15, 16.)—Of the former family, which closely resembles the Diodons, three species are found in the strata of Monte Bolca, of which there are specimens in the collection. The Siluroids are related to the Silurus, and a specimen from Bracklesham, formerly in Mr. Dixon's collection, is placed in this Case.

PYCNODONS. -Wall-case C. (No. 15, 16, Lower shelves.)— In this family of fishes the jaws are paved with rows of rounded, or elongated teeth; and many of the fossil species are only known by these organs. There are many beautiful fossils of this kind in the Case before us. I can only direct attention to several jaws, and many teeth of the genus Pycnodus, from the Wealden and Oolite; and to one extraordinarily perfect lower jaw of an allied genus Gyrodus, on the middle Shelf: it is labelled "from Poulshot, near Devizes :” every tooth is as perfect as when recent.

We now proceed to the examination of the Ichthyolites of the next order; the Ctenoids, occupying the compartments of Nos. 17 to 20 inclusive, in Wall-case C; the Cycloids, Cases C and D, and the Placoids, in the Table-cases Nos. 2, 4, 6, 8, 10, and 12 (see ante, p. 410), will also be included in the same division of the present Chapter.

1 See " Medals of Creation," p. 650.

CHAPTER V.

PART III.

FOSSIL FISHES OF THE CTENOID, CYCLOID, AND
PLACOID ORDERS.

CTENOID ORDER-PERCA-BERYX-SMERDIS-MONTE BOLCA ICHTHYOLITES. CYCLOID ORDER;-ENCHODUS-SAURODON-HYPSODON-CYPRINOIDS — ESOCIDS -HALICOIDS-OSMEROIDS-ACROGNATHUS-AULOLEPIS

MALLOTUS.

PLACOID ORDER;-CHIMEROIDS-SQUALIDE-HY BODONS-CESTRACIONS——— PRISTIDES-RAYS-ICHTHYODORULITES-GEOLOGICAL DISTRIBUTION OF FOS

SIL FISHES-GENERA OF ICHTHYOLITES IN THE BRITISH MUSEUM.

CTENOID ORDER.-The fishes of this Order, of which the Perch is the type, have imbricated laminated scales, the posterior margins of which are round and finely pectinated; i. e. divided into small teeth like a comb.

The Ctenoidians first appear in the cretaceous formation, those from the slate of Glaris being the most ancient known; certain species and genera are abundant in the White Chalk of the south-east of England, and of Germany; and may have been collected from strata of the same age in the Brazils. In the tertiary limestones of Monte Bolca there are numerous Ctenoid Ichthyolites.

Almost all the fishes of this order in the Cretaceous formation are of extinct genera. One half of those from the eocene of Monte Bolca are also of lost generic types; whilst all the Ctenoids of the newer tertiary deposits belong to existing genera. The fossil Ctenoids in the British Museum comprise nearly thirty genera, belonging to eight families; a list of the whole is subjoined. I proceed to point out a few of the most interesting specimens.

PERCA.― Wall-case C. (No. 17.)-Of this typical genus of the Ctenoid order, there is a beautiful example of Perca lepidota, from the lacustrine deposits of Eningen (ante, p. 184).1

These tables show the position of the principal Ichthyolites in Case C. No. 17, 18.

BERYX.-Wall-case C. (No. 17, 18.)-This fine series of Ichthyolites from the Chalk of Sussex, (formerly in my collection,) contains four species of a genus of the Perch family, named Beryx, of which there are two existing species in the Australian seas. The first that I succeeded in clearing from the chalk of Lewes, was the specimen of Beryx figured in my "Fossils of the South Downs," tab. 34, and which is in the Case before us; it was the first published representation of an Ichthyolite from the cretaceous formation of England; the fossil remains of fishes previously collected and described by authors, consisted of the teeth, bones, &c., but no one appears to have suspected that the scaly covering, with the fins, branchial arches, cranial bones, jaws, and teeth, were preserved, and could be displayed in their original position, by the skilful removal of the surrounding stone.

LIGN 90. BERYX LEWESIENSIS, FROM THE CHALK, LEWES.
(nat. size.)

The fishes of the genus Beryx are closely allied to the common Perches; they have one dorsal fin with several spinous rays in front of the soft rays, and the head is very large: the jaws are covered with a broad band of brush-teeth. The orbit is large, and often contains the capsule of the eye; the scales are relatively very large, the vertebræ large and short, with long apophyses, and the ribs short. The Beryx Lewesiensis, (Lign. 90,) is the most common of the Icthyolites of the white chalk; it is called the "Johnny-Dory" by the quarrymen of Sussex. Another and larger species (B. superbus), sometimes thirteen inches long, with very large and broad scales, occurs in the lower chalk at Lewes. There are two species from the chalk-marl;-B. radians, the scales of which are fringed with minute diverging spines; and B. microcephalus, distinguished by its elongated form and small head. There are examples of both in the collection, from near Lewes,2

See "Medals of Creation," p. 561, and "Wonders of Geology," pp. 350, 351.

2 Of this rare Ichthyolite, I have lately been presented with a fine specimen from Clayton, Sussex, by my friend, Frederick Harford, Esq.

SMERDIS. (S. minutus.)-Wall-case C.-Certain strata of the eocene formation near Aix in Provence, abound in fossil shells, plants, insects, and fishes. The elegant little fish named Smerdis, a genus belonging to the tribe of Percoids, with two dorsal fins, and seven branchiostegous

(nat.size.)

rays, occurs in shoals, often grouped together in great numbers in the same slab of laminated limestone, and in every variety of position. There are numerous specimens in this Case, which were formerly in my collection.' The Smerdis minutus is from one to three inches long, and about the dimensions of a perch a year old. MONTE BOLCA ICHTHYOLITES. Wall-case C. The Ichthyolites of Monte Bolca must be familiar to the reader, for in consequence of the abundance and beauty of these fossils, specimens are to be seen in almost every cabinet of organic remains. They are found in a tertiary cream-coloured fissile limestone, that generally splits in the direction in which the fishes are imbedded; hence the perfect animal, from the muzzle to the tail, with its fins expanded, is often obtained.2 Referring to "The Wonders of Geology," p. 265, for an account of these deposits, I can only state, in brief, that there are in the collection under exami

1 The Chalk Ichthyolites in the British Museum, amounting to several hundred specimens, were, with but few exceptions, collected by me. The beautiful state of these fossils when in my possession, called forth the following remarks from M. Agassiz:

"Tout le monde sait que le Musée de M. Mantell à Brighton, est une collection classique pour la Craie et la formation Veldienne. Les soins minutieux que M. Mantell a donnés depuis bien des années à ces fossiles, les ont rendus plus parfaits que tous ceux des autres musées; car souvent il est parvenu à les detacher entièrement de la roche dans laquelle ils se trouvaient, ou du moins à les produire en relief, en détachant toutes les matières solides qui recouvraient les parties les mieux conservées de l'animal."-Recherches sur les Poissons Fossiles, par M. Louis Agassiz. 2 See "Wonders of Geology," p. 260.