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striated, hollow teeth, very closely resembling those of saurians; the head is encased in thick osseous plates, as in the recent Polypterus; the body is covered by large granulated scales. There are a fine lower jaw, teeth, and scales of M. Hibberti in this Case.


Rhizodus. This fish, though clearly distinct from the Megalichthys, is often confounded with it by collectors. The genus was established from some detached teeth and jaws; the scales are thinner, larger, and smoother than in Megalichthys, and their enamelled surface is finely punctated. The great strength of the cephalic plates, and of the jaws and teeth, of this powerful carnivorous fish, are well shown in the fossil remains from Burdie House, and Carluke, in Perthshire, which lie on the middle shelf of this compartment of Case B.

The conditions under which the remains of these enormous fishes are found imbedded at Burdie House, are highly interesting, for the limestone and marls in which they occur are at the bottom of the Coal formation, and abound in the foliage of ferns and other terrestrial plants, freshwater shells and crustaceans, and coprolites. These deposits must, therefore, have been formed in a lake, or estuary, frequented by predaceous sauroids; in like manner, as we have already shown, the bays and streams of the Country of the Iguanodon swarmed with the lepidoid fishes of the Wealden epoch.

Before proceeding to the next family of Ganoids, I would direct the palæontologist to the specimens of Eugnathus (E. speciosus), Wall-case B (9), and Ptycholepis (P. Bollensis), from the Lias of Wirtemberg; two genera of voracious sauroids, which are characterised by their unequal-lobed tail, large fins, and furrowed scales. Eleven species of Eugnathus have been discovered in the lias at Lyme Regis; only one species of Ptycholepis is known.

CELACANTHS (hollow spine).—This family of Ganoids is distinguished from the rest of the order by the tubular or hollow structure of the fin-rays and spinous processes; the prolonga


'See Dr. Buckland's "Bridgewater Essay," Pl. XXVII.

2 Mr. Miller observes, "they were cartilaginous within, and covered externally by a thin osseous crust or shell, which alone survives.""The Asterolepis," p. 37.


tion of the vertebral column between the principal lobes of the tail, and the articulation of the caudal rays by interapophyses. The fishes of this family are abundant in the Carboniferous and Devonian formations, and there are a few genera in the Triassic, Oolitic, and Cretaceous deposits: but no ichthyolites of this family have been observed in strata above the chalk. There are many splendid specimens of the principal types in Case B (Nos. 14, 15); especially of the Holoptychius from Scotland, and the Macropoma of the Chalk, from Lewes in Sussex.

HOLOPTYCHIUS.-Wall-case B. (No. 14.)—In this genus, the scales, which are very large, are deeply corrugated, and the bones of the head sculptured and granulated; the teeth are large, conical, and of great density; the ventral fins are nearer the tail than in the other ganoids; some of the spines are of great size. There are several large fishes of this genus from Scotland, in the lower compartment of this cabinet, so striking in their appearance, that they seldom fail to arrest the attention of the visitors. Of these, the Holoptychius nobilissimus, from the Old Red Sandstone at Clashbinnie, near Perth, (presented by the Rev. James Noble,) is the most conspicuous. This magnificent ichthyolite is figured in the splendid work of Sir Roderick Murchison, "The Silurian System," Pl. II.; it consists of the body and head, attached to the stone by the dorsal aspect. The body is depressed, and measures twentyeight inches in length, and twelve in breadth. The head is short and obtuse; the lower jaw, the mouth, and the two branchial rays or plates are exposed. The scales are large, and strongly marked with undulating furrows; between the ventral fins and the head there are but fourteen scales. The tail is wanting.

Holoptychius Flemingii, and H. Andersoni, are two species of this genus which occur in the Devonian of Scotland; and there are two large blocks of fawn-coloured sandstone on which are seen lying in relief ten or twelve of these beautiful ichthyolites, whose jetty black finely contrasts with the hue of the surrounding stone. Many are from Dura Den, near Cupar, Fifeshire, the locality where the Rev. Dr. Fleming discovered the first recognised vestiges of this genus, in 1830.

Of the Holoptychius Hibberti, of the coal measures, whose

remains are commonly found associated with those of Megalicthys and Rhizodus, there are in this Case several specimens from Burdie House.

Asterolepis, (starry-scale.)-(A. Asmusii.)-Wall-case B.On the outside of this Case on the top, there is a series of models of the cranial bones of an enormous fish, from the Old Red, near Riga; presented by Sir Roderick Murchison. This Russian ichthyolite is a species of Asterolepis, a genus that has recently been made the subject of an elaborate examination by Mr. Miller, who has published the results in a charming little volume, which I would earnestly recommend the reader to peruse.' These fishes attained a large size; probably from four or five to eighteen or twenty feet in length; for in the Russian model there is a hyoid plate two feet broad, and a maxillary bone twenty-eight inches long.

MACROPOMA MANTELLI.2-Wall-case B. (Nos. 13, 14.)—The group of beautiful chalk fossils, thus labelled, comprises some of the first-fruits of my geological researches in the strata around my native town; several of them are unique, and others are the most instructive examples of this extraordinary type hitherto discovered. The general appearance of these fishes is well shown in the magnificent ichthyolite on the middle shelf (represented on a small scale in Lign. 89); in form the Macropoma resembled a large Carp; like the rest of the Celacanths, the rays and processes are hollow, and the cranium is covered with large granulated plates. The head is very large, being nearly equal to one-fourth the entire length of the body. The brush-teeth are very minute, giving a rasp-like surface to the borders of the jaws, and the conical teeth are small and pointed. The scales are enamelled on the exposed surface, which is covered with tubular spines. opercula are remarkably long. The rays of the fins are large and rigid, especially those of the anterior dorsal, which are armed on each side with rows of sharp spines. The tail is


"Footprints of the Creator, or the Asterolepis of Stromness." By Hugh Miller; p. 71. Ibid. p. 80.

2 Described as Amia? Lewesiensis. "Fossils of the South Downs,"1822; tab. 37, 38. The large specimen figured in Pl. XVIII. I presented to Baron Cuvier, and it is now in the Museum of the Institute at Paris."Wonders of Geology," p. 348; "Medals of Creation," p. 655.

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(nat. size.)

large, rounded, and fan-shaped, with strong equal rays, supported by the inferior and superior spinous processes of the caudal vertebræ.

Air-bladder (or stomach ?) of the Macropoma.- In every example of this fossil fish that I have dissected, there lies within the body, generally nearest the upper or dorsal part of the cavity, a long, hollow, cylindrical substance, often seven inches in length, and 11⁄2 inch in diameter, covered with a thin, brittle, scaly integument, which readily separates into two or three lamina. The anterior part of this organ, which lies close to the posterior margin of the opercular bone, is always imperfect, appearing as if torn or ruptured; the caudal extremity terminates in a cul-de-sac. From the situation and structure of this viscus, I supposed it to be an air-bladder, and described it as such in the "Fossils of the South Downs," (in 1822); but on M. Agassiz's visit to my Museum at Brighton, that eminent naturalist pronounced it to be the stomach. Recent microscopic investigations of the investing integument, have, however, tended to establish the correctness of my original interpretation of the nature of this remarkable body.'

The Macropoma when at maturity, was between two and three feet in length; its massive skeleton indicates a powerful frame, and its thick scales, strong fins, and sharp teeth, prove that it was a voracious fish, capable of overtaking and seizing live prey. I would especially direct attention to the various states of distension in which the air-bladder appears in the specimens here displayed.

1 My youngest son, Mr. Reginald Mantell, first detected the intimate structure of this organ, which has recently been admirably investigated by Prof. Williamson. See an able memoir On the microscopic structure of the scales and dermal teeth of some ganoid and placoid fishes. By W. C. Williamson, Esq. "Philos. Trans." 1849, p. 435. Pl. XLIII, figs. 27, 28, represent the microscopic structure of the scales of the Macropoma and figs. 29, 30, of the air-bladder, described at pp. 462-465. Professor Williamson observes in relation to this fossil viscus-" I am disposed to believe it to have been an organ fulfilling the functions of an air-bladder. Its osseous structure would render it capable of resisting a considerable amount of pressure, and if its patulous extremity were closed up by an elastic valvular membranous appendage, the fish might have regulated its buoyancy by increasing or diminishing the compression of the gaseous contents of the bladder, and thus facilitate its movements in either shallow water or at great depths in the sea.

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