When a portion of the body of an Ichthyolite of this kind is found in a block of chalk, and the fracture of the block appears to be recent, diligent search should be made for the corresponding piece; for it may probably be found to contain the other part of the fish. A splendid specimen of Osmeroides Lewesiensis, more than a foot long, was thus obtained. The quarry-men, in a block of chalk which a recent fall had thrown down, discovered a few inches of the caudal portion of the body of a fish; on the broken surface of the stone, a section of the body was distinctly seen, as in the specimen previously described. Search was made among the fallen masses for the corresponding piece, but without success. Upon observing the face of the quarry exposed by the recent fall, on a projecting block, many yards above our reach, a discoloured spot was indistinctly seen, and it was conjectured that this might prove to be the other moiety of the Ichthyolite. The workmen were directed to preserve this block if possible; but it remained in situ several months, and until the rock was again blasted; when the stone so long coveted rolled away from the fallen mass, and fortunately was soon discovered. It proved to be the corresponding portion of the fish; with the head, opercula, branchial arches, pectoral fins, and the anterior part of the body covered with beautiful cycloid scales. In the preparation of fossils of this kind, glue as the cement, and a paste made of plaster of Paris with thin glue, to fill up the crevices and strengthen the block, are the materials I have employed. The fossil remains of fishes in other rocks require to be extracted and developed in the manner previously directed for the Echinoderms, Cephalopoda, &c. (pp. [332], [497].)
The collector may be reminded, that Otolithes, or ear-stones ([p. 574]), are found in the Crag of Norfolk, and other Tertiary strata; and that Coprolites, associated with minute scales, bones, &c. of small fishes, constitute, in some localities, layers of considerable thickness and of great extent. The "bone-bed" of the Lias, near Westbury, and that of the Ludlow series on the banks of the Teme, near Ludlow,[572] are well-known examples of such a deposit.
[572] See Mr. Strickland’s interesting notice of the distribution and contents of this "bone-bed," in the Quart. Geol. Journ. vol. ix. p. 8
Microscopical Examination.—A few words on the microscopical examination of the remains of fishes may be useful. The structure of the large, and the forms of the minute scales, may be seen by a common lens, and without preparing the specimens. But for the examination of the intimate organization of scales, teeth, &c. the microscope is required; and the method directed for the investigation of flint ([p. 373]) should be employed. The scales, portions of the membranes of the air-bladder, stomach, &c. and thin chips of the teeth, rendered temporarily transparent by oil of turpentine, or permanently so by Canada balsam, should be viewed by transmitted light. But the intricate structure of the dental organs, the medullary canals, and the calcigerous tubes, cannot be successfully investigated without the aid of the lapidary, or the adoption of the process described at page 67 for the preparation of fossil wood for microscopical examination.
BRITISH LOCALITIES OF FOSSIL FISHES.
⁂ The detached teeth, scales, vertebræ, &c. of fishes are so extensively distributed, that there is scarcely a cliff or quarry of fossiliferous rock in Great Britain, that does not contain some examples. The following list of localities must, therefore, be regarded as merely directing the student to a few places, in which particular fossils of this class have been discovered.
Abergavenny. Mt. L. Teeth of Psammodus, Orodus, &c.
Armagh, Ireland. Mt. L. Numerous teeth and spines.
Arundel, Sussex. Cret. Quarries in the neighbourhood; beautiful Chalk fishes.