Chapter XV (2)

The exception above alluded to, is a little Malacopterygian fish, rather larger than a Sprat, called the Capelan (Mallotus villosus), which inhabits the banks of Newfoundland, and other parts of the coasts of the northern seas. Fossil specimens of this fish.[566] occur in nodules of indurated marl or clay, on the coast of Greenland.[567] It is supposed that these Ichthyolites are of very recent date: and that similar fossils are in the progress of formation.

[566] See _Poiss. Foss._ tom. v. pl. lx., in which the skeleton of the recent fish, and specimens of the fossil species, are represented.

[567] Similar fossils have been obtained from the "Drift" on the Saco River, thirty miles north of Portsmouth, New Hampshire. See Lyell’s Second Visit to the United States, vol. i. p. 29.

Ichthyopatolites, or imprints of the pectoral fin-rays of certain fishes. Under this name Dr. Buckland described certain problematical markings observed on a flag-stone from a coal-pit at Mostyn, in Flintshire, and now in the Geological Society’s Museum. It consists of curvilinear scratches or imprints, disposed symmetrically at regular intervals on each side a smooth level space, about two inches wide, which may correspond to the body of a fish, the pectoral fins of which Dr. Buckland suggests were the instruments by which the markings in question were formed.

These scratches follow each other in nearly equidistant rows of three in a row, and at intervals of about two inches from the point of each individual scratch to the points of those next succeeding and preceding it; they are slightly convex outwards, three on each side the median space, or supposed track of the body of the fish. Dr. Buckland, in the memoir referred to, shows that these markings cannot be referable to the imprint of the feet or claws of reptiles, and points out the structure of the bony anterior rays of the pectoral fins, as in certain Siluroid and Lophoid fishes, and in the Climbing Perch (_Anabas scandens_), or the _Hassar_ (_Doras costata_), and refers also to the ambulatory movements of the common Gurnard, in corroboration of this opinion.[568]

[568] Proceedings of Geol. Society, vol. iv. p. 204.

* * * * *

_Geological Distribution of Fossil Fishes._--From the incidental notices of the geological habitats of the fossil fishes enumerated in our survey of this class of beings, the reader cannot fail to have remarked, that the most recent strata abounded in forms related to the inhabitants of the existing seas and rivers; while the most ancient teemed with species and genera of families altogether extinct, or of prodigious rarity in the recent fauna.

In general terms, it may be stated, upon the authority of M. Agassiz, that the Ichthyolites of the Tertiary deposits approach in their characters to the living genera, but all the species are extinct. The newer Tertiary, as the Crag, contain genera common to tropical seas, as the large sharks (_Carcharias_), and eagle-rays (_Myliobates_), &c. In the Eocene, or most ancient Tertiary, as the London and Paris basins, Monte Bolca, &c., many of the Ichthyolites are closely related to recent genera. Of the Chalk fishes, a few only are of recent genera, but the majority are still allied to Tertiary forms. In the Chalk, the _Pharyngognathi_, _Acanthopteri_, and _Malacopteri_ are met with as new types; and indications of the _Hybodontidæ_, _Sauroidei_, and _Cœlacanthi_ (the last derived from the Devonian, and the other two from the Carboniferous Limestone) appear for the last time.

The ichthyic fauna of the Cretaceous deposits is closely related by the majority of its _family_ groups with that of the series of strata from the Lias to the Wealden, inclusive. In and above the Lias all the ganoid fishes are _homocercal_. Below the Lias, the genera and species are far more removed from existing types, and almost all are _heterocercal_.

Of the eight thousand living fishes known to naturalists, three-fourths belong to the Cycloid and Ctenoid orders, and of these no species are known below the Chalk; the other fourth is referable to the Placoids and Ganoids, of which there are comparatively but few existing species. Yet fishes of these two orders almost solely flourished during the ancient Secondary formations; for below the Lias, the predominant recent orders are altogether absent. Beneath the Coal, true carnivorous fishes, with trenchant teeth, are almost unknown; but omnivorous species, with either brush or obtusely conical teeth, and great sauroid fishes, are the prevailing representatives of the class.[569] In fine, the Ichthyolites of the different formations constitute two grand groups, which have their boundary line at the base of the Cretaceous deposits. The first and most ancient comprises the Ganoids and Placoids; the second, more intimately related to existing types, comprehends forms more diversified; these are principally Ctenoid and Cycloid, with a small number of the two preceding orders, which insensibly disappear; and their few living analogues are very distinct from the ancient species. Now, although deductions of this nature may require to be modified with the progress of knowledge, yet the generalizations thus obtained are founded on so vast an accumulation of facts and observations, as to render it improbable that they will be materially invalidated by future discoveries; for they remarkably accord with the results derived from the investigation of the fossil remains of all the other classes of animals. The most modern deposits contain the remains of animals allied to the existing species; the most ancient, of forms altogether extinct, or of excessive rarity in the recent faunas. The discovery of existing species, or genera, in the most ancient strata, would modify, but not destroy, the inferences deduced from the facts hitherto obtained; and every geologist is prepared to find that such may be the case.

[569] In the several chapters on the different formations, as arranged in the _Wonders_, the student will find succinct notices of the distribution of the _genera_ of fishes throughout the fossiliferous deposits. A list of the Chalk species known in 1848 is given at pp. 356-359, _Wond._

Thus of the Sharks, with triangular notched teeth, which are so common in the Tertiary formations, and were formerly unknown in the ancient Secondary, one representative has been found in the Carboniferous system (see p. 595). But, if teeth of this type should hereafter be discovered in every Secondary deposit, the great preponderance of these fishes over the Sauroid in the Tertiary, and in the existing seas, would not be the less remarkable.

* * * * *

On Collecting and Developing Fossil Fishes.--From what has been advanced, the reader will have obtained a general knowledge of the fossil remains of this class that are likely to be met with in particular deposits. Thus, he will expect to find the teeth of large sharks and rays in the Tertiary clays and sands; and skeletons and perfect specimens of numerous Ctenoid and Cycloid fishes in the laminated marls and fine limestones of the same formations. In the Chalk, with numerous teeth of sharks, he may discover splendid examples of Cycloid and Ctenoid fishes; and, in the Wealden, large Ganoidian forms. Passing to the ancient Secondary strata, the extraordinary buckler-headed and Sauroid fishes will arrest his attention; and their vestiges will be found, more or less perfect, in the shales and limestones, and in the indurated nodules of clay and sandstone.

The detached teeth of fishes in Tertiary sands and clays may be easily obtained entire, and should be arranged in the same manner as the shells (see p. 442), either in trays, or on boards. The triangular teeth, with lateral denticles, must be carefully extracted, so as to preserve those appendages on which the specific and generic distinctions of many Ichthyolites depend. M. Agassiz particularly recommends the preservation of all the specimens collected together in the same locality, as many may probably belong to the same individual, and thus the dental organization of the original be determined. Teeth collected from the same stratum in different places, should not, therefore, be mixed together. Several series of the same kind of teeth should be preserved, and as many as possible of each kind; for specimens apparently identical may prove to be highly instructive as a series. I have often had occasion to regret the disposal of supposed duplicates, in my earlier researches, which would have tended to elucidate the characters of those specimens which were retained.

The Ichthyolites, and their detached teeth and fins, in the Chalk and other soft limestones, may be cleared by means of a penknife or graver and small sharp chisels. It is preferable to leave the teeth attached to small blocks of the chalk; as in the examples, figured _Lign. 193_. But to develop the beautiful Chalk Ichthyolites, particularly those of the Osmeroides, Macropoma, &c. some practice and considerable dexterity are required. The compressed fishes, as the Beryx, like those in the Tertiary limestones, often lie in the sedimentary plane of the stone, and may be sufficiently exposed, by a blow of a hammer or a pick, to show the nature of the fossil, and admit of being easily developed. But the fishes with sub-cylindrical bodies very commonly split asunder in a transverse direction: and those with spinous scales, as the Macropoma, adhere so firmly to the chalk, that, to display the external surface of their scales, the surrounding stone must be removed piecemeal, in the manner described for the Chalk crustaceans (see p. 544). The collector who sees the splendid Chalk fishes in the British Museum,[570] and learns that they were found in the Chalk of Kent and Sussex, will be grievously disappointed, upon visiting the quarries from which they were obtained, if he expects to discover specimens with any considerable portion of the scales, or body, exposed. It was many years before the quarry-men acquired the tact they now possess, of detecting, from very slight evidence, the presence of an Ichthyolite in a block of chalk: patches of scales, which the quarry-men called "_bran_," and detached sharks’ teeth, "_birds beaks_," and "_snakes' tongues_," and teeth of Ptychodus, "_slugs_," being the only remains of fishes generally observed and laid aside by the workmen.

[570] _Petrifactions_, pp. 441, 444.

The fossil _Salmon_ or _Smelt_ (see p. 626), which may be considered as one of the most extraordinary of the Chalk fishes found in England, affords an excellent illustration of the mode of developing the Ichthyolites of this formation. This interesting fossil is delineated on a small scale, in three different states, in _Plate II._; and affords a good practical lesson for the young collector. Among some blocks of chalk which a recent fall in one of the quarries near Lewes had brought to light, was a large mass split asunder, and exposing on each corresponding surface an irregular oval marking of a yellowish brown colour; this appearance is represented _Pl. II. _fig._ 1_. Presuming that these markings were produced by a transverse section of the body of a fish, the two blocks were trimmed into a portable size, and accurately cemented together with very _hot, thin, fresh_ glue. When consolidated, some of the chalk was chiselled off in the supposed longitudinal direction of the enclosed fish, and part of the body, covered with scales, was exposed, as _Pl. II. fig. 2_. With the view of ascertaining the extent of the Ichthyolite, some of the surrounding stone was then removed towards each extremity of the block, and traces of the fish were discovered, as shown in the same figure. The task of completely developing the fossil was thus rendered comparatively easy; the chalk was chiselled, cut, and scraped away, till the perfect fish, as seen in _fig._ 3, was developed.[571] The block was then reduced to a convenient size, and the edges sawn smooth. The chalk is easily cut with a carpenter’s saw; the instrument should be short and strong, and the teeth of moderate size.

[571] The figure in _Pl. II._ is too small to convey an accurate idea of this Ichthyolite, which is now in the British Museum; see _Petrifactions_, pp. 445, 446. M. Agassiz’s figure very inaccurately represents the original. A beautiful lithograph of this fish, by Mr. Pollard, of Brighton, was published in the Catalogue of the Mantellian Museum, 1836.

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.

Aust Cliff, near Westbury, Somersetshire. _Lower Lias._
_Pholidophorus_, &c. _Base of Lias._ In a layer called the bone-bed,
containing bones, scales, teeth, and Coprolites of fishes. Teeth of
_Ceratodus_, &c.

Axmouth. _Base of Lias: Bone-bed._ Numerous scales, bones, and teeth.
_Saurichthys_, &c.

Barrow-on-Soar. _Lias._ _Dapedius._

Bracklesham Bay, Sussex. _Eocene._ Magnificent specimens of Rays, as
_Myliobatis_, _Aëtobatis_, and of _Chimæroids_ were collected by the
late F. Dixon, Esq., and are now in the British Museum.

Brighton. Cret. Chalk quarries in the vicinity. _Beryx_, _Dercetis_,
_Saurocephalus_, _Saurodon_, and the common species of teeth, &c.

Bristol. _Mt. L._ The usual species of _Psammodus_, _Orodus_,
_Onchus_, &c.

Burdie-house, near Edinburgh. _Carb._ _Palæoniscus_, _Megalichthys_,
_Holoptychius_, &c.

Caithness, Scotland. _Old Red._ _Dipterus_, &c.

Charing, Kent. Many fishes in the Chalk.

Chatham, Kent. _Cret._ _Beryx_, _Hypsodon_, and the usual teeth, &c.

Cheltenham. _Base of Lias._ In the bone-bed teeth, scales, Coprolites.

Clayton, Sussex. _Lower Chalk._ _Beryx microcephalus_, and other rare
Ichthyolites.

Clifton, near Bristol. _Mt. L._ _Psammodus_, _Orodus_, &c.

Cromarty, Scotland. _Old Red._ _Coccosteus_, _Pterichthys_, &c.

Cuckfield, Sussex. _Wealden._ _Lepidotus, Hybodus, Acrodus._

Cullercoats, Durham. _Permian._ _Palæoniscus_, &c.

Dinton, Vale of Wardour. _Purbeck._ _Leptolepis_, _Ceramurus_, &c.

Downton Hall, near Ludlow. _Devonian._ _Cephalaspis_, _Dipterus_, &c.
_U. Sil._ In a quarry on the banks of the Teme, a fish-bed composed of
scales, teeth, and Coprolites, in Upper Ludlow limestone.

Dudley. _Sil._ _Ichthyodorulites_.

Dungannon, Ireland. _Permian._ Quarry at Rhone-hill; numerous small
_Palæonisci_, _P. catopterus_.

East Thickley, Durham. _Magnesian Limestone._ _Palæonisci._

Glammis, Forfarshire. _Devon._ _Cephalaspis, Gyrolepis, Dipterus._

Gravesend and Northfleet. Chalk-pits rich in fish-teeth, &c.

Hastings. _Wealden._ _Lepidotus, Hybodus._

Ilminster, Somerset. _Upper Lias._ _Pachycormus_ and _Leptolepis_.

Leeds, Middleton Quarry. _Carb._ Layers of _fish-coal_, abundance of
remains of _Megalichthys_, _Holoptychius_, &c. (_Geol. Proc._ iii. p.
153.)

Lewes, Sussex. _Cret._ All the fishes of the British Chalk. See
_Wond._ pp. 356-359.

Lyme Regis. _Lias._ _Dapedius_, _Hybodus_, _Squaloraia_; and numerous
other species and genera.

Newhaven, near Leith. _Carb._ On the shore, nodules of ironstone with
fishes and Coprolites. _Amblypterus, Palæoniscus._

Sheppey, Isle of. _Tert._ Numerous teeth of Rays, Sharks, &c., and
other Ichthyolites in great abundance.

Shotover, near Oxford. _Kimmeridge Clay._ _Ischyodus_, _Hybodus_, &c.

Southend, Essex. _Eocene._ Fish-bones and teeth (_Pisodus_, &c.) are
found on the shore along the foot of the cliff.

Speeton, Yorkshire. _Galt._ _Macropoma Egertoni_; and many other
fishes.

Steyning, Sussex. _Cret._ In the marl-pits, Coprolites and teeth of
Sharks are abundant.

Stonesfield. _Great Oolite._ _Hybodus_, _Lepidotus_, _Leptacanthus_,
&c.

Swanage. _Purbeck._ _Lepidotus_, _Hybodus_, _Ophiopsis_, &c.

Thurso, Scotland. _Devonian._ _Asterolepis_, &c.

Westbury, near Bristol. _Base of Lias._ Bone-bed with numerous remains.

Worthing. _Cret._ Beautiful Chalk fishes in the neighbouring quarries.

FOREIGN LOCALITIES.

⁂ Although the present work is expressly designed as a guide to the British collector, I am induced to subjoin a few foreign localities of Ichthyolites, that lie within the reach of the continental tourist. A detailed account of the most celebrated sites is given by M. Agassiz, Poiss. Foss.

Aix, in Provence. _Tertiary._ Some of the beds of gypseous marl
contain numerous species in abundance.

Eisleben, Upper Saxony. _Permian._ Numerous Ichthyolites in dark shale.

Glaris, Switzerland. _Cret._ Immense numbers of fishes in dark schist.
The specimens are often contorted, from the contraction of their
bodies, during decomposition.

Maestricht (St. Peter’s Mountain). _Upper Cret._ Numerous teeth,
vertebræ, &c. of fishes of the Cretaceous epoch. See _Wond._ p. 309.
Mansfeld, in Thuringia. Permian. Fishes in copper-slate, in great
numbers; many extremely beautiful.

Monte Bolca, or Vestena Nova. _Tert._ The richest mine of Ichthyolites
in the world. A catalogue of the numerous genera and species found
in this celebrated locality, is given in _Poiss. Foss._ tom. iv. pp.
33-52.[573] See _Wond._ p. 265.

Mount Lebanon, Asia. _Tert._ Numerous Ichthyolites, in great
perfection.

Œningen. _Tert. fresh-water._ Many kinds of fishes of the same genera
as those which inhabit the great European lakes; as the Perch, Salmon,
Eel, Pike, Carp, &c. A list of these Ichthyolites will be found in
_Poiss. Foss._ tom. ii. part ii. p. 78. See _Wond._ p. 263.

Saarbrück, in Lorraine. _Carb._ _Amblypterus_, and other Carboniferous
fishes.

Seefeld, in the Tyrol; on the principal road from Insbruck to Munich.
_Lias._ Abundance of fish in bituminous slate.

Stabia, Italy, at Torre d’Orlando, near Castellamare. _Oolite._
Beautiful fishes in fissile limestone.

Solenhofen. _Oolite._ Numerous Ichthyolites; many in great perfection.
See _Wond._ p. 513.

[573] It is necessary to caution the collector against the frauds practised by the quarry-men, and dealers in fossils, at this and other celebrated foreign localities. Specimens, apparently perfect, are ingeniously constructed from the fragments of various examples. The head of one fish, the body of another, decorated with the fins of a third, and perhaps the tail of a fourth, of different species, or even genera, are dove-tailed together, coloured, and varnished, so as to deceive the common observer, and, occasionally, even the experienced collector. Sponging the specimens with cold water will often detect the imposition; for the colour if artificial will be removed, or rendered paler, while the same process will heighten the natural tints. At Pappenheim, Solenhofen, and other places, where fossil crustaceans, as Shrimps, Prawns, &c. are found in such perfection, the imprints of good specimens are often coloured, and offered for sale; a wet sponge will speedily detect the imposture.