Chapter 35

[541]Odontography, p. 72.

Lign. 198. Gyrodus Murchisoni[542](G. A. M.)Oolite?Russia.(Collected by the late Stephen Cattley, jun. Esq.)Fig.1.—The vomerine bone of a fish, with five rows of teeth; seen from above; many of the crowns of the teeth are worn away by use, and the large pulp-cavities, filled with white spar, are exposed; as ata.2.—Lateral view of the same.a.One of the pulp-cavities filled with spar.

[542]It is with peculiar pleasure that I inscribe this new species ofGyrodusto Sir R. I. Murchison, in commemoration of those extended and successful geological researches in the Russian empire, which have conferred additional honour on his distinguished name.

The fishes of the genusGyrodushave the body large, flat, and elevated; the dorsal and anal fins are very long; and the tail is forked, with equal elongated lobes. The scales are laterally connected by strong processes, as in Lepidotus.

Other genera related to the foregoing occur in the Oolite; as for example, Microdon, thus named from the smallness of its very numerous flat angular teeth, arranged in many rows;Placodus, in which the teeth are few, flat, and of great size;[543]andPlatysomus(flat-body), with orbicular, clavate, teeth.

[543]Odontography, pl. xliii.fig.1, and pl. xxx.fig.2.

In these fishes, also, the dental organs are well adapted for the comminution of shell-fish, and other hard bodies.

Cephalaspides of the Devonian System.—The remains of the three genera of Ganoid fishes that we have now to notice are of a very remarkable character, and are found exclusively in the Devonian or Old Red system; most frequently in Scotland, but also in other parts of the British Isles, and in Europe and America. These fishes agree in one general character, that of having extensive osseous plates, or scutcheons; their general aspect will be understood by reference toLign.199, 200, 201. There are no vestiges of the bodies of the vertebræ, which, therefore, were probably cartilaginous. These fishes constitute a distinct family with the nameCephalaspides, from the character of the first genus we propose to describe.

Lign. 199. Cephalaspis Lyellii.(1/4nat. size.)Devonian.Forfarshire.Crushed specimen; seen from above.

Lign. 200. Cephalaspis Lyellii.(1/4nat. size.)Devonian.Glammis, Forfarshire.Lateral view, showing the produced dorsal lobe of the tail.

Cephalaspis Lyellii.Lign.199, 200.—The most striking feature in the Ichthyolites of this genus is the enormous scutcheon, or buckler, which forms the head, and is prolonged posteriorly into two lateral horns or points; this part so closely resembles the cephalic shield of certain trilobites (seeLign.175), that the first found specimens were supposed to be the remains of unknown crustaceans. The nameCephalaspis(buckler-head) is derived from this character. This remarkable appearance is occasioned by the intimate anchylosis of all the bones of the cranium. The body of these fishes is relatively smaller than the head; it has one dorsal fin, and terminates in a tapering tail, supportinga fin. There are two small eyes, placed towards the middle of the head. The body is covered with rhomboidal scales; and the head with discoidal scales, which are highly ornamented with radiated markings[544](Ly.p. 344,fig.396). There are four species of Cephalaspis at present known.

[544]Poiss. Foss. tom. ii. p. 135.

The other genera are equally unlike any recent types of the class of fishes. No perfect examples have been found, and some parts of their structure are still unknown; the annexed figures,Lign.201, have been drawn by Mr. Dinkel (the eminent artist employed by M. Agassiz), with scrupulous accuracy, no part being introduced which is not clearly demonstrated in some one specimen; and the form of the scutcheons is made out very distinctly, to aid the collector in discriminating the detached plates, which are the most common relics of these singular beings.

Pterichthys cornutus.[545]Lign.201,fig.1.—This fish is distinguished by its two wing-like lateral appendages; whence the name of the genus (winged-fish). These processes, like the spines on the gill-covers of the common Bullhead (Cottus gobio), are weapons of defence. In some specimens they are extended at right angles to the body (Ly.p. 345,fig.400).

[545]The first fish of this genus was discovered by Mr. Hugh Miller, in whose charming little work, "The Old Red Sandstone; or, New Walks in an Old Field," will be found a very graphic description of the Old Red fishes; I know not a more fascinating volume on any branch of British geology. Consult also Sir P. Egerton’s elaborate paper on thePterichthysin the Geol. Journal, vol. iv. p. 302.

The head and anterior part of the body are covered with large angular tuberculated scutcheons. The under surface of the body is flat and protected by five plates, a quadrangular plate occupying the centre. The upper part of the body is convex; the form and disposition of the dorsal scutcheons are shown inLign.201,fig.1. There are twoeyes, which are placed in front of the lateral spines: seefig.1. The tail is of an angular form, and as long as the body; it is covered with scales, and considered by M. Agassiz to have been the only instrument of locomotion. The British species of this genus, of which ten are known, are all very small, varying in length from one to ten inches.

Lign. 201. Fossil Fishes of the Devonian System.(Drawn by Mr. Joseph Dinkel.)Fig.1.—Pterichthys cornutus, seen from above.2.—Coccosteus oblongus.These figures are restored with great care, from the best preserved specimens hitherto discovered.

These figures are restored with great care, from the best preserved specimens hitherto discovered.

Coccosteus oblongus.Lign.201,fig.2.—The fishes of this genus, as may be seen by the lignograph, very much resemble those of Pterichthys; in both the osseous scutcheons of the body are very similarly disposed. InCoccosteus, the head[546]is somewhat rounded; slight rounded notches on the edge of the buckler indicate the place of the eyes on the sides of the head. There is no indication of lateral spines. The tail is very long, covered with scales, and supports a fin. The plates of the body are tuberculated, as in Pterichthys. There are six or eight teeth on each half of the lower jaw (and probably as many on the upper), with a curious group of teeth situated on its symphisis. The teeth are chiefly composed of bone, passing into dentine at their surface.[547]

[546]This is of course only the cranial buckler of the animal, for, as Mr. Hugh Miller observes, "of the true internal skull there remains not a vestige. Like that of the Sturgeon, it must have been a perishable cartilaginous box."—Miller’s Foot-prints, p. 50.[547]Miller, Rep. Brit. Assoc. 1850. Transact. Sect. p. 92. In the Annals of Natural History for November, 1848, Professor M‘Coy has given a corrected outline of the carapace, or bony cephalo-thoracic casing, of the Coccosteus. See also Miller’s Foot-prints,fig.11.

[547]Miller, Rep. Brit. Assoc. 1850. Transact. Sect. p. 92. In the Annals of Natural History for November, 1848, Professor M‘Coy has given a corrected outline of the carapace, or bony cephalo-thoracic casing, of the Coccosteus. See also Miller’s Foot-prints,fig.11.

These fishes are from a few inches to two feet in length; six species have been discovered; and their remains are the most abundant of the Ichthyolites of the Old Red. Patches of detached scales, and isolated osseous plates, are very frequent in the sandy cornstones, and the subcrystalline masses of limestone. These fragments are usually of a brilliant blue or purple colour; and, strongly contrasting with the dull red tint of the surrounding rock, are easily recognised. The colour is supposed to be due to the presence of phosphate of iron, which has communicated a similar tint to the Ichthyolites of the Caithness Schist.[548]

[548]Murch. Sil. Syst. p. 588; see also a detailed description of the Cephalaspis, Holoptychius, and other Devonian Ichthyolites, by M. Agassiz, ibid. p. 589-601.

Fossil Sauroid Fishes.(Poiss. Foss.tom. ii.)—The family of Ganoid, fishes termedSauroid, or lizard-like, by M. Agassiz, are so named in consequence of certain peculiarities in their organization which are found in no other animals of this class, but exist in reptiles. There are but two living genera; namely, theLepidosteus, of which there are many species that inhabit the rivers of America; and thePolypterus, that contains 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, plesiosaurus, &c.; 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. Even in the soft parts many analogies to reptilian structure are seen; thus the Lepidosteus has a glottis, as in theSiren; 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 most ancient marine fauna, whose remains abound in the Secondary formations. Their relics 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 generally supposed to belong to crocodiles. The scales are flat, rhomboidal, and parallel to the body. The recentLepidosteus osseus, of North America, affords a good illustration of the fossil genera; a reduced figure of this fish, fromPoiss. Foss., will be found inBd.pl. xxviia.; and teeth of some fossil Sauroids are representedBd.pl. xxvii.

The teeth of the Sauroids consist of two kinds; namely, large pointed striated cones, and numerous small brush-teeth. The intricate structure of the conical teeth of theStony-gar, or Lepidosteus, is very remarkable, and presentssome analogy to that observable in the dental organs of the Labyrinthodon, an extinct genus of reptiles, of which we shall treat in a subsequent chapter. The tooth consists of a large conical pulp-cavity, surrounded by a mass of dentine, which is plicated longitudinally, its folds giving to the pulp-cavity an appearance of being divided into parallel longitudinal branches; resembling, in this respect, the base of the tooth of Ichthyosaurus, as shown in a transverse section,Pl. VI. fig. 9. If we imagine these folds to be multiplied, and to have more inflections, and the pulp-cavity to be reduced in its proportions, we shall have the elegant organization of the teeth of theLabyrinthodonts(seePl. VI. fig. 3b). The dentine is composed of very minute calcigerous tubes, which pass off at right angles from the pulp-cavity to the periphery; and it is covered by a layer of cement, or coarser dentine, which is encased in a coat of enamel, forming the external investment of the tooth.[549]The long conical teeth are implanted inalveolior sockets, to the walls of which they are anchylosed at their base.

[549]These remarks are based on M. Agassiz’s description and my own observations. An interesting paper, "On the Microscopic Structure of the Teeth of theLepidostei, and their analogy with those of theLabyrinthodonts, with a plate," byDr. Jeffries Wyman, will be found in Amer. Journ. of Science, October, 1843, p. 359.

Lepidostei.—This family, having the above described recentLepidosteusfor its type, comprises several genera, and is represented in all the formations from the Tertiary to the Coal-measures inclusive. TheLepidosteusitself has left its remains in the Eocene tertiary of England. The Lepidotus (before described,p. 604,) ranges from the Chalk to the Lias; thePholidophorusandDapedius(p. 603) abound in the Lias; the latter being found also in the Wealden, and the former in the Oolite and Purbeck; and thePalæoniscus(seep. 601) is a well-known Permian and Carboniferous form.

Sauroidei.—The remains of the Sauroids proper occur in the Chalk, Purbeck, Oolite, Lias, Permian, and Carboniferous rocks. The great strength and size of some of these teeth prove that the seas of those remote periods were inhabited by voracious fishes of enormous magnitude. SeePetrif.pp. 432,et seq.

The teeth and jaw of a gigantic sauroid (Megalichthys), from the Carboniferous strata at Burdie-house, are figuredBd.pl. xxvii.; the sections of the teeth shown in figs. 13, 14, of that plate, illustrate the size of the pulp-cavity and the thickness of the layer of dentine. These remains were associated with the plants and crustaceans previously described; an assemblage of fossils indicating a lacustrine or estuary formation. Similar teeth have been found in the cannel-coal of Fifeshire.

In the Upper Lias of Ilminster, Somerset, the nodular calcareous rock is rich with the remains of thePachycormus, many fine specimens of which Mr. C. Moore, of that town, has successfully worked out from their stony encasement, exhibiting the gaping, contorted fish, as it died in the convulsive throes of suffocation in the muddy sea. The little sauroidLeptolepis, of the Lias and the Purbeck, is also abundant in the above mentioned locality.

In the lithographic stone of Solenhofen, and in the Purbeck strata, Oxford Clay, and Lias of England, occur specimens of a sauroid fish remarkable for the extreme shortness of the lower jaw, and the prolongation of the upper into a beak; it is namedAspidorhynchusby Agassiz. The figure of this fossil fish is contrasted on pl. xxviia.Bd.with that of its recent ally, theLepidosteus.

In the Shanklin sand and in the Galt of Kent and Sussex, large, conical, striated teeth belonging to sauroid fishes are occasionally found. They invariably occur detached, and no portion of the jaws has been observed. In the Chalk of Sussex several fine sauroid fishes have beendiscovered; such as theLophiostomus,[550]Belonostomus,[551]andCaturus; the last two of which are found in the Oolite and Lias also. These have been described and figured in the late Mr. Dixon’s "Geology and Fossils of Sussex."

[550]Geol. Surv.Dec. 6. pl. x. xi.[551]Petrif.p. 431.

[550]Geol. Surv.Dec. 6. pl. x. xi.

[551]Petrif.p. 431.

TheSauroidei-dipterini[552]are found almost exclusively in the Devonian formation.Osteolepis,Diplopterus, andDipterusare characteristic members of this family. Interesting descriptions and instructive figures of the structure of these genera are given in Mr. Hugh Miller’s late work, "Foot-prints of the Creator, or the Asterolepis of Stromness," at pp. 50 to 61.

[552]The characters of the scales of this and the next family, as well as of the Acanthodei, are succinctly given in Miller’s Foot-prints of the Creator, pp. 30,et seq.

Cœlacanthi.—This is a numerous family of sauroid fishes, that have derived their name,hollow-spine, from the central cavity in the fin-rays, which, however, may have had originally cartilaginous cores. They are found from the Devonian to the Cretaceous series. In the former, one of the most remarkable is the genusHoloptychius, distinguished by the peculiar structure of the scales; the enamelled surface of which is covered by undulated furrows. The whole body is covered by thick enamelled scales of this kind. A splendid specimen, twenty-eight inches long, and twelve wide, is figuredMurch. Sil. Syst.pl. ii.bis.Scales have been found exceeding three inches in length, by two and a half in width; which must have belonged to a fish of great magnitude.Ly.fig. 395.

In the Old Red Sandstone of Elgin, at a quarry at Scat-craig, some peculiar teeth occur, which possess a very remarkable structure, and have been referred to a genus of sauroid fishes, which, from the dendritical or arborescent disposition of the calcigerous tubes, Prof. Owen has namedDendrodus. These teeth are of a conical form, slightly curved,and solid throughout. On the external surface they are finely striated longitudinally, and have two opposite vertical ridges; the base is rough, and its margin rounded, as if for attachment to a shallow socket. The largest specimen is one and a half inch in length. In thin sections, viewed microscopically by transmitted light, there is a central pulp-cavity, of small size; the medullary canals pass into a few short ramifications, like the branches of a shrub, and these are distributed into irregular dilatations, simulating leaves, which resolve themselves into radiating bundles of calcigerous tubes; a portion of a transverse section[553]is shownPl. VI. fig. 8.

[553]Odontography, pl. lxii. Bfig.2; and Cycl. Anat.Art.Teeth.

Lign. 202. Asterolepis.Devonian.(1/2nat. size)Inner side of portion of the lower jaw.(After Miller.)

ASTEROLEPIS.

In Mr. H. Miller’s charming work just referred to we have a full and clear account of the singular fossil fish theAsterolepis. Remains of this gigantic Ganoid were first found in Russia.[554]Its name is derived from the stellate markings on the dermal plates of the head, which are of great size, and form a strong expanded buckler, the orbits of the eyes being situated near the anterior border. (See Miller’sAsterolepis, pp. 74,et seq.figs. 27-29.)Lign.202shows a part of the lower jaw of this fish, seen on the inside. Along the upper margin are seen a "thickly set row ofsmall broadly-based teeth,"—these are ordinaryfish-teeth; and behind this edge-row of small teeth,b, there occur "a thinly set row of hugereptile-teeth, based on an interior platform of bone, which formed the top of the cartilage enclosing box composing the jaw." (Miller.) These large teeth,a a, are longitudinally striated, and generally bear two sharp lateral cutting edges.[555]

[554]Casts of the fossil bones from Russia are in the British Museum;Petrif.p. 435.[555]The microscopic structure of both kinds of teeth is elegantly figured in Mr. Miller’s work, pp. 81, 82.

[554]Casts of the fossil bones from Russia are in the British Museum;Petrif.p. 435.

[555]The microscopic structure of both kinds of teeth is elegantly figured in Mr. Miller’s work, pp. 81, 82.

Macropoma Mantelli.Wond.p. 348. (Foss. South D.tab. xxxvii. xxxviii.;Petrif.p. 436,Lign.89.)—This Cœlacanth fish is from one to two feet in length, of an elongated fusiform shape, with a large head and two dorsal fins; the anterior fin is imbedded, and has seven or eight strong spinous rays, the first two of which have numerous spines. The opercula are very long and large (hence its name); the scales[556]are garnished with adpressed spines, disposed in semicircular rows (seeLign.185,fig.2). The teeth are small, conical, and numerous.

[556]See Prof. Williamson’s Memoir, Philos. Trans. 1849, p. 435; pl. xliii. figs. 27, 28.

Several specimens of this fish are almost perfect. The bones of the cranium, the jaws, teeth, opercula, branchial rays, palatine arches, the surface of the body covered with scales, all the fins, the pelvic bones, the vertebræ and their apophyses, all remain.

In one example, the vomer, covered with minute teeth, is exposed. But the most extraordinary fact relating to these Ichthyolites, is the preservation, in every specimen, of the air-bladder;[557]even its membranes remain, and separate in flakes; and the ramification of the minute vessels is visible under a high magnifying power. In some instances this bladder is displaced and much distended; but in general it occupies its natural position, and retainsits elongated, sub-cylindrical form, with a few annular constrictions or folds.

[557]See Williamson,op. cit.pp. 462-165, and figs. 29, 30.

COPROLITES. COLOLITES.

Coprolites.Lign.139,figs.1, 2.—In more than one example the solid earthy residue of digestion, in small lumps or pellets, of a conical form and spirally convoluted, lies in the abdomen of these fossil fishes. Fossil excrementitious substances of this kind are termedCoprolites(Bd.p. 198, pl. xv.); they occur in many deposits, and belong not only to fishes, but to large reptiles and other animals.Lign.139, p. 432,fig.1, represents the coprolite of aMacropoma; andfig.2, that of a species ofShark, from Hamsey. The convoluted appearance of these bodies arises from the peculiar organization of the intestinal canal of the original fishes, in which, as in the recent Dog-fish, a portion of the intestine was spirally twisted, the tube forming several gyrations; and the passage of the calcareous substance through this constricted canal gave rise to the structure observable in the coprolites. In the Macropoma the gyrations appear to have been few; seldom more than five or six turns being apparent. In the fossil Sharks the convolutions are more numerous, ten or twelve occurring in the length of an inch. In many of the coprolites, the impression of the mucous or lining membrane of the intestinal canal may be detected. Some of the coprolites of the Macropoma are not convoluted; probably from having occupied the upper part of the digestive tube, and therefore not having been moulded in the spiral part. (SeeGeol. S. E.p. 145.Foss. South D.tab. ix.) Minute scales and bones of fishes are occasionally imbedded in the substance of the coprolites, affording evidence of the carnivorous habits of the Macropoma.

Cololites.Bd.pl. xva—It will be convenient to notice in this place those curious fossils which occur in detached masses in the limestone of Solenhofen, and used to be known to collectors by the termlumbricaria, from thesupposition that they were petrified earth-worms. An excellent representation of a fine specimen is given by Dr. Buckland in the plate referred to above. These convoluted bodies M. Agassiz, with his wonted sagacity, has ascertained to be the intestines of fishes; and has therefore named themCololites. Although generally found isolated, specimens occur in which they are imbedded, like the coprolites of the Macropoma, in the abdominal region of fishes. The frequent occurrence of theCololitesapart from the body, is explained by the usual process of decomposition in fishes. M. Agassiz remarks that dead fish always float on the surface of the water with the belly uppermost, until the abdomen bursts from distention. The small intestines are then expelled by the evolved gases through the aperture, and soon become detached from the body. I have observed indistinct traces of similar remains in the beds of chalk in which fossil fishes most prevail. Dr. Buckland mentions the discovery, by Lord Greenock, of a mass of petrified intestines distended with coprolite, and surrounded by the scales of a fish, in a block of coal-shale from the neighbourhood of Edinburgh (Bd.p. 199).

Dercetis elongatus.Wond.p. 349.—Before proceeding to the investigation of examples of the next order, I will describe a highly interesting Ichthyolite, which in a mutilated state is extremely common in some of the chalk strata of the South-east of England; it is noticed inFoss. South D.p. 232. This fish is placed by M. Agassiz in his family of ganoidians, termedScleroderms; and he mentions that another species has been found in the chalk of Westphalia. TheDercetishas a very elongated body, with a short head terminating in a pointed beak; the upper jaw is a little longer than the lower, and both jaws are armed with long, conical, elevated teeth, and several rows of very small ones. On each side of the fish there are three rows of osseousscutcheons like those of the Sturgeon (seeWond.p. 349); the body was also covered with numerous small scales. From the form of the body somewhat resembling that of the eel, being very long, and sub-cylindrical in uncompressed examples, the specimens are generally called "petrified eels" by the quarry-men. The examples usually found consist of the elongated body, more or less compressed, and irregularly covered with patches of scales confusedly intermingled; among which traces of the scutcheons may sometimes be distinguished. These specimens occasionally exceed two feet in length, by one or two inches in breadth; with neither extremity perfect, and without any vestige of the fins.[558]The example figuredWond.Lign.74, is the only instance in which I have seen the cranium perfect. The scutcheons in the Westphalian species have a prominent longitudinal ridge or keel, and their surface finely granulated; they are so large that the whole body of the fish is covered with them.

[558]SeeFoss. South D.pl. xl.fig.2, and pl. xxxiv. figs. 10 and 11.

CTENOID FISHES.

Fossil Ctenoid Fishes(Poiss. Foss.tom. iv.).—The fishes of this order have imbricated laminated scales, the posterior margins of which are round and finely pectinated;i. e.divided into little teeth, like a comb. These scales are nearly circular, but more or less elongated; and, as the laminæ of which they are composed successively diminish from the lowermost to the uppermost, the pectinated margin of each being apparent, the surface is very scabrous; the front edge is sinuous. The commonPerchis the type of the Ctenoidians. The teeth of these fishes are invariably small, and either villous or brush-like.

From the numerous fossil genera I select, in illustration of the characters of this order, theBeryx; of which four species occur in the English Chalk, and three others in the Chalk of Bohemia and Westphalia. Of this genus, which is closely related to the Perch (Perca), two living speciesinhabit the seas of Australia. The bones of the skull have dentated crests; the dorsal fin has spinous rays in front, which are united to the soft rays; the margin of the caudal fin has little spinous rays.

The Beryx is one of the most ancient representatives of the Perch tribe, and of the Ctenoid order.

Beryx Lewesiensis.[559]Wond.p. 351;Petrif.Lign.90.—This is one of the most common of the Ichthyolites of the Chalk of the South-east of England; it is called "Johnny Dory" by the quarry-men; the specimens are from six to twelve inches long. It occurs also in the Chalk of Westphalia. The outline of the perfect form of this species,Wond.p. 351, by Mr. Dinkel, conveys an accurate idea of its external characters. It has one dorsal fin, with several spinous rays in front of the soft ray. The head is very large, and the opercular pieces are ornamented with sculptured rays; the margins of the jaws are covered with a broad band of brush-teeth. The orbit is large, and often contains the capsule (sclerotica) of the eye. The rays of the gills are short and thick, five are preserved in some examples. The scales are very large; about twenty-five in the median row; their posterior margins have several concentric rows of spines (seeLign.185,fig.3, p. 567). The lateral line is often distinctly apparent, in the form of a tube, contracted behind and expanded in the centre of the scale. The vertebral column is composed of large short vertebræ, with very long apophyses; the ribs are slight.

[559]The fossil discovered by me, and figured inFoss. South D.tab. xxxvi. was the first perfect fish obtained from the Chalk. This fish was first described by me,Foss. South D.tab. xxxv. xxxvi. asZeusLewesiensis; M. Agassiz has very properly referred it to the genusBeryx; but he has also substituted another specific name; which is wholly unwarrantable, for that first imposed ought to be retained; seep. 518, note.

Beryx superbus.—This is a larger species, sometimes thirteen inches long, with very large and broad scales. Ithas been found in the lower chalk at Lewes. See Dixon’sFoss. Sussex, tab. xxxvi.fig.5.

Beryx radians.Wond.p. 350.—This species is smaller, and relatively longer, thanB. Lewesiensis; it generally occurs in the Chalk-marl, and is invariably of a very dark colour, the scales having a polished or glossy aspect. The scales are small, with a simple row of diverging spines on the posterior edge. The scales of the lateral line are peculiar; the mucous canal is not formed of a series of simple tubular cylinders, as inB. Lewesiensis, but is divided into several branches, as may be seen with a lens of moderate power. There are more than thirty scales in the length of the lateral line.

Beryx microcephalus(Poiss. Foss.tom. iv. tab. ivc.; and Dixon,Foss. Sussex, tab. xxiv.fig.3).—This fish is distinguished by its slender form, and the extreme smallness of the head, as the name implies. The scales have one row of very thick spines on the posterior margin; they are more elevated, and shorter than inB. radians; those of the lateral line are pierced by an elongated conical tube, and are not ramified as in the last species. This ichthyolite, like theB. radians, occurs in the Chalk-marl, and in a similar state of mineralization.

Smerdis minutus.Lign.203.—A pretty ctenoidian fish, from one to three inches long, about the dimensions of a perch a year old, is very common in the marls of Aix in Provence,Wond.p. 260; and many are often found grouped together in every variety of position. This species is characterised by the elevated anterior rays of the dorsal, and the wide and very forked caudal fin.

Several ctenoidian and cycloidian fishes have been found in the north of the Brazils, by Mr. Gardiner, in strata probably of the Cretaceous epoch.

Fossil Cycloid Fishes.(Poiss. Foss.tom. v.)—This order comprises the fishes possessing scales of a cycloid, or circular,form, with smooth margins, and composed of plates of horn or bone, without enamel. It contains numerous families, including theScaroids, or Parrot-fishes, and theScomberoids, or Mackerel tribe, which are Acanthopterygians, theLucioids, or Pikes,Clupeoids, or Herrings,Salmonoids, or Salmon tribe, and theCyprinoids, or Carps, which are Malacopterygians, as well as other families. The fossil remains of this order are exceedingly numerous, particularly in the Tertiary and upper Secondary deposits. A genus ofSalmonidæ, discovered in the White Chalk of Sussex, will serve to exemplify the characters of the fossil cycloidian fishes.

Lign. 203. Smerdis minutus.Eocene.(nat. size.)Aix in Provence.

Osmeroides.Plate II.andWond.p. 344, 347.—Two species of this genus occur in the Chalk, near Lewes; and principally, if not exclusively, in the Lower Chalk, without flints. They are exceedingly beautiful Ichthyolites, and are almost invariably found with the body but little compressed; the fish, in many examples, is as round and perfect as when living. The entire cranium, the opercula and branchial rays, and all the fins are preserved in someexamples. These fishes belong to the Salmon family,[560]and are nearly related to theSmelt(Osmerus); whence the name of the genus. There are two species, easily distinguishable. The first (O. Mantelli,Pl. II.) has a short, sub-cylindrical body, and seldom exceeds eight or nine inches in length; the other (O. Lewesiensis) has an elongated and elliptical body, and sometimes attains a length of fourteen inches. The dorsal fin too in this species has more rays than in the other. The fossil figured inPl. II.. is a very remarkable specimen of the first species. It is nine inches in length; and the chalk has been cleared away, so as to expose the entire fish, six inches in relief above the surface of the block,Petrif.Lign.92, p. 445. The fish is lying on its back, with the mouth open, and the opercula, or gill-covers, and the branchial arches expanded; the pectoral and ventral fins, and the dorsal fin, are in their natural position; the five rays of the dorsal are erect; of the caudal fin, or tail, but slight indications remain. There is but one dorsal fin; but in a specimen ofO. Lewesiensisthere is a trace of the little adipose process observable between the dorsal fin and the tail, as in the recent species ofSalmonidæ. A magnified view of one of the scales is representedLign.185,fig.4, p. 567.

[560]They were first described by me inFoss. South D.p. 235, tab. xxxiii. and xl. asSalmo Lewesiensis.

Of theCyprinoids, or fishes of the Carp family (Malacopterygians), the recent species of which are inhabitants either of fresh-water, or the brackish waters of the mouths of rivers, many fossil species occur in the fluviatile and lacustrine deposits of the Tertiary formations. In their character of omnivorous fishes, the Carps then, as now, formed the principal mass of the finny population of the lakes, and in their turn served as food to the carnivorous tribes, as the pikes, eels, &c. Several species are found in a beautiful state in the schists of Œningen, and in theTertiary marls at Aix. Many of the layers of marl at the latter locality are covered with groups of fishes of the familyCyprinodonts, the recent species of which are of a small size, and inhabit the fresh-water lakes of temperate zones.Lign.184, p. 562, represents a portion of a large slab of marl in the cabinet of Sir R. Murchison, which is covered with scores of a species resembling a recent fish (Lebias) in the profile of its head, and the form of its fins. It is namedLebias cephalotes, from the relative largeness of its head. The black appearance of the abdomen in many of these Ichthyolites indicates the original situation of the intestines and of the liver, which is largely developed in the fishes of this family, and contains much colouring matter.

Saurocephalus and Saurodon.Lign.204.—In the same quarry, near Lewes, from which the first entire fish of the Sussex Chalk was obtained, teeth of a very peculiar character were, many years since, occasionally discovered.[561]These teeth are of a lanceolate form, much compressed; with entire, sharp edges, terminating in a point; the fang is single, and broad; the surface of the crown is glossy, and marked with fissures filled with chalk (seeLign.204,fig.1). Teeth of this kind, attached to portions of the jaw, were subsequently found in the Chalk at Brighton and Lewes. Similar remains were collected from the Cretaceous marls of Missouri and New Jersey, in the United States. The American specimens comprised two closely allied genera, which, from the supposition that the fossils were the relics of reptiles, were respectively designatedSaurocephalusandSaurodon.[562]Examples of the teeth and jaws of both genera have been discovered in the Sussex Chalk (seeLign.204).

Back to Index Next