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ORGANIC REMAINS. 



CLASS IV. FISHES. 



For the characters of the order?, see Ichthyology. 



The history of fossil fishes is more imperfect than any other 

 department, iiwinir to so little being known respecting the liv- 

 ing 1 species ; but the cloud which has so long 1 hidden it is likely 

 soon to be dispelled by the able and important investigations of 

 professor Agassiz, who has already ascertained and described 

 two hundred genera, containing upwards of eight hundred and 

 fifty species of fossil fishes. These discoveries are of much im- 

 portance to the iri-oloiri-t, and will enable him to follow this 

 nigh class of vertebral animals, through the whole series of 

 geological formations. 



The most extensive deposits of fossil fishes in Europe, are the 

 coal formations of Saariirurk, in Lorraine ; the bituminous 

 slate of Mansfield, in Thuringia ; the calcareous lithographic 

 slate of Solenhafen : the compact blue slate of Garis. the lime- 

 stone of Monte Bolea, near Verona ; the marlstone of Oen- 

 ingen, in Switzerland ; and of Aix, in Provence. 



Of the existing genera of fishes, no species has been found 

 in a fossil condition in any stratum older than the chalk forma- 

 tion. In the inferior chalk, there has been met with a species 

 belonging to the living genus, Fistularia; in the true chalk, 

 five ; and in the tertiary strata of M. Bolea, species belonging 

 to thirty-nine living genera have been ascertained; and thirty- 

 eight which are extinct. 



Agassiz has founded his classification of recent fishes upon 

 the characters of their scales, which is peculiarly applicable to 

 fossil fishes. So certain is the criterion, that from a single scale 

 he will often be able to ascertain, with certainty, the genus, 

 and also the species to which it belonged. This mode of discri- 

 mination is peculiarly useful in the study of fossil fishes, as in 

 them the enamelled condition of the scales rendered them more 

 durable than even their bones; and it not unfrequently happens, 

 that all the scales of a fish are found in entire preservation, 

 while their bony skeleton has entirely disappeared ; this arises 

 from the enamel of the scales being less soluble than the calca- 

 reous substance of the bone. M. Agassiz divides fishes into the 

 following new Orders : 



ORDER I. PLACOIDIANS. 



Skin irregularly covered with plates of enamel, frequently of 

 considerable dimensions, and sometimes reduced to small points, 

 like shagreen on the skins of many sharks, and the tooth-like 

 tubercles on the skins of rays. This order embraces the whole 

 cartilaginous fishes of Cuvier, with the exception of the stur- 

 geon. See an example of the scales of this Order, pi. 65, figs. 

 89,90. 



ORDER II. GANOIDIANS. 



With angular scales, composed of horny or bony plates, cov- 

 ered with a thick plate of enamel. In this order he has in- 

 cluded the sturgeon and bony pike. There are upwards of 

 sixty genera, of which fifty are fossil. See example of scales, 

 pi. 65, figs. 87, 88. 



ORDER III. CtENOIDIANS. 



Scales jagged or pectinated like the teeth of a comb, or on 

 their posterior margin. They are formed of laminae of horn or 

 bone, but are destitute of enamel. The scales of the perch are 

 so constructed. See example of scales, pi. 65, figs. 91, 92. 



ORDER IV. CYCLODIANS. 



Scales smooth, and simple at their margin, and often ornamented 

 with various figures on the upper surface. These scales are 

 composed of laminae of horn or Done, but are destitute of ena- 

 mel. The scales of the salmon and herring illustrate this order. 

 See pi. 65, figs. 93, 94. 



Each of these orders contains both cartilaginous and bony 

 fishes; the representations of each prevailed in different pro- 

 portions during different epochs; only the two first existed 

 before the commencement of the cretaceous formations; the 

 third and fourth orders, which contain three-fourths of the 

 eight thousand known species of living fishes, appear, for the 

 first time, in the cretaceous strata, when all the preceding' fossil 

 genera of the two first orders had become extinct. 



The general result of the discovery and inquiry into these 

 important fossil remains, is, that those which are imbedded in 

 strata, of the greatest antiquity, differ more widely from exist- 

 ing genera and species than those of the most recent tertiary 

 deposits, mid afford a further confirmation, that all the great 

 changes, in the character of fossil fishes, have taken place si- 

 multaneously with the most important alterations in the other 

 classes of fossil animals, and in fossil vegetables, as well as in 

 the mineral condition of the strata. M. Agassiz has found that 

 fossil fishes, in the same formation, present greater variations 



greater locomotive powers of this higher class of animals. And 

 an important result has attended his discoveries, namely, that 

 the age and place of several formations, hitherto undetermined, 

 have been rendered clear, by a knowledge of the fishes imbed- 

 ded in them. 



We can only allude to a few of this numerous Class, 

 out a few which are imbedded in different formations 



S nrrf, or Lixard Fishei, of the family Ganoid These 

 must have been very voracious animals, and in the character of 

 their bones agreeing both with fishes and reptiles. Seventeen 

 genera of this family have been ascertained by Agassiz, only 

 two of which are to be found in a recent state; and these are the 

 Lcpisoteut,or bony pike of Lacepede; and Polyptenu, the former 

 inhabiting the Nile, and the latter the rivers of North America. 

 The teeth of fishes of this family, of a conical form, and of a 

 size larger than those of any crocodile, have been found in the 

 coal formations in the neighbourhood c,f Hclintmn;li ; these arn 

 considered to be of a new genus, which Agassi/, calls Megalich- 

 thys. The magnesian limestone furnishes us \viti> examples of 

 the smaller sauroid fishes, and very large hones are found in 

 the lias at Whitby and Lyme Regis ; and the genera abound 

 throughout the whole oolite formation, and almost disappear 

 in the cretaceous formations. They have not been found in the 

 tertiary formations. 



Fishes of the genus dmb/ypterui, a genus limited to the eany 

 periods of geological formations, and is found in the carbonifer- 

 ous strata at Staarbruk, in Lorraine, and also in Brazil, pi. G5. 

 fig 86. These animals seem to have been destined to feed on 

 soft and decayed seaweed, and tender animal substances; as the 

 teeth are numerous, very email, and set together in fasciculi, 

 like the hairs of a brush. 



SHARKS seem more universally diffused in a fossil state than 

 any other family. Insulated specimens of their teeth have been 

 found in every country. Agassiz has separated this great 

 family into three sub-families ; the oldest of which he calls Cci- 

 tracionts, which occupy every series of strata, from the transi- 

 tion to the beginning of the tertiary. There is otily one living 

 representative of this family in the Cestracion 1'bilippi of Port 

 Jackson. The second sub-family commences with the Muschel- 

 kalk, and probably with the coal formation, spreads over the 

 oolite series, and ends at the beginning of the chalk. The 

 Squaloids, or third sub-family, has its origin in the cretaceous 

 formation, and extends through the tertiary strata. Fi}.'. 10, pi. 

 65, is a tooth of an extinct species of shark, measuring four 

 inches and a half in length, and three and a half in width at the 

 base, which Lacepede considered belonged to an enormous 

 animal, not less than seventy feet in length. Fig. 18 represents 

 a tooth of a dog-fish, as given by Silla. The second division of 

 this family is the Hybodonts, fossils of which appear with the 

 coal formation, and prevail through the secondary strata under 

 the chalk ; the teeth of this sub-family present characters 

 intermediate between cestracion and ' squaloids. Fig. 14 is 

 another fossil tooth, resembling those of the Squalus Zygrna 

 in form. Fig. 17 is a longitudinally striated tooth, which wus 

 found in a moss with others, evidently belonging to the same 

 fish, at the Old Passage, Gloucestershire, by Mr Johnson of 

 Bristol, which last may be referred to a fish of this family. 



The fishes of the Muschelkalk consist of species Which arc 

 either peculiar to it, or are similar to those imbedded in the 

 oolite and lias. During the middle geological ages, fish of the 

 genus Microdon, and of the family Pycnodont3, or thick-toothed 

 fishes, of which there are five genera. Another important and 

 very abundant family, was the Lepidoids, which are remarkable 

 for the great thickness and beautiful enamel of their scales. 

 To this family belongs the genus Dapedittm, of which we have 

 given an example in the species Ptlitum, from Lyme Regis, 

 pi. 65, fig. 9. The scales of this genus, figs. 87 and 88, are 

 generally provided on the upper margin with a large hooked 

 process, not unlike that of a tile, which fits into a small pit, on 

 the lower margin of the scales placed next above it. M. 

 Agassiz has determined 200 fossil species with this sort of 

 armour. No living example exists of all the genera found in 

 the oolite series. 



In the CHALK FORMATION'S, there is a remarkable change in 

 the character of its fishes. This commences with the cretaceous 

 series. All the genera which prevailed in the older series 

 suddenly disappear, and are replaced by those of the new 

 Ctenoidean and Cydoidean orders. Nearly two-thirds of the 

 latter are now extinct ; but these are more nearly allied to 

 fishes of the tertiary series, than to those which had preceded 

 the formation of the chalk. When we compare the fishes of 

 the chalk with those of the elder tertiary series of Monte 

 Bolea, we do not find a single species, and only a few belong- 

 ing to the genera, that are common to both. 



No sooner do our investigations reach the TERTIARY FORMA- 

 TIONS, than a still more decided change presents itself. 'J'he.-e 

 belonging to the Eocene period ; more than a half of which are 

 now of extinct genera, and not one of which can be found an 

 existing species. The forms that now remain are only to be 

 met with in tropical regions. Agassiz has re-arranged these 

 fishes, and formed from them 77 genera, 38 of them extinct, 

 and of which there are 1<27 extinct species. Of living genera 

 there are 39, to which belong 81 fossil species, found at Monte 

 Bolea. Belonging to the extinct genera, tliere are 46 species 

 found at Monte Bolea. The fishes of the London clay, Sheppy, 

 as well as Monte Bolea and Mont Martre, belong to the first 

 period of the tertiary formations. Those fishes belonging to 

 Oeningen, which all naturalists have considered connected with 

 a very recent lacustrine deposit, have been referred by Aga-siz 

 to the second period of the tertiary series, and of a date cor- 

 responding with that of the Molasse of Switzerland. All of 

 these belong to living genera, and only one species is of an 

 extra European genus. 



The rays which belong to the fourth family of the order of 

 Placoidiaus, have not been found in strata older than the lias 

 and the Jura limestone, and abound in the tertiary formation. 



We have seen from the above rapid review of fossil fishes, 

 that with the dawn of sub-marine existence, commenced, and 



