ON THE FOSSIL FISH OF THE DEVONIAN SYSTEM. 83 



the test of the most severe criticism. It suffices, in fact, to look at the bril- 

 liant results obtained by Mr. Owen from the structure of the teeth, to bo 

 convinced that in future no palaeontologist will be able to avoid microscopical 

 researches, if he wishes to arrive at a profound knowledge of the beings of 

 which he has undertaken to reconstruct the forms and the organization, even 

 in its most minute particularities. If, however, such detailed researches are 

 indispensable to establish general results, which sooner or later become public 

 property, it is not less important that they be expressed in the most simple 

 and correct manner, to render them intelligible to the largest number. 



One of the first observations to make on the ichthyological fauna of the 

 old red sandstone is, that it is wholly peculiar to this formation ; its numerous 

 species differ alike from those of the Silurian system and from those of the 

 carboniferous strata ; the greater portion of the genera even of the Devo- 

 nian system are restricted to the duration of this geological system, and of 

 tnis number are those containing most species, such as the genera Pterich- 

 thys, Coccosteus, Cephalaspis, Osteolcpis, Dipterus, Glyptolepis, Platygna- 

 thus, Dendrodus, Diplacanthus, Cheiracanthus, and Cheirolepis. Among 

 the genera which have representatives in the Silurian rocks or in the car- 

 boniferous series, such as the genera Onchus, Ctenacanthus, Ctenoptychius, 

 Ptyc/t acanthus, Acanthodes, Diplopterus, and Holoplychius, I am not ac- 

 quainted with a single one of which the species are identical in these dif- 

 ferent formations ; but, on the contrary, each formation in which they are 

 represented has its peculiar ones. This result agrees admirably with those 

 winch I have already obtained for the other strata of the series of rocks of 

 which the crust of our globe is composed, as well in my researches on fos- 

 sil fishes as also in those on the fossil Echinodermata and Mollusca. And 

 if my conclusions with regard to this latter class of animals were frequently 

 not in harmony with those of the greater number of conchologists, I have 

 at least the satisfaction of finding at present M. d'Orbigny arrive at the same 

 results from the study of other families and of other formations than those I 

 examined. This difference in the results which I had obtained arises, with- 

 out doubt, from my having applied, in determining the fossil remains of the 

 Mollusca, the same principles of criticism which have always guided me in 

 the determination of the fossil Vertebrata. 



It is now a truth which I consider as proved, that the " ensemble " of or- 

 ganized beings was renewed not only in the interval of each of the great 

 geological divisions which we have agreed to term formations, but also at the 

 time of the deposition of each particular member of all the formations ; for 

 example, I think that I can prove that in the oolitic formation, at least 

 within the limits of the Swiss Jura, the organic contents of the lias, those of 

 the oolitic group properly so called, those of the Oxfordian group, and those 

 of the Portlandian group, as they occur in Switzerland, are as different from 

 each other as the fossils of the lias from those of the Keuper, or those of 

 the Portlandian beds from those of the Neocomian formation. I also be- 

 lieve very little in the genetic descent of living species from those of the va- 

 rious tertiary layers which have been regarded as identical, but which, in 

 my opinion, are specifically distinct. I cannot admit the idea of the trans- 

 formation of species from one formation to another. In advancing these 

 general notions, I do not wish to offer them as inductions drawn from the 

 study of any particular class of animals (of the fishes for instance), and ap- 

 plied to other classes, but as the results of direct observation of very con- 

 siderable collections of fossils of different formations, and belonging to dif- 

 ferent classes of animals, in the investigation of which I have been spe- 

 cially engaged for many years, in order to assure myself whether the con- 



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