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-mal having been petrified : and a careful examination of this part allows 

 me to suppose that it is, in fact, either the Cornea or the Membrana nic- 

 titans, which has been thus preserved. I have been led to this supposition, 

 by discovering, by means of a lens, that in one specimen this part retains 

 an uncommonly smooth and polished surface, whilst, in another, it has 

 such a rugous appearance, as might be expected to be found in the mem- 

 brand ?iictita?is, on being exposed to the action of moisture after death. 



In some of these specimens, the branchial operculum, or covering of 

 the gills, is found in very tolerable preservation ; in others, the bony rays 

 of the fins are preserved ; and in most, where it is possible to remove the 

 adherent matrix, which is rarely the case, the bones of the head may be 

 displayed, in situ, and very interesting fossils thereby obtained. 



The jaws of the spinous fishes are also sometimes found in a very tole- 

 rable state of preservation ; being sometimes closed, and other times 

 very widely separated. In the British Museum is an uncommonly beau- 

 tiful specimen of the skin of the under lip of a fish in a mineralized state, 

 and in perfect preservation. This is the only fossil of the kind that I 

 have seen; nor can its rarity be wondered at, when it is considered, 

 that the proneness to decomposition, in this part, can hardly be expected 

 to give time for the impregnation necessary for its mineralization. 



The teeth of fish are, from their nature and structure, among the best 

 preserved and most numerous fossil remains of these animals. From the 

 number in which they exist, they particularly engaged the attention of 

 the early oryctologists, who distinguished them by names chiefly derived 

 from their forms. Hence we find them spoken of by the names of 

 Glossopetra, Plectronites, Rostrago, Falcatula, &c. Glossopetra was, however, 

 employed as the general term, expressive of a tongue converted into 

 stone : and, from certain differences in their size and forms, these were 

 supposed to have been the tongues of birds, serpents, &c. Gesner, Keis- 

 kius, Lang, and others, regarded them as sports of nature ; but Steno 

 and Fabius Columna at once asserted their animal origin, and pointed 

 out the animal to which they conceived they had belonged. 



