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the eye of the animal 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 nictitans, 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 membrana nictitans , 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 BritishMuseum 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, See. 
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, See. Gesner, Reiskius, Lang, and others, regarded 
them as sports of nature ; but Steno and Fabius Columna at once 
