IX. 
GEOLOGICAL RELATIONS 
Under this head we propose to make only a few re- 
marks on the geological conditions in which such of 
the existing species as are foimd also in a fossil state 
occur, and to draw, from the few facts collected, such 
inferences as to their former condition on the earth's 
surface in the regions where they occur, as these facts 
may seem to warrant. The conclusions which depend 
upon the situation in which fossil terrestrial shells are 
found, are however, much less worthy of confidence 
than those derived from the marine fossils. The lafr 
ter may reasonably he supposed to have lived and died 
in the localities which they now occupy, while the for- 
mer have only been preserved by being removed from 
their original positions, and subjected to conditions en- 
tirely different from those under which they existed 
during life. The substance of all land-shells possesses 
so little solidity, and theh- texture is so frail, that when 
they are deprived of the protection that the animal 
itself affords them, the operation of the elements soon 
