Beneath the upper and central green circle, the wild valleys are
quite desolate and untenanted. Here, to the geologist, there were
scenes of high interest, showing successive changes and complicated
disturbances. According to my views, St. Helena has existed as an
island from a very remote epoch: some obscure proofs, however, of
the elevation of the land are still extant. I believe that the
central and highest peaks form parts of the rim of a great crater,
the southern half of which has been entirely removed by the waves
of the sea: there is, moreover, an external wall of black basaltic
rocks, like the coast-mountains of Mauritius, which are older than
the central volcanic streams. On the higher parts of the island
considerable numbers of a shell, long thought to be a marine
species, occur imbedded in the soil. It proves to be a Cochlogena,
or land-shell of a very peculiar form; with it I found six other
kinds; and in another spot an eighth species. (21/2. It deserves
notice that all the many specimens of this shell found by me in one
spot differ as a marked variety from another set of specimens
procured from a different spot.) It is remarkable that none of them
are now found living.
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