stalactiform, and contains some sand, earthy matter, and recent shells. It
lies on, and sends wedge-like veins into, a much more friable, calcareous,
tuff-like variety; and both rest on a mass about twenty feet in thickness,
formed of fragments of recent shells, with a few whole ones, and with small
pebbles firmly cemented together. (In many respects this upper hard, and
the underlying more friable, varieties, resemble the great superficial beds
at King George's Sound in Australia, which I have described in my
"Geological Observations on Volcanic Islands." There could be little doubt
that the upper layers there have been hardened by the action of rain on the
friable, calcareous matter, and that the whole mass has originated in the
decay of minutely comminuted sea-shells and corals.) This latter rock is
called by the inhabitants losa, and is used for building: in many parts it
is divided into strata, which dip at an angle of ten degrees seaward, and
appear as if they had originally been heaped in successive layers (as may
be seen on coral-reefs) on a steep beach. This stone is remarkable from
being in parts entirely formed of empty, pellucid capsules or cells of
calcareous matter, of the size of small seeds: a series of specimens
unequivocally showed that all these capsules once contained minute rounded
fragments of shells which have since been gradually dissolved by water
percolating through the mass. (I have incidentally described this rock in
the above work on Volcanic Islands.)

The shells embedded in the calcareous beds forming the surface of this
fringe-like plain, at the height of from 200 to 250 feet above the sea,
consist of:--

1. Venus opaca.
2. Mulinia Byronensis.
3. Pecten purpuratus.
4. Mesodesma donaciforme.