C. Upper calcareous bed, and D. Lower calcareous sandy bed (Losa), both
with recent shells, but not in same proportions as on the beach.

E. Upper ferrugino-sandy old tertiary stratum, and F. Lower old tertiary
stratum, both with all, or nearly all, extinct shells.)

On the bare surface of the calcareous plain, or in a thin covering of sand,
there were lying, at a height from 200 to 252 feet, many recent shells,
which had a much fresher appearance than the embedded ones: fragments of
the Concholepas, and of the common Mytilus, still retaining a tinge of its
colour, were numerous, and altogether there was manifestly a closer
approach in proportional numbers to those now lying on the beach. In a mass
of stratified, slightly agglutinated sand, which in some places covers up
the lower half of the seaward escarpment of the plain, the included shells
appeared to be in exactly the same proportional numbers with those on the
beach. On one side of a steep-sided ravine, cutting through the plain
behind Herradura Bay, I observed a narrow strip of stratified sand,
containing similar shells in similar proportional numbers; a section of the
ravine is represented in Diagram 8, which serves also to show the general
composition of the plain. I mention this case of the ravine chiefly because
without the evidence of the marine shells in the sand, any one would have
supposed that it had been hollowed out by simple alluvial action.

The escarpment of the fringe-like plain, which stretches for eleven miles
along the coast, is in some parts fronted by two or three narrow, step-
formed terraces, one of which at Herradura Bay expands into a small plain.
Its surface was there formed of gravel, cemented together by calcareous
matter; and out of it I extracted the following recent shells, which are in
a more perfect condition than those from the upper plain:--