5. Turritella cingulata.
6. Monoceros costatum.
7. Concholepas Peruviana.
8. Trochus (common Valparaiso species).
9. Calyptraea Byronensis.

Although these species are all recent, and are all found in the
neighbouring sea, yet I was particularly struck with the difference in the
proportional numbers of the several species, and of those now cast up on
the present beach. I found only one specimen of the Concholepas, and the
Pecten was very rare, though both these shells are now the commonest kinds,
with the exception, perhaps, of the Calyptraea radians, of which I did not
find one in the calcareous beds. I will not pretend to determine how far
this difference in the proportional numbers depends on the age of the
deposit, and how far on the difference in nature between the present sandy
beaches and the calcareous bottom, on which the embedded shells must have
lived.

(DIAGRAM 8.--SECTION OF PLAIN OF COQUIMBO.

Section through Plain B-B and Ravine A.

Surface of plain 252 feet above sea.

A. Stratified sand, with recent shells in same proportions as on the beach,
half filling up a ravine.

B. Surface of plain, with scattered shells in nearly same proportions as on
the beach.