2. Olivancillaria auricularia, d'Orbigny.

3. Venus flexuosa, Lam.

4. Cytheraea (imperfect).

5. Mactra Isabellei, d'Orbigny.

6. Ostrea pulchella, d'Orbigny.

Besides these, Sir W. Parish procured ("Buenos Ayres" etc. by Sir W. Parish
page 168.) (as named by Mr. G.B. Sowerby) the following shells:--

7. Voluta colocynthis.

8. Voluta angulata.

9. Buccinum (not spec.?).

All these species (with, perhaps, the exception of the last) are recent,
and live on the South American coast. These shell-beds extend from one
league to six leagues from the Plata, and must lie many feet above its
level. I heard, also, of beds of shells on the Somborombon, and on the Rio
Salado, at which latter place, as M. d'Orbigny informs me, the Mactra
Isabellei and Venus sinuosa are found.

During the elevation of the Provinces of La Plata, the waters of the
ancient estuary have but little affected (with the exception of the sand-
hills on the banks of the Parana and Uruguay) the outline of the land. M.