1. Gastridium cepa, G.B. Sowerby. 2. Monoceros, fragments of, considered by M. d’Orbigny as a new species. 3. Voluta alta, G.B. Sowerby (considered by M. d’Orbigny as distinct from the V. alta of Santa Cruz). 4. Voluta triplicata, G.B. Sowerby. 5. Oliva dimidiata, G.B. Sowerby. 6. Pleurotoma discors, G.B. Sowerby. 7. Pleurotoma turbinelloides, G.B. Sowerby. 8. Fusus subreflexus, G.B. Sowerby. 9. Fusus pyruliformis, G.B. Sowerby. 10. Fusus, allied to F. regularis (considered by M. d’Orbigny as a distinct species). 11. Turritella suturalis, G.B. Sowerby. 12. Turritella Patagonica, G.B. Sowerby (fragments of). 13. Trochus laevis, G.B. Sowerby. 14. Trochus collaris, G.B. Sowerby (considered by M. d’Orbigny as the young of the T. laevis). 15. Cassis monilifer, G.B. Sowerby. 16. Pyrula distans, G.B. Sowerby. 17. Triton verruculosus, G.B. Sowerby. 18. Sigaretus subglobosus, G.B. Sowerby. 19. Natica solida, G.B. Sowerby. (It is doubtful whether the Natica solida of S. Cruz is the same species with this.) 20. Terebra undulifera, G.B. Sowerby. 21. Terebra costellata, G.B. Sowerby. 22. Bulla (fragments of). 23. Dentalium giganteum, do. 24. Dentalium sulcosum, do. 25. Corbis (?) laevigata, do. 26. Cardium multiradiatum, do. 27. Venus meridionalis, do. 28. Pectunculus dispar, (?) Desh. (considered by M. d’Orbigny as a distinct species). 29, 30. Cytheraea and Mactra, fragments of (considered by M. d’Orbigny as new species). 31. Pecten, fragments of. COQUIMBO. (FIGURE 21. SECTION OF THE TERTIARY FORMATION AT COQUIMBO. From Level of Sea to Surface of plain, 252 feet above sea, through levels F, E, D and C: F.—Lower sandstone, with concretions and silicified bones, with fossil shells, all, or nearly all, extinct. E.—Upper ferruginous sandstone, with numerous Balani, with fossil shells, all, or nearly all, extinct. C and D.—Calcareous beds with recent shells. A.—Stratified sand in a ravine, also with recent shells.) For more than two hundred miles northward of Navidad, the coast consists of plutonic and metamorphic rocks, with the exception of some quite insignificant superficial beds of recent origin. At Tonguay, twenty-five miles south of Coquimbo, tertiary beds recommence. I have already minutely described in the Second Chapter, the step-formed plains of Coquimbo, and the upper calcareous beds (from twenty to thirty feet in thickness) containing shells of recent species, but in different proportions from those on the beach. There remains to be described only the underlying ancient tertiary beds, represented in Figure 21 by the letters F and E:—