The uppermost layers of this ferrugino-sandy mass are conformably covered by, and impregnated to the depth of several inches with, the calcareous matter of the bed D called losa: hence I at one time imagined that there was a gradual passage between them; but as all the species are recent in the bed D, whilst the most characteristic shells of the uppermost layers of E are the extinct Perna, Pecten, and Monoceros, I agree with M. d’Orbigny, that this view is erroneous, and that there is only a mineralogical passage between them, and no gradual transition in the nature of their organic remains. Besides the fourteen species enumerated from these two lower beds, M. d’Orbigny has described ten other species given to him from this locality; namely:— 1. Fusus Cleryanus, d’Orbigny “Voyage” Pal. 2. Fusus petitianus, d’Orbigny “Voyage” Pal. 3. Venus hanetiana, d’Orbigny “Voyage” Pal. 4. Venus incerta (?) d’Orbigny “Voyage” Pal. 5. Venus Cleryana, d’Orbigny “Voyage” Pal. 6. Venus petitiana, d’Orbigny “Voyage” Pal. 7. Venus Chilensis, d’Orbigny “Voyage” Pal. 8. Solecurtus hanetianus, d’Orbigny “Voyage” Pal. 9. Mactra auca, d’Orbigny “Voyage” Pal. 10. Oliva serena, d’Orbigny “Voyage” Pal. Of these twenty-four shells, all are extinct, except, according to Mr. Sowerby, the Artemis ponderosa, Mytilus Chiloensis, and probably the great Balanus. COQUIMBO TO COPIAPO. A few miles north of Coquimbo, I met with the ferruginous, balaniferous mass E with many silicified bones; I was informed that these silicified bones occur also at Tonguay, south of Coquimbo: their number is certainly remarkable, and they seem to take the place of the silicified wood, so common on the coast-formations of Southern Chile. In the valley of Chaneral, I again saw this same formation, capped with the recent calcareous beds. I here left the coast, and did not see any more of the tertiary formations, until descending to the sea at Copiapo: here in one place I found variously coloured layers of sand and soft sandstone, with seams of gypsum, and in another place, a comminuted shelly mass, with layers of rotten-stone and seams of gypsum, including many of the extinct gigantic oyster: beds with these oysters are said to occur at English Harbour, a few miles north of Copiapo. COAST OF PERU. With the exception of deposits containing recent shells and of quite insignificant dimensions, no tertiary formations have been observed on this coast, for a space of twenty-two degrees of latitude north of Copiapo, until coming to Payta, where there is said to be a considerable calcareous deposit: a few fossils have been described by M. d’Orbigny from this place, namely:—