The island of Quiriquina, in the Bay of Concepcion, is formed of various soft and often ferruginous sandstones, with bands of pebbles, and with the lower strata sometimes passing into a conglomerate resting on the underlying metamorphic schists. These beds include subordinate layers of greenish impure clay, soft micaceous and calcareous sandstones, and reddish friable earthy matter with white specks like decomposed crystals of feldspar; they include, also, hard concretions, fragments of shells, lignite, and silicified wood. In the upper part they pass into white, soft sediments and brecciolas, very like those described at Chiloe; as indeed is the whole formation. At Lirguen and other places on the eastern side of the bay, there are good sections of the lower sandstones, which are generally ferruginous, but which vary in character, and even pass into an argillaceous nature; they contain hard concretions, fragments of lignite, silicified wood, and pebbles (of the same rocks with the pebbles in the sandstones of Quiriquina), and they alternate with numerous, often very thin layers of imperfect coal, generally of little specific gravity. The main bed here is three feet thick; and only the coal of this one bed has a glossy fracture. Another irregular, curvilinear bed of brown, compact lignite, is remarkable for being included in a mass of coarse gravel. These imperfect coals, when placed in a heap, ignite spontaneously. The cliffs on this side of the bay, as well as on the island of Quiriquina, are capped with red friable earth, which, as stated in the Second Chapter, is of recent formation. The stratification in this neighbourhood is generally horizontal; but near Lirguen the beds dip N.W. at an angle of 23 degrees; near Concepcion they are also inclined: at the northern end of Quiriquina they have been tilted at an angle of 30 degrees, and at the southern end at angles varying from 15 degrees to 40 degrees: these dislocations must have taken place under the sea. A collection of shells, from the island of Quiriquina, has been described by M. d’Orbigny: they are all extinct, and from their generic character, M. d’Orbigny inferred that they were of tertiary origin: they consist of:— 1. Scalaria Chilensis, d’Orbigny, “Voyage, Part Pal.” 2. Natica Araucana, d’Orbigny, “Voyage, Part Pal.” 3. Natica australis, d’Orbigny, “Voyage, Part Pal.” 4. Fusus difficilis, d’Orbigny, “Voyage, Part Pal.” 5. Pyrula longirostra, d’Orbigny, “Voyage, Part Pal.” 6. Pleurotoma Araucana, d’Orbigny, “Voyage, Part Pal.” 7. Cardium auca, d’Orbigny, “Voyage, Part Pal.” 8. Cardium acuticostatum, d’Orbigny, “Voyage, Part Pal.” 9. Venus auca, d’Orbigny, “Voyage, Part Pal.” 10. Mactra cecileana, d’Orbigny, “Voyage, Part Pal.” 11. Mactra Araucana, d’Orbigny, “Voyage, Part Pal.” 12. Arca Araucana, d’Orbigny, “Voyage, Part Pal.” 13. Nucula Largillierti, d’Orbigny, “Voyage, Part Pal.” 14. Trigonia Hanetiana, d’Orbigny, “Voyage, Part Pal.”