Apart from the papers dealing with the extinct vertebrate faunas, the following are important works on the geology of Patagonia. For further literature, see the bibliography appended to Dr. Ortmann‘s Report. II. The Sedimentary Rocks. The latest classification of the Patagonian sediments is that by Mr. J. B. Hatcher, who conducted the Princeton University Expeditions. Previous to its appearance, M. Alcide Mercerat, of Buenos Aires, published a classification based on his observations in Southern Patagonia. Both are summarized here in tabular form:— During several manths' travelling in Patagonia I had opportunities of gaining some knowledge of the geology of the country; but, owing to the great distance traversed in the time, I found that it was impossible to study the stratigraphy satisfactorily, except in the neighbourhood of Santa Cruz, where a few weeks were spent. In that district the Patagonian and the Santa Cruz Beds are excellently exposed, as also is the ‘gravel-formation,’ which, in order to avoid any confusion, will be referred to hereafter as the Téhuelche Pebble-Bed. Fig. 1 (p. 162) represents a section of the Patagonian Beds at Entrance Point, at the mouth of the Rio Santa Cruz. The divisions mentioned by Darwin in ‘Geological Observations’ lie respectively between the 272-foot and 220-foot levels, the 220-foot and 159-foot levels, the 159-foot level and the talus-marks. These beds were also examined 18 miles up stream, on the estancia of Don Pedro Richmond, where they yield a rich invertebrate fauna. The section here does not present so varied a