The great bulk of the specimens being arranged in these three series, supplementary collections for facilitating the study of the distribution of animals and plants in space and in time would be advantageous. The first, constituting a geographical series, might show by illustrative examples the leading characteristics of the fauna and flora of each great region of the earth’s surface; the second, or palæontological series, would give examples of the fossil remains found most abundantly in each formation, arranged so far as may be in chronological order. [Sidenote: Geographical.] [Sidenote: Geological.] The only attempt hitherto made at exhibiting a geographical series in the Museum is the collection of terrestrial and fresh-water vertebrated animals of the British Isles, arranged in the pavilion at the west end of the bird gallery. It would be difficult in the present building to find room for other geographical collections, however interesting and instructive. With regard to palæontological collections, although the specimens in the Department of Geology, so called, are mainly arranged not geologically, or according to stratigraphical position, but according to their natural affinities, yet, in many cases, it has been found convenient to adopt a mixed arrangement, the specimens within each large natural group being classified according to the sequence in age of the strata in which they were buried. Such an arrangement, however, is only applicable to the fossils of a particular region, owing to the difficulties in accurately determining the correspondence in age of formations occurring in distant parts of the earth’s surface; hence a large and varied palæontological collection, such as that of the British Museum, is best arranged in the main upon a systematic or zoological and botanical basis. A limited series showing the more characteristic British rock-formations with their included fossil remains, placed in chronological sequence, is arranged in one of the galleries of the Geological Department. DESCRIPTION OF THE MUSEUM AND ITS CONTENTS. On entering the Museum, the visitor should bear in mind that the principal front faces the south, so that he will be looking due north, with the east on his right, and the west on his left hand. It must also not be forgotten that a museum in a state of active growth is continually receiving additions as well as undergoing changes in the arrangement of its contents, and since these often occur faster than new editions of the Guide can be produced, there may be variations in the positions of some of the specimens from those here given. THE CENTRAL HALL. [Sidenote: Statues and Cases in the Central Hall.]