II. THE ORGANIC REMAINS of the tertiary deposits, if they possess not so much of antiquity as those which have already passed in review, are all the more interesting and worthy of attention, as they admit of a closer comparison with the established order of things, and the laws now regulating the distribution of animal and vegetable life. The locality most fertile in the organic remains of this period is the small island of Sheppey, situated near the mouth of the Thames, which is not more welcomely descried by the home-bound mariner as a Pharos of light and safety from the howling waste of waters, than it has proved to the palæontologist a repository and beacon-light for determining the most recondite mysteries connected with almost every living thing, in sea or land, during the Eocene age. It consists entirely of the London clay deposit, of an average thickness of five hundred feet, and displaying in the cliffs vertical faces two hundred feet high. The fossils in both localities are almost identical; in the isle of Sheppey they are more abundant, as well as accessible; and, in consequence, they have been more minutely and generally described. 1. The shells are very abundant. A few genera have survived the changes and disturbances succeeding the upheaval of the chalk, and a single species of Gasteropodes (Actæon elongatus), is common to both formations. The Belemnites and Ammonites, swarming in the seas of the secondary period, are now entirely withdrawn. The Nautilus is but sparingly represented. The new genus Cerithium is introduced, a long, tapering, spiral-formed shell, and apparently of strong predaceous habits. Lobsters resembling existing species are very abundant. The Nummulites, of which entire rocks were formed during the secondary age, still survive. And, as an index to the state of temperature, it requires to be mentioned, that many species, now found only in tropical seas, are mixed with the testaceous fossils of these localities.