Isolated crania and detached vertebræ are nearly all that remain of the Sheppey fossils, and the conclusions established from them by M. Agassiz, are as follows, throwing new and important light upon the two last great and approximating geological epochs. The English coasts, at present, are inhabited by one hundred and sixty-three species of fish, of which there are eighty-one genera, divided among six predominant families, while two or three are only occasionally domiciled. Sixty species belong to the order of Ctenoids, fifty to that of the Cycloids, and eleven to the Ganoids. The fossil distribution establishes the following results: of Ctenoids twelve species, eleven genera, and three families, of which the perch tribe is the most numerous; three genera of the Teuthiæ, a family essentially meridional, and occurring only in southern seas, a fact which shows a higher climatic condition of temperature than now exists in this latitude; thirty-two species of the Cycloid order, twenty-six genera, and eleven families—of these the cod and mackerel tribes are the most numerous. While no trace of the family Salmonidæ has been detected in the tertiary deposit, a family exclusively tropical, the Characidæ, is found to have had congeners of very considerable size in the more ancient epoch. The haddock, cod, and ling races are very abundant—a fact, says Agassiz, which proves that, notwithstanding the more meridional physiognomy of the Sheppey deposit as a whole, there is nevertheless already an approximation in the fish of this interesting locality toward the actual character of the ichthyological fauna of England. The living representatives of most of these fossils are, if anywhere, to be looked for in southern and tropical latitudes; for, notwithstanding of an approximation, there is not much of real identity of type between the existing and extinct races of the British seas. In fact, there are but four genera, _Megalops_, _Cybium_, _Tetrapterus_, and _Myripristis_, whose families are still known in the current epoch; and but very few species, from the rich prolific beds of Sheppey, have been as yet rendered into living forms.—The fishes most nearly related to the present inhabitants of warmer climes are those which are obtained from the fossil tertiary deposits of Monte Bolca in northern Italy, and in the little explored region of Mount Lebanon. Much remains to be done, therefore, before wider generalizations can be fully established. The knowledge already acquired in this department of ichthyology confirms every previous inference relating to periodic physical changes of the globe, and their convergency to the order and arrangements of nature which now prevail over the earth.