When we take, instead of Great Britain, the whole explored geological field of the world, the result, so far as the argument is concerned, will be strengthened, not weakened. The formations of other lands are simply, with slight variations, a repetition of our own. The same genera of animals are everywhere prevalent. The specific types are likewise in many instances identical. The silurian organisms of Russia are so like those in our own island, that “no English geologist,” says Murchison, “acquainted with the organic contents of the Wenlock limestone, can view the Calymena Blumenbachii, C. macrophthalma, C. variolaria, and other Trilobites associated with the Leptœna depressa, L. euglypha, Terebratula reticularis, and many corals most familiar to him, without at once recognizing in the upper strata the distinct representative of that British formation.” Various other fossiliferous identities are farther alluded to, when it is added—“In taking leave of Scandinavia, we must specially advert to the close relations which exist between its lower and upper silurian groups, and those of Great Britain and distant parts of the world. Of 133 silurian fossils which we brought back or noted on the spot, at least eighty-four are British, and from twenty-five to twenty-seven are North American species. In this comparison the identity of the upper silurian groups of the Baltic and Great Britain is, indeed, most surprising; for, among seventy-four Scandinavian species, upward of sixty are common to the strata of this age in both countries, and of these, fifteen to sixteen species are also found in the upper silurian rocks of America.” The devonian fossils are equally striking in their resemblances and extensive geographical distribution. Similar representatives are detected, and still more abundantly, in the carboniferous formation—universal specific types of the fauna of the epoch. One remarkable instance has been stated—upon the authority of M. L. Von Buch—that the _Leptœna lata_, so typical of the silurian rocks of Britain, is specifically the same with the _Leptœna sarcinulata_, which is no less prevalent in the Russian carboniferous strata, and continued even throughout its uppermost members. Our field of review, therefore, contains a fair proportion of the various fossils of the world, specific and generic. The formations lying before us throughout our base-line, give a true indication of the state and conditions of life during the several epochs, while in number and variety of individual forms they are above the average.