Of these, the greater part yet discovered have been named by Agassiz, the highest authority as an ichthyologist in Europe or the world, and in whom the scarcely more celebrated Cuvier recognized a naturalist in every respect worthy to succeed him. The comparative amount of the labors of these two great men in fossil ichthyology, and the amazing acceleration which has taken place within the last few years in the progress of geological science, are illustrated together, and that very strikingly, by the following interesting fact--a fact derived directly from Agassiz himself, and which must be new to the great bulk of my readers. When Cuvier closed his researches in this department, he had named and described, for the guidance of the geologist, ninety-two distinct species of fossil fish; nor was it then known that the entire geological scale, from the Upper Tertiary to the Grauwacke inclusive, contained more. Agassiz commenced his labors; and, in a period of time little exceeding fourteen years, he has raised the number of species from ninety-two to sixteen hundred. And this number, great as it is, is receiving accessions almost every day. In his late visit to Scotland, he found eleven new species, and one new genus, in the collection of Lady Gumming of Altyre, all from the upper beds of that lower member of the Old Red Sandstone represented by the dark-colored schists and inferior sandstones of Caithness. He found forty-two new species more in a single collection in Ireland, furnished by the Mountain Limestone of Armagh.