as possessing “the advantage, in point of likelihood,” over those of the geologists his antagonists: his ally the Dean of York goes greatly further, and stands up as stoutly for the transmutation of species as Lamarck himself. Descanting, in his _New System of Geology_, on the various forms of trilobites, ammonites, belemnites, &c. Dean Cockburn says,— “These creatures appear to have possessed the power of secreting from the stone beneath them a limy covering for their backs, and perhaps, fed partly on the same solid material. Supposing, now that the first trilobites were destroyed by the Llandeilo Slates, some spawn of these creatures would arise above these flags, and, after a time, would be warmed into existence. These _molluscs_,[!!] then, having a better material from which to extract their food and covering, would probably expand in a slightly different form, and with a more extensive mantle than what belonged to the parent species. The same would be still more the case with a new generation, fed upon a new deposit from some deeper volcano, such as the Caradoc or Wenlock Limestone, in which lime more and more predominates. Now, if any one will examine the various prints of trilobites in Sir R. Murchison’s valuable work, he will find but very trifling differences in any of them,[!!] and those differences only in the stony covering of their backs. I knew two brothers once much alike: the one became a curate with a large family; the other a London alderman. If the skins of these two pachydermata had been preserved in a fossil state, there would have been less resemblance between them than between an _Asaphus tyrannus_ and an _Asaphus caudatus_.... A careful and laborious investigation has discovered, as in the trilobites, a difference in the ammonites of different strata; but such differences, as in the former case, exist only in the form of the external shell, and may be explained in the same manner.[!!] ... As to the scaphites, baculites, belemnites, and all the other _ites_ which learned ingenuity has so named, you find them in various strata the same in all important particulars, but also differing slightly in their outward coverings, as might be expected from the different circumstances in which each variety was placed.[!!] The sheep in the warm valleys of Andalusia have a fine covering like to hair; but remove them to a northern climate, and in a few generations the back is covered with shaggy wool. The animal is the same,—the covering only is changed.... The learned have classed those shells under the names of terebratula, orthis, atrypa, pecten, &c. They are all much alike.[!!!] It requires an experienced eye to distinguish them one from another: what little differences have been pointed out may readily be ascribed, as before, to difference of situation.”[!!!]