"The genus _Credneria_, containing dicotyledonous leaves, with a very peculiar nervation, but the affinities of which are doubtful, is likewise one of the characteristic forms of this epoch, in a pretty considerable number of localities. With regard to the species of dicotyledonous leaves, referred to determined families, I may remark that these supposed relations, founded on very imperfect specimens, and very few in number, are still very uncertain, and incapable of furnishing a basis for comparison with the other Floras, nor any certain conclusion. "_3d_, _Fucoidian Epoch_.--This epoch, which seems to me to form the most natural limit between the Cretaceous and Tertiary periods, is characterised by those deposits, so rich in Algæ, of a very peculiar form, that they have been called the sandstones or macignos à fucoïdes, or the flysch of Switzerland,--a formation very widely spread, especially in southern Europe, from the Pyrenees, as far as the vicinity of Vienna, and even to the Crimea. "I have not hitherto found land plants mingled with these marine species. I do not believe that fossil woods have been met with. "Almost all these Algæ appear to belong to the same group, the genus _Chondrites_; and although the species are pretty numerous, they pass from one to another by almost insensible shades. The Algæ of the neighbourhood of Vienna, placed in the genus _Munsteria_, are very ill characterised, and perhaps are not congenerous with those of the jurassic limestone of Solenhofen; but they appear to me to have been found in the same formation, designated by the name of gray calcareous slate, of the sandstone of Vienna, as the Chondrites of the same country." The Flora of the fucoidean sandstone is constituted by twelve species of Algæ (_Chondrites_ and _Munsteria_.) "What is remarkable in this series of species is, that they have nothing in common, either with the Algæ of the Subcretaceous epoch, or with those of the Eocene epoch, and particularly of Monte-Bolca, with which this Flora should be almost cotemporary, according to many geologists. The identity of these species of Algæ is likewise remarkable in all the localities, however distant from each other--localities so numerous, in regard to the greater number of these species, that I have been unable to enumerate them. "The Chondrites targionii, or perhaps a distinct species, but very nearly related, is the only one presented in another formation, in the greensand and gault of the Isle of Wight, in England, according to M. Fitton; and in this same formation, in the department of the Oise, according to M. Graves. "M. Kurr has likewise described and figured, under the name of _Chondrites bollensis_, a fucus of the Lias--the very varied forms of which are almost identical with the Chondrites targionii, æqualis, and difformis.