have successively occupied the surface of the Earth. 353 



3. Fucoidean Epoch. 



This epoch, which seems to me to form the most natural limit 

 between the cretaceous and tertiary periods, is characterized by 

 those deposits, so rich in Algae of a very special form, which have 

 been called fucoid sands or macignos, or the flysch of Switzerland, 

 a formation widely distributed, especially in Southern Europe, 

 from the Pyrenees to the environs of Vienna, and even as far as 

 the Crimea. 



At present no terrestrial plants have ever been found inter- 

 mixed with these marine plants. I do not think that even fossil 

 woods have been met with. 



Almost all these Algae appear to belong to the same group, to 

 the genus Chondrites, and although the species are tolerably 

 numerous, they pass into one another by almost insensible 

 shades. The Algse of the environs of Vienna, placed in the ge- 

 nus Mumteina, are very badly characterized, and perhaps are not 

 congeneric with those of the Jurassic limestone of Solenhofen ; 

 but they seem to me to have been found in the same formation, 

 designated by the name of the gray calcareous schist, of the sand 

 of Vienna, as the Chondrites of the same country. 



Chondrites recurvus, Brong. 



Huotii, Brong. 



affinis, Sternb. (Sphaerococ- 



cites.) 

 inclinatus, Sternb. (Sphaero- 



coccites.) 

 Munsteria Hassii, Sternb. 



flagellaris, Sternb. 



geniculata, Sternb. 



Flora of the Epoch of the 

 Fucoid Sand. 



Alg^. 



Chondrites intricatus, Brong. 



aequahs, Brong. 



difformis, Brong. 



Targionii, Brong. 



furcatus, Brong. 



The remarkable points about this series of species are, that 

 they have nothing in common either with the Algae of the subcre- 

 taceous epoch, or with those of the eocene epoch, especially of 

 Monte Bolca, with which this flora would be almost contempo- 

 raneous, according to many geologists ; and, again, the identity 

 of these species of Algae in so many localities situated at great 

 distances, localities so numerous for most of these species that I 

 have not been able to cite them. 



Chondrites Targionii, or perhaps a distinct, but very nearly ap- 

 proaching species, is the only one presented in another formation, 

 in the greensand and gault of the Isle of Wight, in England, ac- 

 cording to Dr. Fitton, and in the same formation in the depart- 

 ment of the Oise, according to Mr. Graves. 



M. Kurr has also described and figured under the name of 

 Chondrites BoUensis, a Fucus of the lias, the very varied forms of 

 which are almost identical with Chondrites Targionii, eequalis and 

 diffm-mis. 



