68 Cincinnati Society of Natural History. 



two species of Fucoides that I know of from this terrane, 

 appear to belong to an almost entirely exotic genus, to the 

 genus Caulerpa of Lamouroux, that does not exist in our 

 seas, except one species, very different from the fossil species. 



4. Fucoides furcatus, recurvtis, diffortnis, cequalis and intri- 

 catiis are found in a formation that is represented in many 

 very remote places with nearlj- similar characters, but the 

 position of which is not yet well fixed by geologists, and 

 which my father presumed might belong, like those of the 

 Island of Aix, to the lower lignites of the chalk. 



Thus, Fucoides intricatiis is found near the chateau of 

 Malaspina, near Sarzana ; in the marls accompanying the 

 lignites quarried near Kaltenberg, to the north-east of 

 Vienna, in Austria; and the hill west of Genoa, betw^een St. 

 vStephan and St. Morizzio, near Oneille, without one being 

 able to establish the least difference between the Fucus forms 

 themselves, or in the rocks in which they are enclosed. 



Fucoides cEqualis is found at Vernasque, in the Appenines ; 

 to the south of Fiorenzola, in the Plaisantin; and at Bidache, 

 near Bayonne, in exactly similar marls. 



Fucoides furcatus is represented at \'ernasque ; in the 

 environs of Vienna, and near Sarzana. 



Finally, Fucoides recurtnis has been found thus far only at 

 Vernasque, and Fucoides difformis only at Bidache. 



But the perfect resemblance of the two other species, and 

 those of the rocks in which the}' are contained, seems to have 

 sufficiently established the analogy of these terranes. It is 

 curious to note that these various species seemingly belong to 

 one and the same section of this genus, and this renders it 

 more difficult to well define their limits. 



Having indicated the geological position in which these 

 fossils are found, I shall now proceed to describe the species 

 that I can refer to the genus Fucoides. 



FrcoiDp:s. 



Frond continuous, often membranaceous and spreading in 

 the same plane ; the two sides generally unequal ; nerves 

 more or less ill-defined, never regularly divided or anasta- 

 niosing. 



