on the Fossils of the older Deposits in the Rhenish Provinces. 327 



Of the forty-seven species of the Devonian system the greater part belong to the 

 hmestones of Elbersreuth and the Fichtelgebirge, and they are less plentiful in the 

 beds of the same age on the banks of the Rhine, in the Eifel, Belgium, and the west 

 of England. The seven species which are common to the first two systems are 

 also obtained in the most distantly separated countries : such are 0. Ibex, Sow. (Sil. 

 Syst.), found in England, at Wissenbach and Gottland ; the 0. Ludense, id., of 

 England, Elbersreuth and Revel; the O.regularis, Blum., and 0. Calamiteus, Count 

 Miinster. The fifty-two Carboniferous species have been particularly observed in 

 Scotland, and in the mountain limestone of Ireland, Yorkshire and Belgium. They 

 are not common in the coeval deposits of the north of Russia. The 0. Unguis, 

 Phil., 0. Steinhaueri, Sow., and 0. Gesneri, Mart. , have been pointed out as occurring 

 at the most distant localities in Europe. Three species, the 0. cylindraceus, 0. la- 

 teralis, and 0. giganteus, are Devonian as well as Carboniferous ; and the 0. imbri- 

 catus, Wahl., with 0. cinctus. Sow., unite the three systems together. 



If the great development of the Orthoceratites in the ancient seas of our hemi- 

 sphere be considered, it will appear astonishing that only five or six species should 

 be known in North America, where the contemporaneous deposits are so much 

 more greatly extended ; but a sort of compensation is established between the two 

 sides of the Atlantic by means of other genera, as we shall presently show. 



The Cyrthoceratites are very scarce in the Silurian system, but they are exten- 

 sively developed in the Devonian, in which are reckoned twenty-one species, 

 from the south-west of England, the Eifel, and the banks of the Rhine. One 

 of these is noticed at the cascade of Montmorency in Canada. Of nine Carboni- 

 ferous species, eight are from the environs of Tournay, and the ninth, common 

 to this and the preceding system, is found in Devonshire and the north of Russia. 

 Of the Phragmoceratites, four belong to the Ludlow beds and two to the limestones 

 of the Eifel and Elbersreuth. Of ten species of Lituites, nine are Silurian, and 

 occur in England, Scandinavia, and Esthonia. 



We have just remarked upon the rarity of the true Orthoceratites in North 

 America, and the same may be observed relatively to these last genera : still this 

 great family is not the less fully represented ; only, instead of specific characters, 

 taken from the external shells, much more decided differences may be observed — 

 differences in accordance with the organization of the animals which occupied the 

 shell. If the species which have been made in Europe are more numerous, the 

 types of the genera or subgenera in America are more varied. Thus the Conotu- 

 bularicB of the state of Tennessee* have only two analogues in Europe, the 0. cras- 



* Troost, Org. Rem. Valley of the Mississippi, Trans. Geol. Soc. Pennsyl., vol. i. part 2. p. 248, 

 1835. 



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