on the Fossils of the older Deposits in the Rhenish Provinces. 321 



banks of the river Volkof and in the government of Pskof ; it is also found 

 near the source of the Vitchedga, not far from the northern Ural. Those which 

 belong both to the Silurian and Devonian systems are found over a much more 

 considerable space; thus the T. Wilsoni, Sow., of England, is to be met with 

 also in Belgium, in Russia, in the island of Gottland, and in the states of Ohio 

 and Tennessee. The T.prisca and T. aspera, Schlot., are found in England, in the 

 north of France, in Belgium, in the Eifel, upon the banks of the Rhine, in Scan- 

 dinavia and the islands of the Baltic, also in Livonia, Esthonia, Ingria, the Uralian 

 chain, on the banks of the Thracian Bosphorus, near Smeinogorsk on the north side 

 of the Altai ; in America in the states of Tennessee, Ohio and Pennsylvania ; and, 

 finally, in the slaty clays of Moscow (New York) and on the banks of Lake Erie. 



The superior or Carboniferous system in Ireland, Yorkshire, Derbyshire and the 

 west of England, encloses a vast number of Terebratults , as well as the mountain 

 limestone of Hainault and of the provinces of Li^ge and Namur. They are not 

 so numerous in the carboniferous beds of the north and south of Russia. The 

 species peculiar to this system are not in general extensively distributed ; those 

 which are common to it and to the middle system have, on the contrary, been 

 collected very far apart ; thus the Terebratula hastata (Sow.), from Ireland, England, 

 and Belgium, has been found in Russia and as far as the Altai chain ; the T. acu- 

 minata, Sow., is common to both systems in England and in Belgium ; and lastly, 

 the T. Pleurodon, PhilL, occurs not only throughout Western Europe, but also in 

 Silesia, Livonia, and the Valdai near Smeinogorsk in Asia. It is not certain that 

 any species traverses the entire series of Palaeozoic rocks. 



If it were sought to establish any general difference of character in the Tere- 

 hratulfB of the three systems, it might perhaps appear that the striated or very 

 finely plicated species with sharp folds prevail in the Silurian \ that in the 

 Devonian these characters have a tendency to become less strongly marked, and 

 that the species with cross stria? and with a rugose surface, in consequence of the 

 decussation of these strise by longitudinal folds, become more abundant; and, 

 lastly, that the Carboniferous species have their folds larger and less numerous, 

 and that the shells are more frequently smooth and even, and that, like the Pro- 

 ducti and Spiriferi, they attain dimensions much more considerable. 



The genus Ungulites of Pander {Obolus, Eichw.) is known to be plentiful in some 

 Lower Silurian grits in the neighbourhood of St. Petersburg, but it does not extend 

 to the west of Revel. Two Crania are mentioned in the Eifel, and one species is 

 not rare in the Silurian beds of the neighbourhood of St. Petersburg and along the 

 shores of the Baltic in Esthonia. The Lingulcs and Orhiculoe, often but indistinctly 

 characterized, have been found in the several systems, but no species appears to 

 pass from one to another. Lastly, the Calceola sandalina, Lam., which fairly pecu- 



