DE VERNEUIL AND d'aRCHIAC ON RUSSIAN PALEOZOIC FOSSILS. 105 



sia, would hardly deserve mention, were it not that one of them, 

 C. sarcinulata, is as common in the carboniferous limestone of Rus- 

 sia as it is elsewhere in the Silurian rocks. 



The Productus, with which one species of Chonetes ( C. sarcinu- 

 latd) has been long confounded, offers in Russia a variety of forms 

 corresponding to the vast extension in that country of the carboni- 

 ferous limestone, in which this genus is chiefly developed. Both 

 before and after the carboniferous period, indeed, it seems to have 

 existed only in an imperfect and languid manner, presenting but 

 three species in each of the two neighbouring systems, Devonian 

 and Permian. The species in the older deposit are not striated, but 

 are covered with spines, and greatly resemble one another, being in 

 fact conformable to the single type of the genus occurring at this 

 period elsewhere in Europe and in America. The carboniferous 

 system in Russia contains twenty-two species, of which two only are 

 new. The most common of the number are the following: P.stria^ 

 tusy P, giganteuSy P. lobatus, P. punctatus^ P. scabriculus and P. 

 semireticulatus (antiquatus). The latter of these species abounds 

 everywhere and deserves special remark, for distributed, as it is, as 

 widely in Russia as elsewhere, and extending from Archangel and 

 Spitzbergen as far as Cabrales in Spain, it serves better than any 

 other to prove how different the physical and climatal conditions of 

 the earth's surface must have been at the time it flourished from 

 those which now obtain. 



Those Brachiopoda which have no true hinges appear to have 

 been represented formerly as at present by a much smaller number 

 of species than the group just alluded to. The genus Obolus {Un- 

 gulites)^ whose remains are so widely spread in the neighbourhood 

 of St. Petersburg and on the coasts of Esthonia, seems to have been 

 replaced both in England and in America by small species of Lin- 

 gular to which, from its subcoriaceous shell, it has considerable re- 

 semblance. The only animals hitherto found associated with these 

 early inhabitants of our planet are two small Orbiculas, which by the 

 form of their ventral valve are quite distinct from existing species, 

 and resemble closely an American species, O. Lodensis, The Lin- 

 gulas appear in Russia a little later, and in the chloritic limestones 

 which rest on the sandstone ; but there are two or three species, one 

 of which, discovered by M. Eichwald in the isle of Dago and near 

 Hapsal, is remarkable for its large size. These shells are still un- 

 known in the carboniferous system of Russia, and we have only found 

 one small species in the Devonian sandstones of Dorpat, and one 

 other still smaller in the Permian limestones of Cleveline between 

 Sergiesk and Bougoulma. With regard to Crania, the genus is 

 generally very rare in the palaeozoic rocks, and for this reason the 

 species found near St. Petersburg deserves mention. Lastly, to con- 

 clude the review of this group of Brachiopoda, we may mention the 

 genus Siphonolreta, remarkable for the position of the apicial open- 

 ing, and by the tube which proceeds from it. It has only hitherto 

 been found in the environs of St. Petersburg. 



Acephala* — If in the Brachiopoda the large number of the spe- 



