DE VERNEUIL AND d'aRCHIAC ON RUSSIAN PALEOZOIC FOSSILS. 109 



several times observed in the carboniferous limestone ; and, accord- 

 ing to M. Eichwald, this shell is common to the Devonian and car- 

 boniferous systems in Russia as it is in England. According to the 

 same authority, species oi Natica are also not uncommon in Russia, 

 chiefly in the Silurian beds of Esthonia, but we have only met with 

 two species (both carboniferous); one of them, N. Marice, new, and 

 the other, N. Omaliaria, a Belgian shell. It is very doubtful whe- 

 ther any true Buccinum is met with in beds of the palaeozoic age, 

 and the shells which have been so named, but which have a mouth 

 very differently formed, have been properly separated by Mr. Phil- 

 lips under the name Macrocheilus. Amongst these are B. acutum 

 and B. imbricatum, which we have observed in the carboniferous 

 limestone of the Ural. Those mentioned by M. Fischer consist of 

 indeterminable casts. 



The Bellerophons, so widely distributed throughout the long se- 

 ries of deposits formed during the three older divisions of the palaeo- 

 zoic period, do not extend into the uppermost group, nor are they 

 met with in any newer beds, and their type, now entirely lost, is so 

 far removed from any existing organic form, that even the best 

 zoologists are at a loss to what place amongst animals they should 

 be referred. The whole number of species known, including both 

 Europe and America, is upwards of fifty, and increases from below 

 upwards, commencing with the Silurian rocks and terminating with 

 the carboniferous — a fact which renders the total extinction of the 

 group after the coal-measures the more striking. The old rocks of 

 Russia, following the general law of the distribution of these beings 

 during the palaeozoic period, present a tolerably large number of 

 Bellerophons, of which about eight or ten species have come under 

 our own observation ; and twelve others are quoted by various au- 

 thors, several of them however only established on the evidence of 

 casts somewhat widely spread in the carboniferous limestone. The 

 species carefully determined are B. megalostoma and B. ingricus of 

 the Silurian system, B. hiulcus and B. decussatus of the carbonife- 

 rous limestone of the Ural, and B. Ouralicusof the Silurian rocks of 

 the same mountain-chain. We have also recognised in situ frag- 

 ments of B. bilobatus, B. globatus and B. striaius. None of the 

 Russian species pass from one system into another, and we are in- 

 clined to suspect that in other parts of Europe where this law does 

 not appear to hold, and where some species, such as B. urii, belong 

 to several systems, that the number of these apparently common 

 species will diminish as the subject is more carefully studied. 



Pteropoda. — The Conularia^ a genus which two of the authors 

 (MM. de Verneuil and d'Archiac) have referred to the Pteropoda, 

 is rarely represented in Russia. We know at present only of the 

 small species, C. Buchii of St. Petersburg and C. Soiverbii of Ka- 

 menetz-Podolsk, which we have also met with in the neighbourhood 

 of Christiania. 



Cephalopoda. — In commencing the study of these shells, and ob- 

 serving their development during the period we are considering, we 

 cannot but take notice of the fact, tliat from the earliest iutroduc- 



