64 Br. Wheelton Hind — Carboniferous Life-Zones, 



very distinct, imich more so than one would judge from tlie remarks 

 and descriptions of De Koninck. Both S. cinctiis and S. Tornacensis 

 are more transverse, and possess fewer but thicker ribs, than 

 S. Mosquensis. The construction of the dorsal mesial fold and 

 corresponding sinus in the ventral valve is diiferent in each species. 

 At present, therefore, I am unable to affirm the presence of 

 aS". Mosquensis in Great Britain. 



It is an important fact to note, in connection with the absence 

 of the Spirifer Mosquensis zone in Belgium, that Prodiictns cora and 

 P. giganteus, the typical shells of the first and third zones in Russia, 

 should occur together in Belgium, and that, according to the Belgian 

 geologists, the beds with Productus cora are inferior to those with 

 JP. giganteus. In the P. cora zone of Eussia the fauna, taken as 

 a whole, is remarkably dissimilar to any that occurs in Western 

 Europe, especially towards the upper portion, most of the species 

 being entirely different. 



The intimate study of De Koninck's later monographs cannot but 

 convince the reader that with that author the erection of species was 

 largely secondary to the knowledge of the horizons at which the 

 various specimens were obtained. Starting with the preconceived 

 notion that there were at least three distinct molluscan faunas in the 

 Carboniferous Limestone of Belgium, he seized on the smallest 

 differences in detail or growth as a reason to invent a new species, 

 especially if it had been gathered from a special horizon. He says 

 himself (Ann. Mus. Hist. Nat. Beige, ser. Pal., tom. vi, p. 4) : "Siaux 

 caracteres differentiels constates enti'e des specimens provenant 

 d'assises differents quelques faibles, qu'ils soient, vient s'ajouter une 

 Constance bien etablie, il me semble loisible d'admettre que ces 

 specimens appartiennent a des especes distinctes, et c'est ainsi que 

 je les considererai." A very large number of the species which 

 De Koninck states are confined to one or other of his three horizons 

 in Belgium, I have found together in the Carboniferous beds of 

 Great Britain and Ireland, and am inclined to think that many of 

 his species will be found to be merely synonyms. 



In the volumes on the Lamellibranchs of the Carboniferous Lime- 

 stone of Belgium, 461 species are described by De Koninck, not one 

 of which is said to occur except in one stage. The numbers are as 

 follows : — 



461 



The species of Brachiopoda also are supposed to have had the same 

 limited distribution, for not one of the 130 species described is 

 common to two stages ; and out of 499 species of Gasteropoda 

 described only one species, and that with a query, is supposed to be 

 present in two horizons. Thus De Koninck would have it that there 

 are three absolutely distinct faunas, which never intermingle or 



