Limestones of South Devon. 733 



the divisions of the Silurian system in England, he is of opinion are good 

 for this country, but that differences more or less marked ought to occur in 

 other countries, and that such actually exist in Belgium. 



In M. Dumont's work, justly valued for unravelling the structure of an in- 

 tricate country, for its minute mineralogical and local delails, and for its ex- 

 cellent map, lists of fossils are appended to each system. On an inspection 

 of them, it was impossible not to be struck with the great proportionate num- 

 ber of mountain-limestone or Devonshire fossils, and the few solely Silurian. 

 In briefly remarking on their contents, I will take the lists in a descending 

 order, for the sake of departing from the systeme calcareux superieur, which 

 is clearly proved to belong to the carboniferous series by containing 38 well- 

 known English mountain-limestone species. 



Of the ten shells specifically determined, from the systhne quartzo- schist eux 

 superieur, namely, Spiri/era atlenuata, S. bisulcata, S. lineata, S. pinguis, 

 Producta aculeata, Strophomena pileopsis, Pccien piicatus, Terebratula as- 

 pera, T. IVilsoni, and T. lineata, 



Five — Spiri/era bisulcata, S. pinguis, Producta aculeata, Strophomena pileopsis, and Terebratula 



lineata, are also mountain-limestone species ; 

 One — Pecten piicatus, is believed to occur both in the mountain-limestone and Devonian strata ; 

 One — Spiri/era altenuata*, is peculiar to tlie Devonian series; 

 One — Terebratula aspera, is common to the Devonian and Silurian beds ; 

 Two — Spiri/era lineata and Terebratula Wilsoni, are true Silurian fossils, if the identification 



be right ; but the characters of the latter frequently lead to erroneous determinations. 



In the systeme calcareux inferieur five species of shells are specifically 

 mentioned with references, and ten of corals. 



The shells are, Spirifera atlenuata, Terebratula prisca, T. aspera, T. ex- 

 planata, and Spirifera lineata. The first is probably the shell peculiar to the 

 Devonian series, but if it be correctly identified it is a mountain limestone 

 species. Terebratula prisca and T. aspera are found, as already stated, both 

 in the Silurian and Devonian series ; Terebratula explanata is generally con- 

 sidered a variety of T. prisca, and Spirifera lineata is given with a doubt. 



The ten species of corals are, Fenestella (Retepora) antiqua, Anthoph/llum 

 bicostatum, Cj/athopht/llum dianthus, C. quadrigeminum, (including Manon 

 favosum, see Goldfuss, corrigenda, vol. i.,) C. ccsspitosum, Strombodes (C) 

 piicatus, Astrea (C.) ananas, A. (C.) pentagona, Favosites (Calamopora) spon- 

 gites, and F. {C.) polymorpha. 



* The shell called Spiri/era attenuata on the Continent is one of the most characteristic fossils 

 of the beds under consideration, being noticed in every published list ; but it differs essentially 

 from the mountain-limestone fossil called Spiri/era attenuata, in the ribs being simple and regular 

 in size, and in the greater projection of the raised central part of the upper valve. 



5 B 2 



