220 



PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



occur in the Calciferous Sandstone — Euomphalus 4 species, Lacuna 

 I, Littorina 2, Loxonema 2, Macrocheilus 4, Murchisonia 3, Natica 1, 

 Naticopsis 1, Pleurotomaria 3. 



The Lower Limestone Shales contain 50 species, which, with one 

 exception (Turbo appropinquans), are also those of the Carboniferous 

 Limestone above ; or 49 of the 50 occur also in the massive lime- 

 stones. 



The Yoredale beds (the Upper Limestone Shales of some authors) are 

 poor in Gasteropoda; only 7 genera and 10 species appear to be known. 

 Clearly this must be the result of imperfect collecting rather than 

 of almost total absence of species. "We know that both the Lower and 

 Upper Limestone Shales are impure argillaceous limestones, and not 

 favourable to the presence of the Mollusca at the time of deposition 

 or to the preservation of organic structure afterwards : but we see here 

 the 7 genera only represented by 10 species ; they are : — Euomphalus 

 catillus, Sow. ; Loxonema constricted Sow. ; Macrocheilus curvilinea, 

 Phill. ; M. imbricatus, Sow. ; M. rectilinea, Phill. ; Murchisonia 

 fusiformis, Phill. ; Naticopsis plicistria, Phill. ; Pleurotomaria lim- 

 bata, Phill. ; P. tumida, Phill. ; and Turritella tenuistria, Phill. 

 The Millstone Grit, as we should expect, contains but a small 

 Gasteropod fauna ; such arenaceous deposits suit not the habits of 

 this group of Mollusca ; only 3 genera and 3 species are known — 

 Natica variata, Phill. ; Pleurotomaria limbata, Phill. ; and Murchisonia 

 fusiformis, Phill. The Pelagic Cephalopoda in the same beds, as we 

 shall see, number no less than 33 species ; but the sandy and muddy 

 beds of the shore was not their habitat ; they are not such good wit- 

 nesses in the beds in which they are found as the ordinary Lamelli- 

 branchiata and Gasteropoda. The Lower Coal-measures alone yield 

 Gasteropoda ; none are known either in the Middle or Upper. 7 genera 

 and 19 species are recorded from this division : — Euomphalus Gloveri, 

 Brown ; Littorina obscura, Sow. ; L. solicla, De Kon. ; Loxonema 

 galvani, Baily ; L. minutissima^ Baily ; L. Oweni, Brown ; L. reticu- 

 lata, Brown ; Macrocheilus, 4 species ; Natica veiusta, Sow. ; Nati- 

 copsis plicistria, Phill. ; Pleurotomaria limbata, Phill. ; P. usocona, 

 Sow. ; Turritella, 4 species. 



Middle Coal-measures none. 



Upper Coal-measures none. 



