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ART. XXI. — On some New Fossil Molluscs in the Carboniferous Slates of the An- 

 thracite Seams of the Wilkesbarre Coal Formation. 



By Isaac Lea. 



It is rare to find any of the Molluscs in the slates of the coal bearing deposits, either 

 in this country or in the foreign Carboniferous coal strata. Mr. Lyell observes the 

 fact, but mentions an exception, in the Richmond strata, where a species of 

 " Fosodonomija is in such profusion as to divide the shaly beds, like the plates of 

 Mica in Micaceous shales." At Frostburg, in Maryland, in the black shale, resting 

 on a seam of coal three feet thick, he found seventeen species.* 



It is so rare, in Pennsylvania, to find impressions of Molluscs in the shales 

 immediately connected with the seams of coal, that I have not, in more than thirty 

 years observation, met with more than one instance of the kind. This specimen 

 taken, by myself, from a mass which had been brought out of a working coal mine, 

 above Wilkesbarre, Luzerne county, on the Susquehanna, has several different 

 species, belonging to at least two genera, which are accompanied with several scales 

 of fishes, evidently belonging to the Ctenoidians. 



In the calcareous strata and sandstones of the Carboniferous System, fossils of the 

 Molluscs are very abundant ; but in the red and grey sandstones of the inferior strata, 

 Devonian, they are rare. Mr. Richard Grifl&thf states that he found many shells in 

 the lower portion of the Carboniferous Limestone series of Ireland. He observed 

 Cijtherea, Modiola, Nucula, &c., and mentions that fossils of the genus Modiola have 

 been considered to belong to the Old Red Sandstone or Devonian System, but as he 

 had discovered these fossils in great abundance, as high up as the carboniferous 

 slates, and far above the arenaceous limestones, he should include them among^ the 

 fossils belonging to the Carboniferous System ; and hence, as these fossils have been 

 met with in the red shales, which alternate with red and grey sandstones and lime- 

 stones, near the bottom of the series, and among those strata which he had hitherto 

 considered to belong to the upper portion of the Old Red Sandstone, he thought he 

 was warranted in including it in the Carboniferous Series, (p. 46.) 



Professor Sedgwick and Mr. MurchisonJ found the genus Posidonia abundant, 

 both in the upper and lower limestone shales of the true Carboniferous series of 

 England and Ireland; and D'Orbigny, in his Palaeontological Tables, assigns to it 



* Seconil Trarels, p. 16. f ProceediDgs British Association, 1843, p. 42. 



J Geological Transactions, vol. 5, 2d series, p. 633. 



