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On some New Fossil Molluscs in the Carboniferous Slates of the Anthracite Seams of 
the Wilkesharre Coal Formation. 
By Isaac Lea. 
Mem. Am. Phil. Soc., The Acad, of Nat. Sci., &c. 
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 
“ Posodonomya 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 Griffith! states that he found many shells in 
the lower portion of the Carboniferous Limestone series of Ireland. He observed 
Cytherea , 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. Murchison^ 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 Palseontological Tables, assigns to it 
* Second Travels, p. 16. f Proceedings British Association, 1843, p. 42. 
% Geological Transactions, vol. 5, 2d series, p. 633. 
[From Journ. Acad. Nat. Sci., part 3, vol. ii., N. S —Read May 18th, 1852.] 
