GEOLOGY OF PART OF SOUTH DURHAM. 181 



Quarter seams. It has been shown that if we take either seam 

 we find different groupings of genera and species as we vary the 

 district examined. In one part we have nothing but compressed 

 stems of large Sigillarice. In another large Catamites, and no- 

 thing more. Again, a few bords to the right or left and there 

 is a great abundance of ferns and few Calamites. While some 

 distance away we have a profusion of Lepidodendra, a few ferns, 

 and no Calamites. Then we come to acres and acres of roof 

 matter with scarcely a plant to be seen, but in which the shells 

 Anthracosia and Anthracoptera are not uncommon. Lastly, we 

 come to a region where the only fossils are the upright stumps 

 of large Sigillarice, scattered in (dangerous) profusion overhead. 



It would, in fact, be matter of no difficulty to take either the 

 Brockwell or the Five Quarter, as seen by us at the Newton Cap, 

 Old Etherley, Railey Fell, Lands, and Norwood collieries, and 

 term it a Sigillaria coal, a Calamite coal, a fern coal, or a coal 

 characterised by marine or esturine mollusca, just as we varied 

 the district examined. 



It is possible that some coal-fields may show a generic progres- 

 sion in their flora, such as that pointed out by Dr. Geinitz for 

 Saxony, though it seems to be expecting too much from palaeon- 

 tology to assume that any such progression should be found ge- 

 nerally characteristic of the Coal Measures. The flora of this 

 formation would appear to have been pretty nearly the same 

 throughout. Sigillaria, in some localities, may have preceded 

 Calamites, while ferns may have succeeded both, either in first 

 appearance or in period of maximum development ; but we 

 should rather ascribe such succession of Carboniferous vegeta- 

 tion to peculiarities due to local distribution than to any general 

 sequence of plant-life. 



"We have met with few animal remains in the Coal Measures. 

 The occurrence of Megalichthys Hibberti has been already men- 

 tioned. Its remains are rare. We have also alluded to the 

 presence of Anthracosia acuta, and Anthracoptera sp. in the roof 

 of the Brockwell coal. These, with the entomostracan Beyrichia 

 arcuata, found near Woodhouses, near Lands Pit, and in the 

 George Pit, Etherley, together with the common Coal Measure 



