FORMATION OF COAL. 195 



over every seam that I have yet examined in the Bristol coallield. 

 Next follows a bed of harder duns e : in this are other fossils 

 besides the one just described (there are a few others in the beds 

 below), they are chietly of the genus 6igillaria, SpJieno])teriSj and 

 Calamites approximatus. 



If we pass to another seam we find the flora over the coal 

 slightly different. Thus if we take the Great Toad Vein which is 

 above the last seam, we still find Cordaites ; Sigillaria is much 

 more abundant ; Asteropkijllites is common ; Lepidostrohus , 

 Lepidophloios and others also occur. 



The Bristol coalfield is not so rich in plants as some others, — 

 no trace of a fauna has yet b^en discovered. If we take the South 

 Staffordshire coalfield we meet with an abundance of both, as 

 proved by Mr. J. Ward, F.G.S., and others. In the black shale of 

 the " deep mine ironstone,'' worked chiefly at Longton, good 

 specimens of fish have been found, of which the genus Paloeoniscus 

 is characteristic. 



The '' Rag " mine at Fenton also contains fish remains, as do 

 other shales and ironstones in the district. Of the Mollusca — 

 Brachiopoda, Lamellibranchiata, Gasteropoda, Cephalopoda, and 

 Annelida, are all well represented. The flora is abundant, but has 

 not been so fully described as the fish. No matter into what part 

 of the world we go, wherever coal occurs of carboniferous date, the 

 similarity of the flora is most striking. While in the Black 

 Warrior Coalfield of Alabama I collected specimens so familiar 

 to me, that it was like meeting old friends. 



The trees most numerous during the carboniferous period were 

 the €alamites, Sigillaria, and Lepidodendrons, Calamites have 

 long been considered to be allied closely to the modern Equisetaceae 

 or *" Horse Tails," which view is supported by Mr, Carruthers j 

 but Professor Williamson points out that they have no sheath to each 

 joint of the stem, nor, probably, hygrometric (absorbing water) 

 elaters to each spore which is the case with the Equisetaceae. 

 Calamites are always found hollow, except at the nodes : it has 



