part 1] THE WESTPHALIAN, ETC. OF EAST GLAMORGAN. 71 



land producing extensive open marshes. This prolonged period 

 ranged from Two-Foot Nine Seam to Pentre Seam times; then 

 a c3'-cle occm-red with an emerging land-surface culminating 

 in upland conditions. This happened during Ahergorky Seam, 

 No. 3 Rhondda Seam, and No. 2 Rhondda Seam times. 



The variation in the different classes of plants as to distribu- 

 tion would alter in the sediments forming the shales of the ten 

 horizons, and conform in a greater or less degree Avith the gradual 

 changes which took place in the land-surface. The sea-bottoms, 

 with their sediments and plant-remains, are always a faint reflex of 

 the distribution of these plants on the surface of the land. 



There is no doubt that too much stress has been laid on the 

 swampy conditions prevalent during Coal-Measure times, for there 

 is good reason to believe that elevated land-surfaces were to be 

 found then as now, and that the upland portions were clothed 

 with Cordaitales and ferns and fernlike plants. It is difficult to 

 conceive that the higher portions of the upland surface in Coal- 

 Measure times were entirely devoid of vegetation. 



The results of this investigation may be summarized as follows: — 



(1) Although plants show great similarity over a considerable area at the 



same horizon, they show great dissimilarity over small vertical dis- 

 tances, that is, from shales overlying one seam to another. 



(2) A period of Lycopods, especially conspicuous during Two-Foot Nine and 



Pentre Seam times, with a paucity of ferns and fernlike plants. 



(3) A period before and after, when ferns and fernlike plants occurred in 



abundance, with Lycopods rare. 



(4) The comparative persistence of Cordaitales and Equisetales throughout 



all the horizons. 



(5) A lack of persistency of the Filicales and Pteridosperms and of the 



Lycopods. One class was found to react upon the other, thus causing 

 one to be predominant, whereas the other class was very scanty and 

 vice versa. 



(6) The common association of Calamites and Cordaites leaves in the same 



slabs of shale, and also the common association of Lepidodendron 

 and Lepidostrohus on the same blocks of shale. 



(7) A cycle of depressed land- surface seemingly prevailed during Two- 



Foot Nine and Pentre Seam times, possibly forming extensive open 

 marshes which would favour the Lycopods ; whereas, before and after 

 this cycle of depression, more elevated land- surfaces prevailed, 

 favouring the ferns and fernlike plants. 



(8) When a genus proved common in the field, the number of species 



contained within that genus was found to be decreasing in the ratio 

 of 5 to 3. 



(9) There was probably a geological break at the time of formation of the 



coal-pebbles, and also a palaeontological break at the base of the 

 Staffordian Series. Coal-pebbles suggest the former break, and the 

 43 new species of plants suggest the latter. 



(10) Forty-five new species of plants have been added to the records of 



the South Wales Coalfield, and seven new species not previously 

 recorded in Britain have been found. One new type of insect was 

 discovered. 



