170 Notices of Memoirs — Dr. Arber — Flora of Forest of Dean, etc. 



Measure floras of other British coalfields, though the following species 

 which occur in the Forest have not previously been recorded from this 

 horizon elsewhere : — 



Annularia galioides (L. & H.). 

 Sphenophylltmn majiis (Bronn). 

 Mariopteris latifolia (?) (Brongn.). 

 Lepidodendron dichotomum, Sternb. 



Sigillaria rugosa, Brongn. ; S. trigona, Sternb. ; 8. brardi, Brongn., 

 var. denudata (Goepp.). 



The flora of the Forest of Dean is contrasted with those of the 

 neighbouring coalfields. As compared with the Radstock flora, there is 

 found to be a general agreement, though there are important differences 

 in detail, which are more marked than those which exist between 

 the known floras of Radstock and Bristol. These differences, liowever, 

 do not appear to indicate any considerable disagreement as regards 

 the horizon, for the percentage of Stephanian plants present is 

 approximately the same in each case. They are best explained as 

 local variations in the distribution of the flora of the period. 



The horizon of the so-called Millstone Grits, below the Tipper Coal 

 Measures and above the Carboniferous Limestone, is discussed. 

 Reasons are advanced in support of the view that the Upper Coal 

 Measures of tlie Forest overlie unconformably the so-called Millstone 

 Grits, which in reality are the higher beds of the Carboniferous 

 Limestone Series, which here have an arenaceous facies. True Mill- 

 stone Grits, as well as Lower, Middle, and Transition Coal Measures, 

 are absent in the Forest of Dean. 



The relationships of this coalfield to the neighbouring coalfields 

 of the West of England and South Wales are discussed from the 

 palaeobotanical standpoint. It is found that the Forest of Dean basin 

 exhibits no obvious relationship, either to the South Wales or to the 

 Radstock-Bristol coalfields. 



The Pennant Grits of South Wales belong to a lower horizon than 

 the markedly arenaceous series (the 'Forest of Dean Stone') of the 

 third division of the Forest. The Radstock-Bristol and Forest of 

 Dean basins are believed to be related tectonically, though not to the 

 main axes of South Wales and the Mendips, but to a secondary 

 cognate uplift, stretching north and south, and approximating to the 

 valley of the Severn. On the other hand, the Forest of Dean does not 

 appear to be related to the Welsh borderland series of coalfields, 

 stretching from Newent to Shrewsbury. 



In the case of the Forest of Dean it seems evident that the Lower 

 Carboniferous rocks and the Old Red Sandstones of the area remained 

 elevated above sea-level, and were denuded until the beginning of 

 Upper Coal Measure times, whereas in South AVales depression and 

 deposition set in in Middle Coal Measure times, and in the Radstock- 

 Bristol area during the Transition Coal ^Measure period. Thus, on 

 the palaeobotanical evidence, the relationships of the coalfields of the 

 West of England and South Wales have proved to be more complex 

 than has hitlierto been supposed, and this appears to be due, in part 

 at least, to the coincidence of three distinct axes of elevation in the 

 neighbourhood of the Forest of Dean. 



