VOL. xvii. (3) FOSSIL PLANTS— FOREST OF DEAN 323 



face of a bedding-plane showing portions of fronds or stems. 

 The slab should then be split up, layer by layer, with a chisel. 

 Repeated visits to the same waste-heap form the secret of 

 success in fossil plant-collecting. 



I do not propose to discuss the geology of the Forest of 

 Dean here. The subject has been dealt with repeatedly by 

 others in the Proceedings of the Club. We are concerned 

 here solely with the Productive Coal Measures, that is to say, 

 the measures in which the coal-seams occur. It will suffice 

 to point out that these seams fall naturally into three divi- 

 sions, an Upper, Middle and Lower, according to their out- 

 crops, as is shown on any large scale geological map of the 

 Forest. In the centre of the field, we find two closely asso- 

 ciated seams, the Woorgreens Coals, which together form the 

 First Division of the Productive Measures. These are separa- 

 ted from the next seams below by a considerable thickness of 

 barren rocks, about 116 yards in all, consisting chiefly of 

 shales with some beds of sandstone. We next find eight 

 seams of coal, closely associated and with parallel outcrops. 

 These form the Second Division. The Crowdelph Coal is the 

 highest of these, and the Churchway High Delph the lowest. 

 The beds between the seams are chiefly shales. The lowest 

 or third Division consists of a group of six coals, of which 

 the No Coal is the highest and the Trenchard Coals the lowest. 

 This division is very different to those above. The coals are 

 more wide'y separated, and their outcrops are very irregular, 

 and much less nearly parallel. Further, while shales and 

 sandstones prevail in the higher portion, the lower consists of 

 a very massive series of sandstones without shales, which 

 form the well-known Forest of Dean Stone. 



With this short summary of the Productive Measures, 

 I propose to enumerate briefly the plants found at the prin- 

 cipal collieries working the coals of one or other of the three 

 divisions. 



