16 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 2, 



shells of Cypris and fragments of Modiolce. This last bed accumu- 

 lated, no doubt, very slowly, in quiet waters which must have inun- 

 dated, for a long period, the tract formerly occupied by a forest. 

 This inundation was not accompanied by the deposition of mechanical 

 debris, — an evidence either that it was very gradual, or that the spot 

 was in the interior of a thick and wide swampy jungle, into which no 

 currents sufficiently powerful to carry sediment could find their way. 

 After a time the locality again became a soil, on which Sigillarice 

 again flovirished, and accumulated the material of 6 inches of coaly 

 matter before, by a farther subsidence, the water and its tenants were 

 restored, and continued, with various interruptions occasioned by the 

 influx of muddy sediment, to occupy the ground until 24 feet of 

 thickness were accumulated, showing either that the original subsi- 

 dence was of more than that extent, or that the surface was continu- 

 ally going down as rapidly as it was elevated by deposition. At 

 length, however, the accumulation of 1 6 feet of mud, perhaps accom- 

 panied by elevatory movement, restored a terrestrial surface, which 

 became clothed with trees and Catamites. A cast in sandstone of 

 one of these trees, 8 inches in diameter, showed large rhomboidal 

 markings, like the leaf-scars of Lepiclodendron. A number of erect 

 Calamites in this deposit were also seen standing in the cliff. 



The next group shows the submergence, and burial under mud and 

 sand, of this soil, with its forest and calamite brake. I observed no 

 fossils in this group, but Mr. Logan has noted Stigmaria in its upper 

 part in situ. 



In Group III. we have a recurrence of the same circumstances 

 observed in Group I. A soil supporting Sigillaria, and covered with 

 vegetable mould, was submerged in waters inhabited by Modiola, 

 Cypris, and fish ; and then, for a long time, the locality was alter- 

 nately a swamp and an estuary or lagoon. Only one underclay 

 remains in these beds ; and there are no erect trees, nor can these be 

 expected. Coal and bituminous limestone are of too slow growth to 

 admit of the preservation of trees in situ ; and no instance occurs in 

 the Section of erect plants passing through beds of these kinds. 



Group IV. is a thick accumulation of sand and clay, which at one 

 level has entombed an erect ribbed tree, and at another a thicket of 

 Calamites. There were two terrestrial surfaces, sufficiently permanent 

 for the growth of these plants, but probably not for that of coal. 

 This period, as contrasted with the last, well shows the different 

 results of rapid and slow accumulation of detritus. In the one we see 

 little organic matter, but the rapid burial of growing plants has pre- 

 served their forms in the natural position. In the other we have 

 considerable animal and vegetable accumulations ; but decay has had 

 time almost entirely to destroy the external forms. These differences 

 are characteristic of many other parts of the Section. 



Group V. is a return, but on a smaller scale, to the circumstances 

 of Group III. It is chiefly remarkable for a bituminous limestone 

 immediately overlying an underclay, without any coal between. 

 Either no peaty matter grew on this soil, or it had time to decay be- 

 fore the accumulation of the calcareous deposit. The limestone itself. 



