188 



THE CARBONIFEROUS SYSTEM. 



quiet waters were then filled up with clay and sand, the latter 

 ripple-marked, and with drifted vegetable fragments. Another soil 

 was formed above these beds, and on it we find an inch of coal, with 

 flattened SigillaricB^ which probably once grew on the underclay. 

 This terrestrial surface was succeeded, as usual, by waters swarming 

 with Naiadites and fish, and on these were spread out beds of sand 

 and mud, with ripple-marks, drift trees, and evidences of partial 

 denudation by currents. A terrestrial surface was again restored, and 

 four inches of coal were accumulated ; but the waters again prevailed, 

 and in the coal itself we find Naiadites^ Cythere, and plants covered 

 with Spirorbis, indicating that these creatures took possession while 

 the vegetable matter was still recent, and probably much of it in an 

 erect position. A terrestrial surface was, however, soon restored ; for 

 in the shale which covers the coal there is a fine ribbed stump, two 

 feet in diameter, and displaying on its roots the markings of the true 

 Stigmaria ficoides, as well as the rootlets in situ in the shale. This is 

 the first instance we have here yet met with of the distinct connexion 

 of an erect ribbed stem with its Stigmaria roots. The causes of the 

 difficulty of observing the roots and stem in connexion will be stated 

 in the sequel. 



The next Subdivision is in great part the result of somewhat rapid 

 mechanical deposition. It contains thick beds of sandstone, deposited 

 by currents which have undermined wooded banks, or passed through 

 recently submerged forests, for they contain numbers of trunks of 

 different trees, retaining their bark and surface markings. Its coals 

 are few and insignificant. There are, however, erect trees and Cala- 

 mites at three levels ; and one of the trees springs from a shade loaded 

 with Cordaites which may have grown around its base. 



Here we may pause for a little, to note the appearance of some of 

 the new vegetable remains to which we have been introduced. We 

 have found a Sigillaria with distinct markings, namely, its sides marked 

 with bold ribs, having the effect of the flutings of a Grecian column, 

 and these ribs dotted with vertical rows of leaf-scars. We have also 

 seen a distinct instance of a Sigillaria attached to its Stigmaria roots 

 still spreading through the soil. (See Fig. 30, page 180.) Let us 

 now endeavour to form an idea of the trees of this singular genus. 

 Imagine a tall branchless or sparsely branching trank, perhaps two 

 feet in diameter, and thirty feet in height. (One has been traced to 

 the length of forty feet in the roof of the Joggins main coal-seam.) 

 The trunk is covered with a thick bark, very smooth, and ribbed 

 regidarly, and is clothed to the summit with a dense mass of leaves, 

 probably of lengthened and grass-like forms. Such trees must have 



