200 



THE CARBONIFEROUS SYSTEM. 



usual fossils and resting on coal. This is a case precisely similar to" 

 that which terminates our 23d group, except that in this last case the 

 conditions favourable to the formation of bituminous limestone probably 

 continued longer. 



The next is another barren group of chocolate and gray shales, with, 

 gray sandstone occasionally rippled, and with fragments of drift-wood. 

 This is the filling up of the shell-fish-inhabited waters, in the manner 

 already so frequently noticed. In one of its beds I observed rain- 

 marks, and a series of footprints, probably of a small reptile ; and it was 

 here that Mr Marsh found the vertebrae of the largest reptile yet 

 discovered at the Joggins, Eosaurus Aeadianus. 



Subdivision XXVII. is another succession of underclays and smalt 

 coaly layers. It is remarkable for the very pyritous character of many 

 of its beds, an indication of the action of sea-water. The most 

 remarkable part of this group is that represented in Fig. 41. It 



Fig. 41. — Section from the lower part of Subdivision 



XXVII. 



7 6 5 



1. Shale. 2. Shaly coal, 1 foot. 3. Underclay with rootlets, 1 foot 2 inches. 



4. Gray sandstone passing downwards into shale, 3 feet. Erect tree with Stigmaria roots (e) 



on the coal. 



5. Coal, 1 inch. 6. Underclay with roots. 10 inches. 



7. Gray sandstone, 1 foot 5 inches. Stigmaria rootlets continued from the hed ahove; erect 

 Catamites. 8. Gray shale, with pyrites. Flattened plants. 



includes a bed of erect Calamitcs and an erect tree with distinct Stig- 

 maria roots. The underclays are here so crowded on the erect plants, 

 that the rootlets of one underclay pass downward among the erect 

 Calamites, and the rootlets of another pass beside and within the cast 

 of the erect tree, the surface markings of which they have helped to 



