1858.] DAWSON LOWEE COAL-MEASUEES. 67 



accTiniulatiiig, and discoloured and darkened by decaying organic 

 substances, partly of aquatic, and partly of terrestrial origin. 



Both the supply of sediment and tbe growth and preservation 

 of vegetable matter were on a smaller scale than in the true coal- 

 period, the only exception being the bituminous limestones and 

 associated dark shales of the latter, which in composition and aspect 

 often much resemble the beds now under consideration. 



These characters cause the Lower Carboniferous coal-measures to 

 present a very striking contrast with the coarse and often reddish 

 sediments which prevail in the marine parts of the Lower Carboni- 

 ferous series in the area in question. 



Before leaving this comparative view, it is necessary to remark 

 that it is precisely in those districts where the true coal-measures 

 are least developed that the lower series is most important. This is 

 not likely to be the result of accident. It shows that the physical 

 and vital conditions of the coal-measures originated as early as those 

 of the mountain-limestone, that locally these conditions may have 

 been contemporaneous throughout the whole period, but that in 

 some localities the estuary- and swamp -deposits first formed were 

 so completely submerged as to be covered by oceanic deposits, while 

 in others early marine beds were elevated and subjected to the 

 conditions of gradual subsidence and vegetable growth indicated in 

 the great coal-measures of South Joggins, Pictou, and Sidney. 



11. Flora of the Lower Coal-measures. — In IS'ova Scotia the lower 

 coal-measures are characterized by a great preponderance of Lepido- 

 dendra, and the leaves named Poacites, among their fossil plants. 

 The middle coal-measures are rich in Sigillarice and Ferns as well 

 as Lepidodendra ; and the upper coal-measures especially abound in 

 Coniferce, Calamites, and Ferns. These peculiarities may be local and 

 dependent on the facilities for the preservation of particular kinds of 

 plants; but they deserve more attention than they have hitherto 

 received, in connexion with the changes of physical condition which 

 have occurred during this long period, and with the accumulation of 

 the largest beds of coal in the middle coal-measures. It must be 

 confessed that the flora of the lower coal-measures is by no means 

 rich in species, though locally, as at Horton Blnff and Windsor, 

 there are great numbers of individual plants. 



1. Lepidodendrece. — In this group of plants Lepidodendron elegans 

 takes precedence as the most abundant species. At Horton and 

 "Windsor there are large numbers of prostrate trunks and branches, 

 sometimes with the leaves attached. In two distinct beds there are 

 erect stumps, apparently referable to this species. They are of 

 small size, but very numerous, and must have constituted dense 

 groves of these trees. Their roots appear to have been branching 

 and fibrous ; and no trace of Stigmaria was found in the underclays. 

 These trees must have grown in sandy clay ; and beds with fishes 

 and ripple-marks occur at no great distance both below and above 

 them. The quantity of prostrate trunks and branches overlying 

 one of these fossil forests would appear to indicate that the trees 



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