1853.] 



DAWSON — COAL-MEASURES, NOVA SCOTIA. 



21 



The wood of this tree shows, in the longitudinal section, a cellular 

 tissue, precisely similar to that of the Coniferse ; the cross section 

 shows only elongated cells, but is very badly preserved. A tree of 

 this description is not likely to liave been more perishable than the 

 SigillaricB, which, in the same situation, remained until 9 feet of sandy 

 mud had accumulated. I suspect, therefore, that this stump may be 

 the remains of a coniferous forest, which preceded the SigillaricB in 

 this locality, and of which only decaying stumps remained at the time 

 when the latter were buried by sediment. This is the more likely, as 

 the appearances indicate that this tree was in a complete state of 

 decay at the very commencement of the sandy deposit. The rep- 

 tilian remains found in these beds give them more than ordinary 

 interest, and may excuse a reference to the probable history of their 

 formation more detailed than in the case of other parts of the section. 



Fig. 2. — Section of middle part of Group XV. (p. 6), in which the 

 Dendrerpeton and Land-shells have been found. See 

 Quart. Journ. Geol. Soc. vol. ix. p. 61. 



1. Uriderclay, with rootlets of Sligmaria, resting on grey shale, with two thin coaly seams. 



2. Grey sandstone, with erect trees, Calaniites, and other stems : 9 feet. 



3. Coal, with erect tree on its surface : 6 inches. 



4. Underclay, with Sligmaria rootlets. 



a. Calamites. c. Stigmaria roots. 



b. stem of plant, undetermined. f/. Erect trunk, 9 ieet high. 



(1.) The Stigmaria-underclay, 4, shows the existence of a Sigillaria 

 forest, on the soil of which was collected sufficient vegetable matter 

 to form 6 inches of coal, which probably represents a peaty bog 

 several feet in thickness. (2.) On this peaty soil grew the trees 

 represented by the stump of mineral charcoal mentioned above, and 

 which were probably coniferous. This tree, being about 1 foot in 

 diameter, must have required about fifty ye.ars for its growth to that 

 size. It was then killed, perhaps by the inundation of the bog. 

 (3.) During the decay of the tree last mentioned, Siyillarice, d, grew 

 around it to the diameter of 2 feet, when they were overwhelmed by 

 sediment, which buried their roots to the depth of about 18 inches. 

 At this level Calamites, a, and another Sigillaria began to grow, the 

 former attaining a diameter of 4 inches, the latter a diameter of about 

 1 foot. (4.) These plants were in their turn imbedded in somewhat 

 coarser sediment, but so gradually that trees with Stigmarian roots, c, 

 grew at two higher levels before the accumulation of mud and sand 



