406 



THE CARBONIFEROUS SYSTEM. 



tus cora, Terebratula sacculus, Spirifer glaber, and a species of Euom- 

 phahis. The limestone is sufficiently soft to allow fine specimens of 

 these shells to be detached by weathering. 



The Coal measures are by far the most interesting part of this area, 

 and are well exposed on the north side of Sydney Harbour, and on the 

 south end of Boulardarie. Mr Brown has published an elaborate, 

 section and description of them as they occur at the former place, 

 from which the following facts are gleaned : — 



u The productive Coal measures cover an area of 250 square miles ; 

 but, owing to several extensive dislocations, it is impossible to 

 ascertain their total thickness with any degree of accuracy ; from the 

 best information in my possession, I conclude that it exceeds 10,000 

 feet. We have one continuous section on the north shore of Boulardarie 

 Island, 5400 feet in thickness, and in the middle portion of the field 

 several detached sections, varying from 1000 to 2000 feet in thickness, 

 whose exact relative positions have not yet been determined ; although 

 it is quite clear that they are higher up in the formation than the 

 highest beds of the Boulardarie section." 



Mr Brown then proceeds to describe the section on the north-west 

 side of Sydney Harbour, from Stubbard's Point to Cranberry Head, a 

 distance of 5000 yards, and exhibiting a vertical thickness of 1860 

 feet of beds. The dip is N. 60° E. 7°. Of these beds he gives a de- 

 tailed section, including 34 seams of coal, and 41 underclays with 

 Stigmaria or fossil soils. The whole of the beds composing the section 

 are summed up as follows : — 



Erect trees and calamites occur at eighteen distinct levels. The 

 greater number are Sigillariae, many of them with distinct Stigmaria 

 roots, and a few are Lepidodendra. They occur in circumstances very 

 similar to those of the erect trees at the Joggins already described. 

 Mr Brown's various papers on these fossils gave to the geological 



