258 T. W. EDGEWORTH DAVID. 



locality, partly of freshwater and partly of volcanic origin, and is 

 characterised by an extraordinary predominance of Rliacopteris, 

 to the entire exclusion, as far as my observations extend, of 

 Lepidodrendon. The lower half contains Lepidodrendon associated 

 with Rhacopteris, and interstratified with them, there is at least 

 one bed containing marine Carboniferous fossils. 



Mr. Mackenzie in his sections published in "Mines and Mineral 

 Statistics of New South Wales," and in " Mineral Products etc. 

 of New South Wales," shows that on a horizon about 2,000 feet 

 below the topmost of these Rhacopteris beds there are the following 

 coal seams and strata, the upper being placed first : — 



Ft. In. 



2 3 Inferior coal and indurated clay. 



2 Chert shale and conglomerate. 



5 Coal, inferior. 

 Beds of limestone from a few feet up to eight feet thick are 

 associated with the Lepidodrendron beds, and just above the lime- 

 stone is a remarkably persistent bed of magnetic ironstone from 

 one foot up to eight feet thick, which is interbedded with these 

 Carboniferous strata. The bed of magnetic ironstone has evidently 

 been formed by the mechanical concentration, through the action 

 of the waves on a sea beach, of crystals and grains of magnetic and 

 titaniferous iron out of the volcanic tuffs and massive eruptive 

 rocks, which are so plentifully interspersed through this group. 

 The bed was therefore formed in Carboniferous times in a manner 

 analogous to that in which the iron-sands of Taranaki, New Zea- 

 land are now accumulating. 



No exact upward limit can at present be assigned to this group 

 but it is probable that there is somewhat of an unconformity 

 between it and the rocks of the succeeding group. The junction 

 line however is rendered somewhat complex and obscure by the 

 great development of volcanic rocks, which are observable almost 

 everywhere in the type district of Maitland along the line of junc- 

 tion, and which were contemporaneous either with the uppermost 

 strata of the Rhacopteris group, or with the lowest strata of the 

 succeeding Glossopteris group. 



(B.) Associated Eruptive Rocks. 



These are partly contemporaneous and partly subsequent. 



(i.) Contemporaneous. The contemporaneous eruptives are 

 chiefly diabasic basalt lavas and tuffs, and felsite lavas and felsite 

 tuffs. Some of the tuffs are very coarse containing blocks up to 

 three feet in diameter. They are nearly all partly of sedimentary 

 origin, as the component particles are mostly rounded, and graduate 

 into arkose sandstones. But for the occasional presence of pebbles 

 and the intercalated beds of carbonaceous clay shale, these arkose 

 rocks might easily be mistaken for granites. It is, as yet, a little 



