548 GREAT .SP::RPENTINE-B{5r/1' OF N'EW SOUTH WALES, V., 



fine grey rocks of quartzitic appearance, and greener masses, like 

 altered tuffs and greywackes. Higher up, the quartzitic rock 

 becomes more coarsely granular, and contains scattered crystals 

 of felspar, and it is intersected by an occasional vein of jasper. 

 The microscope reveals that the greenish rocks are highly altered 

 silicified and strained tuffs, while the rocks of a quartzitic ap- 

 pearance are chiefly much crushed and metamorphosed kerato- 

 phyres of a type that finds no analogy among the rocks of the 

 Middle Devonian Series. All the rocks of this hill seemed to 

 have been recrystallised under the metamorphosing influence of 

 the adjacent granite. The details of the petrography are given 

 below. 



About a quarter of a mile south of this, is a large mass of 

 tuff-breccia, lying east of the serpentine, but ver}^ closely re- 

 sembling some of that to the west in the Middle Devonian 

 Series. 



The purely sedimentary rocks, in addition to the banded 

 cherts, are jaspers, phyllites, rarely so fissile as slates, and gener- 

 ally pale brown or green in colour. These pass into jaspers, or 

 are veined or interstratified with jasper. There is no exact 

 analogy for these rocks among those of the higher series, unless 

 they are derived from the Upper Devonian mudstones, which 

 seems unlikely. It is these rocks, if any, that are to be con- 

 sidered of Lower Devonian age. It is quite impossible to esti- 

 mate their thickness. 



2. The Tamworth Series of Middle Devonian age. 

 The main interest in the stratigraphical portion of this paper, 

 lies in this division of the geological record. We cannot yet, 

 however, be certain as to the relative thicknesses of the subdivi- 

 sions that have been adopted. The zones proposed depend partly 

 on their lithological character, partly on the fauna of their 

 associated limestones. In place of the single horizon of limestone 

 formerly recognised, three are now believed to be developed, 

 though the position of one of them is scarcely known at present. 

 The three, in probable chronological order, are as follows : the 

 Nemingha Limestone, the Loomberah Limestone, and the Moore 

 Creek Limestone. 



