Reports and Proceedings — Geological Society of London. 575 



The radiolaria occur as casts in chalcedony in the jaspers and clay- 

 stones. The rocks dip at a high angle. No macroscopic fossils are 

 known with cei'tainty from these districts. 



In the Jenolan Cave district the radiolarian rocks consist of black 

 cherts and clay-shales overlying the Cave Coral Limestone, and of 

 greenish-grey shales underlying this rock. The series is traversed 

 by felsitic dykes, and the hardness of the cherts is attributed to 

 silica derived from the acidic dykes, I'ather than to that derived from 

 the tests of the siliceous organisms. 



It is at Tamworth that the radiolarian rocks are developed on 

 a gi'and scale ; their measured thickness amounts to 9,267 feet, after 

 allowing for an immense fault, and neither upward nor downward 

 limit is shown. The rocks consist of jointed claystones, black cherts, 

 lenticular siliceous radiolarian limestones, and coral - limestones. 

 Numerous beds of submarine tuff also occur. The claystones are 

 largely formed of radiolaria. In certain beds of the claystones, and 

 in some of the tuffs as well, impressions of Lepidodendron australe 

 are not uncommon; and beds of radiolarian limestone occur in close 

 proximity to the beds with these plant-remains, and radiolaria 

 moreover abound even in the same rock with the Lepidodendron 

 Impressions. 



At the eastern end of the Tamworth section, and also near the 

 westerly portion, there are limestones containing corals, which have 

 been determined by Mr. R. Etheridge, jun. They are similar to 

 those of the Burdekin Limestones of Queensland which belong 

 to the Middle Devonian, and the radiolarian rocks are thus shown 

 to belong to this period. 



Analyses of the radiolarian chert, cherty shale, shale, and siliceous 

 limestone prepared by Mr. J. C. H. Mingaye, F.C.S., are given ; and 

 from these it appears that, while the amount of silica in the chert 

 and shale ranges between 68 and 91 per cent., there is only 18 per 

 cent, in the siliceous limestone. 



Descriptions of numerous micro-sections, both of the sedimentary 

 and of the tufaceous rocks, are appended, and in their conclusions the 

 authors point to the remarkably fine-grained character of the materials 

 forming the base of the radiolarian cherts, jaspers, and shales, the 

 constituent particles not being more than 0-05-0'02o mm. (^^o^ to 

 xoVo inch) in diameter. They are of opinion that the radiolaria were 

 deposited in clear sea-water, which, though sufficiently far from land 

 to be beyond the reach of any but the finest sediment, was nevertheless 

 probably not of very considerable depth. 



2. " On the Eadiolaria in the Devonian Eocks of New South 

 Wales." By G. J. Hinde, Ph.D., F.R.S., F.G.S. 



Hand-specimens of the various radiolarian rocks discovered by 

 Messrs. David and Pittman in New South Wales were forwarded to 

 the author, and from them numerous microscopic sections were 

 prepared. In the chert and jasper rocks of the Jenolan, Bingara, 

 and Tamworth districts, the radiolaria were for the most part in the 

 condition of casts filled with chalcedonic silica and without structure, 



