36 PEOF. T. W. E. DAYID & ME. E. F. PITTMAN [Feb. 1 899, 



magnetite) are present. The felspars are chiefly plagioclase. A 

 devitrified, spherical, yellowish glassy enclosure is present in the one 

 quartz-grain visible in this slide. The augite is mostly granular or 

 in angular fragments, and is pale greenish-grey to almost colourless. 

 A yellowish-green decomposition-product, probably epidote, occurs 

 interstitially and in minute veins. 



Slide No. 621. — Cut from an included rounded block or pebble 

 of the Cleary's Hill volcanic agglomerate. The rock is porphy- 

 ritic, composed of phenocrysts of plagioclase, some orthoclase, 

 augite, and a few crystals of sphene : these are distributed through 

 a rather opaque, whitish-grey, felsitic base. The phenocrysts are 

 mostly idiomorphic, but a few have suffered somewhat from fracture 

 and corrosion, though not nearly to the same extent as the pheno- 

 crysts in the tuff proper surrounding the fragment. The phenocrysts 

 are also fairly free from decomposition. The sphene, which is 

 idiomorphic, seems more pronounced in this section than in the 

 22-yards tuff from Tamworth Common. One crystal of rather 

 opaque calcite is visible. The rock may be described as an augite- 

 diorite porphyry or porphyritic andesite. It appears to be closely 

 allied to the tutfs, but to be slightly more basic. 



VI. CONCLTTSIONS. 



The following conclusions may be provisionally drawn from the 

 observations recorded in this paper : — 



(1) That radiolaria were very important rock-forming organisms 



in the Palaeozoic rocks of New South Wales, as {a) near 

 Tamworth a thickness of strata exceeding 9000 feet, inclusive 

 of submarine tuffs, is formed chiefly of tests of radiolaria; 

 *■ (h) these rocks extend for at least 85 miles northward 

 to Bingara, and if the Jenolan Cave radiolarian rocks be 

 on the same horizon, 200 miles southward, a total distance 

 of at least 285 miles ; (c) radiolaria are present in the bulk of 

 these rocks at the rate of about one million to the cubic inch. 



(2) That if the one bed of conglomerate observed near Tam- 



worth be not referable to the Radiolarian Series, as appears 

 probable, the whole of the strata exposed are remarkably 

 fine-grained, the fragments forming the base of the shales and 

 cherts and red jaspers being not more than from 0*05 to 

 0*025 mm. in diameter. 



(3) That the fact that a thick bed of coral-limestone and 



plant-beds, on three horizons, are interstratified with the 

 Eadiolarian Series, taken in conjunction with the previous 

 conclusion, shows 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. 



(4) That the supposed absence of fossils from the Palaeozoic 



sedimentary rocks over wide areas in the New England 



