Yol. 55.] ON PALEOZOIC KADIOLARIAN K0CK8 IN N. S. WALES. 35 



of felsitic rock and a few large angular fragments. The last- 

 mentioned are from 1 9 to 25 mm. long, by about 1*5 mm. thick. 

 They are respectively green and black radiolarian cherts. 



The matrix in which the fragments are embedded has the appear- 

 ance of a dark bluish-grey to greenish-grey limestone, weathering 

 superficially into a brown friable rock resembling £ath brick. It 

 is chiefly formed of sub-translucent to opaque calcite, with small 

 fragments of cryptocrystalline felsitic material containing small 

 felspar-crystals about 0'36 mm. long by 0'125 mm. thick. (It 

 is improbable that the small crystals are chiastolite, as they show 

 straight extinction.) The margins of these fragments are slightly 

 more opaque than their inner portions. Pyrites is present in 

 small crystals and crystalline aggregates, and so also are some 

 dark streaks, apparently carbonaceous. In places there are patches 

 of clear calcite, about 25 mm. in diameter, very much corroded 

 at the edges, and shading off into the surrounding groundmass. 

 A green mineral, feebly pleochroic, which seems of secondary 

 origin, is associated with these patches of calcite, and also occurs 

 interstitially in patches and streaks throughout the slide. It is of 

 about the sSne hardness as serpentine. Small felspar-crystals 

 measuring 0*5 mm. by 0*125 mm. are enclosed in some of these 

 green patches. There are a few remains of indeterminable calcareous 

 organisms present in the calcareous base. 



Slide No. 562, Eth. (4794).— The rock of this slide consists of 

 alternating laminse of dark cherty clay stone and tuff. The laminae 

 are from 3-12 to 6*25 mm. thick. The tuff-rock is composed of 

 angular corroded fragments of plagioclase and orthoclase, from 0'05 

 to 0*36 mm. in diameter. Cryptocrystalline felsitic fragments are 

 present, similar to those in slide No. 249 (p. 34), but not so con- 

 spicuously developed. Quartz-grains with corroded edges are 

 interspersed with the felspars, and measure from 0'25 to 0*36 mm. 

 in diameter. The junction- line between the tuff and the radiolarian 

 chert, in the case of the coarse-grained bands of tuff, is very sharp. 

 In the case of the fine-grained tuff, the junction-line is less defined, 

 and there are traces of a few felspar-crystals in the substance of 

 the chert, but in close contiguity to the tuff. A little pyrites and 

 a little magnetite are present in the tuff. The dark streaks in the 

 chert are apparently carbonaceous. Several radiolaria may be 

 recognized in the cherty claystone, represented by chalcedonic casts. 



Slide No. 611. — Agglomerate-matrix from Cleary's Hill, near 

 Tamworth. The base is a mixture of cryptocrystalline felsite, with 

 phenocrysts of felspar, augite, and calcite, packed so closely together 

 in it as to preclude the application of the term ' porphyritic ' 

 to the structure of the rock. It has rather the appearance of an 

 aggregate of much fractured and corroded macroscopic crystals, with 

 interstitial felsitic material, and here and there small fragments 

 of microcrystalline felsite almost blended at their margins with the 

 base, and larger pebble-like lumps of the porphyritic andesite 

 described in slide No. 621 (p. 36). 



A little pyrites and titaniferous iron (possibly some of this is 



d2 



