^^^' 55*] 0^ PALiEOZOIC EADIOLAKIAIS" KOCKS IN" N". S. WALES. 21 



about thirteen beds of thin lenticular limestones, each from 6 to 

 over 12 inches thick, the total thickness of the intermediate strata 

 being approximately 1000 feet. Several of these limestones are 

 largely formed of radiolarian tests, or their comminuted and altered 

 remains, but some are so altered as to have had almost all traces 

 of the radiolaria obliterated. That originally they were largely 

 formed of radiolaria may be inferred from their close resemblance 

 to similar beds in the same series, from obscure spherical casts 

 contained in them of the same size as those of undoubted radio- 

 larian casts in the adjoining rocks, and from the abundance of casts 

 of radiolaria in the cherts and claystones with which the thin 

 limestones are interstratified. 



The black cherts contain very numerous casts of radiolaria, at 

 the rate, approximately, of about one million to the cubic inch. As, 

 however, this part of the section cannot be so satisfactorily worked 

 out as in the area where, according to our interpretation of the 

 section, the beds are repeated by the great fault which runs 

 through Tamworth Common, further description may be reserved 

 until the Tamworth Common section is discussed. The beds of 

 radiolarian limestone are lettered H to T, inclusive, along the 

 line of section (PI. III). All these limestones agree in general 

 characteristics. They are dark bluish-grey at some depth from the 

 surface, but weather into a soft, brownish, earthy material re- 

 sembling ' rotten -stone ' or Bath brick, and can be readily crumbled 

 between one's fingers. With the aid of a pocket-lens radiolarian 

 tests may be seen in abundance in some of the weathered crusts. 



The total thickness of strata represented from the top of the 

 garnetiferous limestone to the radiolarian limestone-bed marked H 

 is about 1400 feet. Between H and the next radiolarian limestone- 

 bed, marked G, there is a thickness of about 2750 feet of cherty 

 claystones and tuff. Every specimen so far examined shows that 

 the claystones are largely formed of radiolaria. Possibly some 

 lenticular beds of radiolarian limestone in this part of the section 

 may have escaped our notice. The maximum thickness of G is 

 about 1 foot. It is lenticular and intermittent, dipping 48° south- 

 west. 



A thickness of about 50 feet of cherty claystones separates 

 the limestone-bed G from that next above it, F. Indistinct plant- 

 remains, together with Lepidodendron austrcde, were discovered 

 by us in a bed 3 inches thick in the claystones. The bed F is 

 similar in nature to G, and is from 6 to 12 inches thick. 



Next above F comes a thickness of 245 feet of claystones, 

 succeeded by a bed of tuff, in which numerous well-preserved 

 specimens of Lejndodendrooi austrcde can be seen in situ. These 

 were first noticed by Mr. F. Blatchford (who assisted us in the 

 examination of this district) in some talus formed of fallen 

 fragments of the tuff. Such specimens are generally within an 

 inch or so of fragments of the radiolarian claystone entangled in the 

 tuff. In some cases impressions of L. ausfrale can be seen in 

 the entangled claystone-fragment ; in others the cast is completely 



