562 GREAT SERPENTINE-BELT OF NEW SOUTH WALES, V., 



character. Little veins, that break across the stratification of 

 the claystones, project outwards from the otherwise apparently 

 interbedded tuff. It was first pointed out to the writer by Mr. 

 Aurousseau, B.Sc, that one of the bands of igneous rock about 

 a yard in width, tliough no difi'erent to the naked eye froin the 

 normal fine-grained tuff, was really a massive and thoroughly 

 albitised spilitic dolerite. Though a number of other fine-grained 

 igneous rocks in the Upper Middle Devonian series have since 

 been subjected to microscopic examination, this is the only 

 massive rock yet found in that series. It occurs in the road, 

 metal-quarry, at the southern end of the ridge beside the creek. 

 In this quarry, and in that adjacent to it, are the most accessible 

 examples of the interbedded lenticular radiolarian limestones. 

 They occur up to six feet in length, and nearly two feet in width, 

 but the majority are smaller than this. Some sign may at times 

 be seen of a structure that has been most clearly observed in a 

 limestone-lens at Nundle, namely, that the same lines of strati- 

 fication as are in the adjacent mudstone continue right through 

 the limestone, but are much further apart here than in the clay- 

 stones. The bedding-planes of the claystones, therefore, appear 

 to bend inwards at either end of the limestone-lens, and thus to 

 follow its outline (see Text-fig. 3). Presumably the lens was 



Fig.3. — Lenticle of Radiolarian Limestone. 



formed by segregation of lime in the soft unconsolidated muds, 

 which have subsequently been much more closely compacted by 

 pressure of ot^erlying sediment, etc., than the solid lens which 

 had formed in them. 



Below the limestone at the southern end of its outcrop, is a 

 small anticline noted by the previous authors. It seems, how- 



