520 Notices of Memoirs — J. Rhodes — Silicified Plants. 



in addition to the oolite grains, fragments of molluscan shells and 

 echinoderms, and foraminifera, in a finely granular matrix formed 

 of calcite. He observed that the central portions of some of the 

 oolite grains were formed of a nearly isotropic brown substance in 

 which the typical concentric structure of the oolite grains was well 

 preserved. This substance was no doubt phosphatic. 



III. — Note on the Discovery of a Silicified Plant Seam 



BENEATH THE MiLLSTONE GrIT OF SwARTH FeLL, WeST RiDING 



of Yorkshire. By John Rhodes, of the Geological Survey.^ 



BY kind permission of the British Association Committee on 

 Carboniferous Zones I am enabled to record the discovery of 

 a silicified plant seam beneath the Millstone Grit at Swarth Fell, 

 and two miles north-west of Hawes Junction. 



The exact geological position of the overlying strata is doubtful, 

 but apparently they occupy the horizon of the grindstone or ganister 

 of the district. 



At this particular place, however, the grindstone or ganister is 

 absent, and its place is taken by flaggy silicious limestones with 

 marine shells and by a bed of highly silicious grit with plant remains, 

 the latter resting more or less directly on the silicified plant seam. 



Chert occurs, probably as lenticles in the uneven surface of the 

 seam, and contains a mass of detached silicious sponge spicules, 

 apparently rod-like bodies, which may belong to the anchoring ropes 

 of hexactinellid sponges. In the same chert are included fragments 

 of silicified plant remains beautifully preserved. 



In the plant seam included pebbles of silicious grit occur, which 

 contain a few spicules similar to those in the chert, and also 

 plant remains. The plant seam rests on a layer of silicified shale 

 containing a few fragmentary sponge spicules, mostly rod-like forms, 

 one piece belonging to an hexactinellid sponge. The beds below 

 are more or less rotted clay shales with ironstone nodules. 



I am indebted to Dr. G. J. Hinde for notes on the sponge remains 

 directly associated with the plant seam. The plants have not been 

 determined, but have been placed in the hands of R. Kidston, Esq., 

 F.R.S.E., F.G.S., Stirling. 



IV. — The Copper-bearing Rocks of South Australia. By 

 F. P. Mennell.1 



THE author drew attention to the fact that the copper ores of 

 Yorke's Peninsula in South Australia were the first metallic 

 minerals worked on the Australian continent. They occurred in 

 rocks of Archeean age, which at Moonta and Wallaroo had been 

 subjected to crushing and shearing to such an extent that they 

 presented but few traces of their original structures, except in the 

 case of a diorite at Wallaroo, which was of a typically plutonic 

 character. Most of the rocks were mylonites, and in some instances 



1 Read before the British Association, Section C (Geology), Glasgow, Sept., 1901. 



