Correspondence — Mr. C. 8. Wilkinson. 



287 



the author has obtained many other organisms from this clay, and 

 especially a large number of Foraniinifera now in the hands of Prof. 

 Karrer of Vienna. He estimates the total number of determinable 

 species belonging to various classes at over 200. 



In treating of his special subjects the author adopts the principles 

 of classification laid down by Hincks, Smitt, and other recent writers 

 on living Bryozoa, which he regards as preferable in themselves, and 

 also as facilitating the comparison of fossil with recent forms. 



coiaiaiKisiPOi^iDiBisrcs. 



GLACIAL BOULDERS 



IN SECONDARY DEPOSITS, 

 SOUTH WALES. 



SIDNEY, NEW 



Mr. C. S. Wilkinson, F.G.S., Government Geologist, Department of 

 Mines, Sydney, N.S. Wales, referring to the occurrence of Glacial 

 boulders in the "Hawkesbury Sei'ies," ^ writes to Mr.E. Etheridge, jun., 

 under date lOth February, 1881 : — "Here we have huge and small 

 angular masses of soft shales embedded in pebble conglomerates and 

 false-bedded sandstones. With these sandstones (Hawkesbury) are 

 interstratified argillaceous shales, and the boulders are of the same 

 material and contain the same fossils. It seems that during the 

 deposition of the Hawkesbury Series, the rapid and changing currents 

 which deposited the false-bedded sandstones, were at intervals suc- 

 ceeded by quiet waters, from which the mud forming the shales 

 settled down, probably during winter-time, when ground-ice formed. 

 Spring-time following, the ice broke up, and drifting about broke 

 up some of the newly-formed shales, and mingled the shale frag- 

 ments with pebbles and sand brought by currents from the shores. 

 The shale boulders are always found just above, or not far from the 

 undisturbed shale-beds, thus : — 





In the sandstones just above the bed with angular blocks (J.), are (B) 

 small rolled flattish pieces of the same shale, the longer diameter 

 inclined in one position, showing the direction of the transporting 

 currents at the time ; some of the angular masses are curved, 

 showing that they must have been in a soft condition, when torn 

 up from the underlying shales. The principal fossils found in these 

 are fragments of Plants — I'hyllotlieca, Thinnfeldia, Odontopteroides ; 

 Fishes — Palceoniscus, Oheirolepis granulaius, Myriolepis ClarTcii, and 

 another, which appears to be new." 



^ Lower Mesozoic. 



