[ 160 ] 

 XT. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxxii. p. 528.] 



November Sth, 1916.— Dr. Alfred Harker, F.R.S., President, 

 in the Chair. 



nnHE following communication was read : — 



^Aulina rotiformis, gen. efc sp. nov., Phillipsastrcea hennahi 

 (Lonsdale), and the Genus Orionastrcea.' By Stanley Smith, 

 B.A., D.Sc, F.G.S. 



Mr. J. W. Jackson exhibited a number of facetted pebbles from 

 Pendleton (Lancashire), and stated that nearly 200 of these had 

 been collected during the last six months from near the top of a 

 section of current-bedded and faulted Glacial Sand and Gravel at 

 an altitude of about 200 feet O.D. 



The pebbles occur in situ some 2 or 3 feet below the capping of 

 darker subsoil, which contains cores and flakes of flint, including 

 pigmies. They consist of slate, granites (Eskdale and Shap), 

 Ennerdale granophyre, Borrowdale volcanic tuffs, porphyries, 

 quartzites, Millstone Grit, sandstones, Chalk flints, Carboniferous 

 chert, and other rocks. 



The largest facetted pebble measures 11| X 8£ inches, and is 

 7 inches high ; the smallest is only half an inch in diameter. 



The facets are generally concave, grooved, or fluted. They vary 

 in number : some stones have one facet only, others two or more. 

 One stone with a flat top shows five incipient facets. On some 

 the grooving is of the nature of parallel series of elongated pits. 



Differentiation, according to varying hardness and composition, 

 is well displayed on the granites, porphyries, grits, etc., where the 

 weaker constituents have been strongly eroded, leaving the stones 

 with an irregularly pitted surface. 



The production of facets by splitting along joint-planes is seen 

 on some examples of sandstone ; but the facet thus formed has been 

 modified by wind-action. 



A few pebbles occurred in the sand completely inverted, and 

 some show distinct facetting on both sides. 



Of examples orientated in situ, the facets faced north-westwards, 

 westwards, and south-westwards — the directions of the present 

 prevailing winds. 



All the pebbles are of Glacial origin, but the facetting may be 

 relatively quite recent. The upper part of the sands where they 

 occur may be the result of redistribution by wind before a soil-cap 

 began to form. 



