Reports and Proceedings — Geological Society of London. 91 



matter. We recognize throughout the vigorous original touches of 

 the accomplished biologist, aud if, in his treatment of some of the 

 problems of speculative geology, the results seem not quite so 

 satisfactory, the faults, if there be any, are perhaps less with the 

 author than in the nature of the subject. 



The volume is well got up, and usefully illustrated with maps 

 throughout. W. H. H. 



laZEZPOIiTS JLH^rZD ^ieOG:B:BIDTITC3-S. 



Geological Society of London. 

 I.— Dec. 15, 1880.— Robert Etheridge, Esq., P.R.S., President, in 

 the Chair. — The following communications were read : — • 



1. " On the Constitution and History of Grits and Sandstones." 

 By John Arthur Phillips, Esq., E.G.S. 



In the first part of this paper the author described the micro- 

 scopic and chemical structure of a large series of grits, sandstones, 

 and, in some cases, quartzites, of various geological ages, noticing 

 finally several sands of more or less recent date. The cementing 

 material in the harder varieties is commonly, to a large extent, 

 siliceous. The grains vary considerably in form and in the nature 

 of their inclosures, cavities of various kinds and minute crystals of 

 schorl or rutile not being rare. The author drew attention to the 

 evidence of the deposition of secondary quartz upon the original 

 grains, so as to continue its crystal structure, which sometimes 

 exhibits externally a crystal form. This is frequently observable 

 in sandstone of Carboniferous, Permian, and Triassic age. Felspar 

 grains are not unfrequently present, with scales of mica and minute 

 chlorite and epidote. Chemical analyses of some varieties were also 

 given. The author then considered the effect of flowing water 

 upon transported particles of sand or gravel. It results from his 

 investigations that fragments of quartz or schorl less than -gV' in 

 diameter retain their angularity for a very long period indeed, 

 remaining, under ordinary circumstances, unrounded ; but they are 

 much more rapidly rounded by the action of wind. It is thus 

 probable that rounded grains of this kind in some of the older rocks, 

 as, for example, certain of the Triassic sandstones, may be the result 

 of iEolian action. 



2. " On a New Species of Trigonia from the Purbeck Beds of the 

 Vale of Wardour." By E. Etheridge, Esq., F.R.S., President. With 

 a Note on the Stratigraphical Position of the Fossil by the Rev. W. 

 K. Andrews. 



In this paper the author described a species of Trigonia discovered 

 by the Rev. W. R. Andrews in the " Cinder-bed " of the Middle 

 Purbeck series in the Vale of Wardour. Tiie specimens were found 

 in the railway-cutting one mile west of Dintou station. The shell 

 was referred to D'Orbigny's section " Glabrte" of the genus Trigonia, 

 and named Trigonia densinoda. In its ornamentation it closely 

 resembles T. tenuitexta, Lye, of the Portland Oolite ; but is more 

 depressed and lengthened posteriorly, and destitute of the ante- 



