Geological Society of London. 381 



and we would recommend a reader interested in the matter to turn 

 instead for information to Mr. H. Blanford's little book and to the 

 geological chapters published, or in course of publication, in the 

 Government of India's Gazetteers for each of the Presidencies, 

 wherein condensed accounts of the local geological features will be 

 found. W. 



REPORTS -A-ZLsTID IPROCIEIEIDIIDsra-S. 



Geological Society of London. — May 26th, 1875. — John Evans, 

 Esq., V.P.E.S., President, in the Chair. — The following communi- 

 cations were read : — 



1. " On some Peculiarities in the Microscopic Structure of Fel- 

 spars." By Frank Eutley, Esq., F.G.S. 



The observations recorded in this paper related mainly to some 

 exceptional features in the striation of felspars from various localities, 

 involving a consideration of the extent to which dependence may be 

 placed on the discrimination of monoclinic and triclinic felspars by 

 the methods usually recognized in ordinary microscopic research. 

 Some other peculiar structural features were likewise noticed, and 

 the effects which might' be produced on polarized light by the over- 

 lap of twin lamellae in thin sections of felspars, when cut obliquely 

 to the planes of twinning, were also considered. 



The paper terminated with a list of conclusions deduced from the 

 observations recorded. These conclusions mostly related to matters 

 of detail ; but the general inference drawn by the author was that 

 the present method of discriminating between monoclinic and tri- 

 clinic felspars by ordinary microscopic examination answers sufficiently 

 well for general purposes, although it is often inadequate for the 

 determination of doubtful examples, and that such examples are 

 of more frequent occurrence than one would at first be led to suspect. 



2. " On the Lias about Eadstock." By Ealph Tate, Esq., A.L.S., 

 F.G.S. 



In this paper the author described several sections in the Lias of the 

 neighbourhood of Eadstock in Somersetshire, with special reference 

 to their palaeontological contents, and to the question of the division 

 of the Lias into zones in accordance with the species of Ammonites 

 occurring in different parts of the series. He maintained that 

 although the Lower Lias in this district only attains a thickness 

 of 24 feet, this is due to poverty of sediment ; and that whilst by 

 this means the zones are compressed, and the species of Am- 

 monites brought almost into juxtaposition, the succession of Am- 

 monite-life is as regular in the Eadstock Lias as in the most typical 

 districts. Much of the opposition to the doctrine of zoological zones 

 he ascribed to erroneous discrimination of species. The paper 

 included tables of sections and lists of fossils, with the arguments 

 founded upon them, in support of the above opinion. A few new 

 species were described under the names of Trochus solitarius, 

 Cryptcena affinis, Cardita consimilis, and Cardinia rugidosa. 



