66 Geological Society 



2. "Notes on Pleurodon affinis, sp. ined., Agassiz, and Description 

 of three spines of Cestracionts from the Lower Coal-measures." By 

 J. W. Davis, Esq., E.G.S. 



3. " On the Distribution of Boulders by other Agencies than that 

 of Icebergs." By C. E. Austin, Esq., C.E., E.G.S. 



The author is of opinion that if boulders had been distributed by 

 floating ice they should now be accumulated " in certain parallel and 

 quasi- concentric lines." This he does not find to be the case in 

 Sweden and North Eussia, where the distribution is irregular. 

 Erom the mode of distribution he infers that the boulders must have 

 been uniformly distributed in the ice blocks, whereas they ought to 

 have been most abundant at the base. The boulders are not con- 

 nected with existing ravines, and the author does not see how ice 

 can move on a plain. He has never seen a glacier-moraine, but 

 thinks that these boulders are not like the blocks in moraines. In 

 Siberia, Portugal, and Bio Janeiro the author has seen solid nuclei 

 in decomposed granite. Such boulders, as he notices, may be left 

 after decomposition of a once flowing molten mass, of which they 

 have formed a part or in which they have been entangled. 



December 4. — Henry Clifton Sorby, Esq., E.R.S., President, 

 in the Chair. 

 The following communications were read : — 



1. "On some Mica-Traps from the Kendal and Sedbergh Dis- 

 tricts." By Prof. T. G. Bonney, M.A., E.R.S., E.G.S., and E. T. 

 S. Houghton, Esq., B.A. ■ 



The rocks described by the authors are mapped by the Geo- 

 logical Survey on quarter sheets 98 N.E., 98 S.E., and 97 N.W., 

 and in parts briefly mentioned in the accompanying memoirs, 

 under the generic name mica-trap. Seventeen examples are de- 

 scribed macroscopically and microscopically ; and of eight, chemical 

 analyses are given. It appears better to call one a porphyrite and 

 two diorites (micaceous varieties). The remainder are all cha- 

 racterized by abundance of mica (biotite). Augite also appears to 

 have been generally a constituent ; but it has almost invariably been 

 replaced by secondary products — calcite, dolomite, viridite, &c. Three 

 are crystalline in structure ; one of these is named minette, the 

 others kersantite. The remaining eleven show a microcrystalline or 

 cryptocrystalline base. It is proposed to call eight of them minette- 

 felsite, the rest kersantite -porphyrite. These rocks commonly occur 

 in rather narrow dykes ; they are intrusive in Silurian strata, and, 

 in the authors' opinion, are undoubtedly true igneous rocks. 



2. " Pleistocene Notes on the Cornish Coast near Padstow." By 

 W. A. E. ITssher, Esq., E.G.S. 



In this paper the author described certain deposits seen in a small 

 bay near St. Enodock's chapel, and known as Daymer Bay, and in 

 section at Green way cliffs. The former included a portion of raised 

 beach, and a reef of consolidated old beach and a peaty deposit below 



