228 Geological Society : — 



commonly found entire are usually of small size, and of a form cal- 

 culated to resist pressure, — such as Turritella communis, Trophon 

 clathratus, and Mangelia turricula. Fusus antiquus and Buccinum 

 undatum are generally represented only by worn fragments of the 

 columella; and Gyprina islandica is. always found in fragments. 

 The author thought that the association of the various species dis- 

 tributed without order through the clays shows that they could not 

 have lived together on the same bottom, but that they must have 

 been to a great extent transported. He contended that the ad- 

 mixture of shells in the Boulder-clay was due to the tendency of the 

 sea to throw up its contents on the beach, whence changing cur- 

 rents and floating ice might again remove them, and to the oscilla- 

 tions of the land bringing all the beds at one time or another within 

 reach of marine erosive action. He maintained that it is in the 

 distribution of land and sea at the period of deposition of the Lan- 

 cashire deposits, and not in astronomical causes, that we must seek 

 the explanation of the climate of that period, the conditions of which 

 he endeavoured to explain by a consideration of the proportions of 

 the species and the natural habitats of the shells found in the drifts. 



3. " Note on a deposit of Middle Pleistocene Gravel near Ley- 

 land, Lancashire." By R. D. Darbishire, Esq., F.G.S. 



The bed of gravel, about 40 feet thick, and about 240 feet above 

 the level of the sea, is covered by yellow brick clay, and overlies an 

 untried bed of fine sea-sand. The shells and fragmens occur chiefly 

 at the base of the gravel. 



The most noticeable shells in this list of forty-two species, col- 

 lected by Miss M. H. Earington, were Pcmopcea norvegica, Mactra 

 glauca, Cytherea chione, Cardium rusticum, Fusus propinquus, and 

 Fusus antiquus, var. contrarius. One specimen of a Fusus, doubt- 

 fully identified as F. Fabmcii (craticulatus), had occurred. 



The group was by no means characteristically Arctic or Glacial. 

 It represented most nearly the AVexford lists, especially in present- 

 ing the reversed Fusus, and might be regarded as connecting those 

 beds with the Macclesfield drifts, also containing a Celtic assortment, 

 with Cytherea chione and Cardium rusticum. 



The author considered the Leyland deposit, like those on the west 

 of the Derbyshire hills, to be more probably littoral and truly cli- 

 matic than that of the Liverpool clays, the subject of Mr. Beade's 

 Paper, and hazarded the conjecture that the latter were sea-bottom 

 beds, into which, during some process of degradation and redistri- 

 bution, the specimens found and enumerated by Mr. Reade had been 

 carried down from the former more ancient retreating coast-lines. 



December 3rd, 1873.— Joseph Prestwich, Esq., E.R.S., 

 Vice-President, in the Chair. 



The following communications were read : — 

 1. " Notes on the Structure sometimes developed in Chalk." By 

 H. George Eordham, Esq., F.G.S. 



After referring to Mr. Mortimer's paper on the same subject (see 



