Geological Society of London. 43 



into which, during some process of degradation and redistribution, 

 the specimens found and enumerated by Mr. Eeade had been carried 

 down from the former more ancient retreating coast-lines. 



Discussion. — Mr. Darbishire was not prepared to accept the view of the shells 

 in the r'rift having existed on the spots where now found. He thought rather that 

 the fragmentary remains might have been derived from the destruction of earher 

 beds deposited under somewhat different conditions. The occurrence at Wexford 

 of nearly similar beds to those at Leyland pointed to a great destruction of an old 

 sea-shore. 



Mr. Gwyn Jeffreys thought that all the shells found in these Lancashire beds 

 were just such as might have been thrown up on the shore, though the matrix in 

 which some of them are found is not sandy. The TrophoJi discovered was T. 

 truncaUis, and not T. clathratus. Neither was he quite satisfied that Miss Faring- 

 ton's Fusus was really F. craficulatics. The occurrence of Fusus antiqims, monstr. 

 contrarius, did not surprise him, though that of Mactra glauca was very remark- 

 able. He did not believe in the retiring or voluntary migration of mollusca, though 

 they might be transported by currents or driven away by want of food. He did 

 not regard any of the shells as truly Arctic, and doubted whether any of them 

 afforded clear evidence of climatal conditions. 



Mr. Prestwich remarked on the progress which had been made in our knowledge 

 of these shells since Sir P. Egerton had first called attention to the drift in which 

 they occur. The number of perfect specimens from Leyland was, he thought, 

 very striking. He had some difficulty in following Mr. Reade into the large theo- 

 retical questions into which he had entered, but pointed out that the striation of 

 the surface of the country was significant of a period of intense cold, for which any 

 alteration in the arrangement and proportions of land and water could hardly 

 account. But in the overlying Boulder-clay the fragments of shells were all of 

 species still existing in the neighbouring seas of the present day, and he did not 

 think that at the time of its deposit the climate was of necessity intensely cold. 



Prof. Hughes did not think that the deposits were in any way immediately con- 

 nected with the Boulder-clay, to which they were long subsequent. He rather 

 correlated them with the Hessle and Kelsey beds of the East coast. The deposits 

 might in many cases have been formed on the shore of a sea which was eroding a 

 cliff of Boulder-clay ; and by this means there would be an admixture of the more 

 recent shells with the redeposited boulders from the older clay. He submitted 

 that the shells belonged to an age succeeding the true Glacial period. In the higher 

 deposits there were still some traces of the more Arctic forms, while a more southern 

 facies came over the fauna of the lower beds. 



Mr. Charlesworth observed on the possibility of the transport of shells in the 

 stomach of fishes. As to the comminuted condition of Cyprina Islandica, he re- 

 marked that in the Crag beds these shells are nearly always much cracked, even 

 when delicate shells in the neighbourhood are perfect. 



The Chairman was glad that the old view as to the successive elevations and 

 submergences during the Glacial period was not likely to be disturbed. As to the 

 physical causes which conduced to the extreme cold, he did not undervalue the 

 changes in physical geography ; but if the astronomical causes, the existence of 

 which seemed now to be fairly established, would have produced the effects, he 

 did not see why they should be ignored even if the geographical causes might 

 suffice. These latter seemed to be at best theoretical, whereas the former seemed 

 mathematically necessary. He was not inclined to detach the shells from the clay, 

 and thought that during the time of their deposit there were still glaciers on the 

 higher points of the land. He did not agree with Prof. Hughes in regarding the 

 beds with striated pebbles in the Vale of Clwyd as Post-glacial, and could not be- 

 lieve that in the case of the reconstruction of the beds the striae could be preserved 

 and the pebbles not become smooth. 



Mr. Reade, in reply, stated that his observations were intended to apply merely 

 to the conditions under which the beds containing the shells had been deposited, 

 and not to the period of extreme cold, for which he was quite willing to admit the 

 potency of astronomical causes. He agreed with the Chairman in regarding the 

 clay as a real Boulder-clay, the pebbles in it being for the most part scratched. 



