G. W. Lamplugh — The Bridlington Shell-led, etc. 543 



separated by about three incbes, probably by the shearing of the 

 whole mass of the clay under pressure. 



I have not seen a representative of the chalky clay above the 

 shelly clay at Bridlington, though from the already-quoted descrip- 

 tions given by Prof. Phillips and Dr. Sorby of that part of the cliff 

 now concealed, it is possible that such may exist. 



As the shelly clay reaches low-water mark at Dimlington and 

 Bridlington, 1 can give no account of its thickness, nor of the 

 underlying beds. 



Origin and Formation of the Beds. — As there are points con- 

 nected with these beds that I do not yet understand, it would be 

 useless for me to attempt to explain their origin. Thus, one point 

 — and this bears strongly on the origin of the shelly patches — 

 is the peculiarly restricted range of the shells, and the difference 

 between the fauna of patches almost adjoining. For instance, at 

 Dimlington nowhere did I find Dentalium striolatmn, save in one 

 small patch, where, from a mere handful of clayey sand, I obtained 

 the remains of over a dozen individuals. In another patch I found 

 Natica affinis, — in another, a few fragments of Niicula Cobboldice, — 

 in another, Pecten Islandicus ; and so on ; in each case associated 

 with a few forms such as Tellina baltJiica, Saxicava rugosa, Astarte 

 horealis, and A. sulcata, var. elliptica, which occurred in varying 

 proportions nearly everywhere. It was the same at Bridlington. 

 There, in the largest mass, several shells were found which were 

 not present in the smaller patches ; and in one of the latter 

 Pleurotoma turricula was the most abundant shell, and was peculiar 

 to it. Thus, again, some years ago Mr. Bedwell obtained Cijprina 

 Islandica with valves united, though much crushed, from an ex- 

 posure on the beach near the original bed, but nowhere have I 

 seen this shell in place, though fragments of it, derived from some 

 such bed, are plentiful in the Boulder-clay. Tellina halthica, too, 

 is far more plentiful in the Boulder-clay than in any of the shell- 

 patches I have seen. 



Now this, coupled with their diverse composition, shows that 

 the masses have been brought together from different depths and 

 localities, — a result which does not seem to me to be exactly what 

 we should expect to be brought about either by land or floating ice. 

 It has, perhaps, been produced by a combination of both, since, I 

 suppose, an ice-sheet advancing over a sea-bottom would necessarily 

 throw out before it a thin fringe of bergs, whose pioneer work on 

 unbroken ground even the passage of the main mass might not 

 entirely obliterate. Or, it may have been caused by the passage of 

 the eroding agent over the edges of an older series of variable beds ; 

 but much of the evidence discountenances this view. 



At any rate, I think the coarse sand was the true old sea-bottom 

 on which the shells lived ; and that this sea-bottom was afterwards 

 covered by a thick deposit of glacial mud ; and then the whole 

 subjected to some disturbing force, — ice in some form no doubt, — 

 which removed it piecemeal ; perhaps in frozen masses. 



In the Appendices I give full lists of the shells. 



