PLIOCENE PERIOD W ENGIAJfD* 515 



the same error as to the time of the great submergence I attributed 

 the succession of that clay to the Chalky to its having been formed 

 by the extrusion of moraine from the same ice as that of the Chalky 

 Clay, under an increased submergence of the country, which had 

 caused this ice to recede from the Chalk Wold, and so put an end to 

 the Chalky Clay. This view of the cause of the succession, and of 

 its attendant conditions, I also, as the preceding pages show, do not 

 now entertain. 



Very shortly after this paper, the late Prof. Harkuess entered 

 very elaborately into the subject of the transit of the Shap blocks*, 

 contending for their transit by floating ice, when the Pennine stood 

 more than 1500 feet below its present level. On the other hand 

 there are geologistsf who have entertained the opinion that this 

 transit was effected not by floating but by land ice, a view that, as 

 appears in the sequel, I have now seen reason to adopt. All those 

 geologists who have studied the glacial phenomena of the North- 

 west of England appear to have thought that the great submergence 

 indicated by the Moel Tryf aen and Macclesfield shell-gravels followed 

 the glaciation of that part of England, and the formation of the 

 Lower Boulder-clay of Lancashire and Cumberland (with which, in 

 my view, the Purple Clay of Yorkshire is identical), and that with 

 this submergence the glacial conditions passed away, except so far as 

 the Upper Poulder-clay of that region indicated their renewal. 

 My own view also up to the time when, three years ago, I first tried 

 to grapple with the subject of this memoir by examining and col- 

 lating analytically all the evidence concerning the newer Pliocene 

 formations which I had, during many years' work upon them in the 

 field, collected, was the same ; and the principal thing which in- 

 fluenced me in this opinion was the character of the molluscan 

 fauna found in these formations. It was not so much the remains 

 found in the seam near the top of c that influenced me (for, as already 

 explained, these, I think, have been ploughed out of a sea-bottom 

 which began to form during the earlier part of the long period of 

 Stage IL), but those which occur at Bridlington, and more especially 

 those of the seam of sand in, but near the top of, the Basement 

 clay of Holderness at Dimlington, where its junction with the Purple 

 Clay which overlies it is displayed in the cliff. 



This seam was detected by a party of geologists consisting of Sir 

 Charles Lyell, Mr. Leonard Lyell, Prof. T. M. Hughes, and Mr. 

 Eome ; and a description of it was sent to me by Sir Charles Lyell 

 with the molluscan remains which they extracted. These remains, 

 especially those of the Nucula, were, many of them, broken, though 

 freshly fractured and unworn ; but the written description sent me 

 with them was that they were taken from a seam of dark sand lite- 

 rally packed luith perfect specimens of Nucula Cohholdice, which 

 seemed to be double ; and this was certainly the condition of one of 

 the bivalves (Astarte compressa) which was sent to me. 



The Bridlington bed has been long known, and was described by 



. * Quart. Journ. vol. xxAri,. p. 517. t G-oodchildj ibid. yoL xxxi. p. 98. 



