J. Lamplugh — Marine Shells in Boulder-clay. 509 



lY.— On the Occurrence of Marine Shells in the Boulder-clay 



AT Bridlington and elsewhere on the Yorkshire Coast. 



By J. Lamplugh, 



of Bridlington Quay. 



"With Notes by F. A. Bedwell, Esq., M.A., F.G.S. 



IN 1874, "whilst searching in the Boulder-clays south of Brid- 

 lington, on the Yorkshire Coast, for transported fossils, I was 

 greatly surprised to find a few water- worn fragments of shells 

 dispersed through the clay at the base of the cliff, inasmuch as all 

 the writers on this subject agree in assigning to the Yorkshire Clays 

 " no contemporaneous shells whatever," ' that is to say, no shells 

 actually coeval with the deposition of the clay. 



From that time I carefully searched for, and preserved all these 

 fragments, obtaining, however, only a very limited number of 

 species ; until a short time ago, when I had the good fortune to 

 witness a small exposure on the south shore, close to the town, of a 

 bed of clay, which is usually covered deeply with sand and shingle, 

 so exposed, and is very different from the Purple clay of the ad- 

 joining cliff. In this clay, shell-fragments were more plentiful, and 

 perfect, and I obtained from it the remains of about a dozen species ; 

 and by recent and more extensive exposures, have been enabled to 

 raise this number to about thirty species. 



As these shelly clays are evidently very closely connected with 

 the "so-called Bridlington Crag,"^ a deposit which is only partially 

 understood, I doubt not that a detailed account of them will be 

 found to possess interest. 



The two distinct masses into which the Boulder-clay in this 

 neighbourhood is divided, are marked, not only by their lithological 

 characters, into ' Blue ' and ' Purple,' but also by the presence 

 between them of a thin bed of laminated ' snuff- brown ' clay, 

 which for the most part contains no pebbles whatever, being very 

 pure and soft, and remarkably tenacious. 



This snufi-coloured clay seems to be a strictly local deposit, 

 occurring only in Bridlington Bay. It appears both to the north 

 and south of the town. To the north it may be traced at intervals 

 along the base of the wasting clifi", for a few hundred yards north- 

 ward from beneath the lime-kiln. To the south it is at present well 

 exposed on the South Sands ^ between high and low-water marks, for 

 about three-quarters of a mile, and it then either thins out or sinks 

 beneath the sea, a point which can only be ascertained by careful 

 examination of well-borings, etc., further south ; but I am inclined 

 to think that it will not be found to extend further than the place 

 above indicated, viz. halfway between Auburn and Bridlington. 



Its thickness, which is evidently very variable, is 40 inches at the 



^ Phillips' Geology of Yorkshire, 3rd ed. p. 164; "Wood and Eome, Quart. 

 Journ. Gaol. Soc. vol. xxiv. p. 147. 



~ For some account of the Bridlington Crag see a paper by Dr. S. P. "Woodward, 

 F.G.S., Geol. Mag. 1864, Vol. I. p. 49. 



^ The beach to the north of Bridlington is locally known as the " North Sands, 

 and that to the south of the town as the " South Sand?." 



