516 J. Lamplugh — Marine Shells in Boulder-clay , 



fragments of marine shells in the ' Purple ' clay (which, as I think, 

 evidently came from the landward), viz. to their having been 

 derived from the lower beds; the fact already dwelt upon of the 

 absence of shells from the sands included in the ' Purple ' clay being 

 strong presumptive evidence that they were not truly contempor- 

 aneous. 



It is evident that the materials forming the Purple clay have been 

 dropped through waters of some depth on to the surface of the 

 laminated clay, as the nature of the latter deposit would otherwise 

 have caused it to be readily swept away. As it is, I witnessed one 

 exposure of it on the South Beach which showed remarkable con- 

 tortions, and to the north of the town, at the point already referred 

 to, beneath Sand Cottage, it is altogether absent for a short space, 

 the 'Purple' there resting directly upon the 'Basement' clay. 

 Probably the glacier, after crossing the chalk hills which form the 

 boundary of Holderness to the north and west, would reach deeper 

 waters, and there, slowly melting, drop its burden quietly through 

 the waters of the sea. 



In conclusion, I need scarcely add that, though in the present state 

 of our knowledge of the subject this seems to me to be the best way of 

 accounting for the presence of shells in the Yorkshire Boulder-clays, 

 still I anticipate that further examinations will make it necessary 

 for me to modify these views ; for much earnest work and much 

 patient study has yet to be done before the origin of these clays is 

 really settled ; and if, in the mean time, I have added but a little to 

 the slowly accumulating mass of information on the subject, I shall 

 feel richly rewarded. 



List of Shells from the Upper Part of the ' Basement ' Clay (forming 

 PART OF ' Bridlington Crag ' Deposit) at Bridlington, as exposed in 

 THE South Sands. Examined and partly determined by Dr. H. 

 Woodward, F.E.S. 



Those which occur also in the ' Purple ' clay are marked with an 

 asterisk. Those marked with a dagger are additional species 

 obtained by me from the lower clay at Filey and Cayton. Should 

 this bed prove to be merely a sub-division of the ' Purple ' clay (the 

 opinion held by Messrs. Wood and Eome), the shells thus marked 

 will, of course, go to increase the list of those already obtained from 

 the ' Purple ' clay. (The prefixed c, denotes the shells which are 

 common.) 



Pecten opercidaris, Linn. 

 Nucula Cobboldiee, Leathes. 

 *Leda rostrata, Flem. 

 Peciunculus glycmieris, Linn. 

 Cardium edule, Linn. 



,, Parkin soni, Sby. ? 

 ,, Grmnlandicwn, Chejon,? 

 C *Cyprina Islatidica, Linn. 

 *Astarte elliptica, Brown. 

 ,, cowpressn, Montagu, 

 c* ,, borealis,CheiaQ.. 

 t „ Sp. 



Venus (?) 



c *TelUna solidula, Pulteney. 

 c * „ ohliqua, Sby. 

 Mya truncnta ? Linn. 

 t ,, arenaria^ Linn. 

 ^Lidraria elliptica. Lam. 

 Saxicava rvgosa, Linn. 

 Pholas crispata, Linn. 

 *Dentalium entale, Linn. 

 Trochus siziphimts, Linn. ? 

 Bucchmm midaliim, Linn. 

 f£alanns crenatiis, Brug. 



„ tintinnabulum, Linn. 



