540 O. W. Laniplugh — The Bridlington Shell-hed, etc. 



perfect state of preservation ; wliilst those wliich were broken were 

 probably broken either during the life of the animal or very 

 shortly after, as in one or two cases the umbos of fragmentary 

 bivalves remained together, though much of the shell was missing ; 

 showing, I think, that the ligament existed at the time; and some 

 fragments of Astarte and Ci/prina from Dimlington showed the 

 epidermis. 



From these patches I obtained twenty-eight species of mollusca 

 (for list see Appendix D), which Dr. J. Gwyn Jeffreys has had 

 the kindness to examine for me, and he has named four species 

 which are not included in the published lists of the Bridlington 

 shells, viz. Rissoa Wyville-Thomsoni, Menestho albula, Leda tenuis, 

 and Leda lenticula. 



I have picked out twelve species and varieties of Foraminifera 

 (see Appendix C), though doubtless a more experienced microscopist 

 would be able to detect many more. I have to thank Mr. H. B. 

 Brady for naming these for me. 



I have seen several other patches of this kind in the Basement 

 Boulder-clay, at various times, in exposures on the beach, to the 

 southward of this section,^ and nearer the place where the shells 

 were first found, but have not before seen them in section. 



It will be seen from the above-quoted descriptions of that bed, 

 that these shelly patches are essentially the same as the so-called 

 "Bridlington Crag," which was not really a hed at all in the 

 stricter sense of the word, but a similar, though more extensive 

 set of streaks and masses of sand and clay in Boulder-clay. 



Shells in Boulder-clay. — The surrounding Boulder-clay also 

 contains many shell-fragments, with now and then a perfect valve, 

 which have undoubtedly been derived from similar beds, having 

 been thoroughly kneaded up and mixed with glacial debris. This 

 is shown by the extremely patchy nature of the clay, even where 

 the shell-beds have been wholly destroyed, as on the south beach 

 at Bridlington, the clay varying in character from step to step. 



Then, too, under many of the unbroken valves, there still remains 

 a little coarse sand, showing the original matrix of the shells ; and 

 many of its boulders show PJiolas and Clioncs borings; and these 

 borings contain in many instances the same coarse green sand. As 

 not one, but several kinds of rock are bored, the bottom on which 

 the shells lived would seem to have been strewn with boulders. 



As a curious illustration of glacial erosion, I may mention the 

 finding in this Boulder-clay, on the south beach, of a Tellina baUhica 

 with valves united and perfectly unbroken. Sand filled the interior, 

 but all around was Boulder-clay, — the shell, in fact, occurred as an 

 erratic pebble ; — which, I think, shows well how misleading may be 

 the evidence of a few selected specimens as to the general conditions 

 of the bed from which they came; certainly no one would have 

 judged this shell to be from the Boulder-clay. 



Of twenty-five species identified from the "Basement" Clay at 

 Bridlington (Appendix E), only one species and one variety are 



1 Geol. Mag. Dec. II. Vol. VI. p. 399. 



