203 Mr. R. Walker on Clays, containing Fossils, 



P. pellucida, Littorina littoralis, L. littorea, and many broken 

 fragments of other littoral shells. The third bed, although 

 distinct enough, seems to be merely a mixture of the materials 

 of the second and fourth beds ; the only shells observed were a 

 few straggling specimens of Littorina. In composition, the 

 fourth bed has a greater resemblance to estuary silt than to any 

 other kind of deposit : it shows no traces of lamination, and, 

 with the exception of occasional thin layers of sand, it bears no 

 other marks of stratification. From this bed the mammalian 

 bones and the following shells were obtained ; the latter seemed 

 to be distributed through the mass, as far as it was pierced. Of 

 the bivalve shells, the most common was Tellina proxima, of 

 which specimens of all sizes were in abundance ; and, as usual 

 with this species, the valves were covered with a yellow epider- 

 mis, which in most cases, however, adhered more firmly to the clay 

 than to the shell. There were likewise a considerable number 

 of specimens of Scrohicularia piperata, Mytilus edulis, Cardium 

 edule, and two or three examples of Saxicava rugosa. Of the 

 univalves, Rissoa ulva was in the greatest abundance — in some 

 places completely crowded, more especially where there was a 

 lamina of sand. Littorina littorea was plentiful ; there were two 

 specimens of Nassa incrassata, and two or three oi Helix hispida. 

 The univalves were all full-grown specimens ; but none of the 

 bivalves, with the exception of Scrohicularia and Tellina, had 

 attained full dimensions. They were all very friable, and in the 

 case of Mytilus and Cardium it was scarcely possible, in many 

 instances, to remove them from the clay without breaking. In 

 every instance both valves were adherent ; and there can be no 

 doubt whatever that the animals lived and died where their shells 

 were afterwards found. All the marine shells of the preceding 

 list are living in the littoral zone of the adjacent sea, with the 

 exception of l^ellina proxima, which does not appear to be living 

 now in any part of the British seas, and is considered a charac- 

 teristic shell of the glacial deposits of Scotland ; they are all 

 included in Geikie^s Catalogue of Organic Remains from the 

 Glacial Deposits of Scotland*; they are likewise included in 

 Wood^s ' Mollusca of the Crag / so that as species they must 

 have existed during many of the physical changes that have oc- 

 curred on the earth toward the latter epochs of its history. 



Of vegetable remains noticed, there were pieces of the branches 

 of the birch and the oak, together with a few nuts of the latter. 

 Of the birch- branches, however, there was little else than the 

 bark preserved, which did not appear to be at all wasted. There 

 were also a few fragmentary impressions of leaves, and many 

 impressions and remains of what appeared to have been marsh- 

 * The Glacial Drift of Scotland. 



