178 O. W. Lamplugh — The Shell-bed at Sjpeeton. 



The following species have been obtained : ^ 



Ttiiina Balthica. 

 Psammobia sp. (fide Phillips). 

 Mactra sp. ( ,, ,, ). 



Scrobicularia piperata. 

 Cardium edule. 



Mytilus edulis. 

 Liitorina littorea. 



,, rud'S, var. 

 Hydrobia ulvte. 

 Utriculus obtusus, var. prefenuis. 



As noticed by Prof. Phillips, the bivalves generally occur vi^ith 

 valves united ; but they are not often in the attitude of life ; usually 

 having the umbos upwards, and with the valves gaping open. 

 Single shells do occur, and also an occasional imperfect valve ; but, 

 on the whole, they show very few signs of wave action, and appear 

 to have been left by quietly receding tide- waters on a muddy flat. 

 Another proof of the quietness of the waters is the sharply-fractured 

 and unabraded state of the broken Belemnites, which, with a few 

 other pebbles, are sparsely scattered through the lower part of the 

 sands. 



That the bed accumulated slowly is shown by the difference iu 

 fauna and lithological character between the upper and lower parts 

 of the deposit ; the result of some slight and gradual change in the 

 surrounding conditions, probably a slight deepening of the water 

 with an accelerated current. 



The shells confirm the idea strongly suggested by the shape 

 of the ground that the beds were formed at the mouth of a quiet 

 tidal estuary. When the waters of the sea stood at the level 

 indicated, the glacial and later beds which now cumber the Vale 

 being then unformed, what is now the Vale of Pickering would 

 then be a wide, shallow, land-locked estuary receiving the copious 

 drainage of the Eastern Moorlands, which now flows through the 

 narrow gorge at Castle Howard to join the Ouse. The piece of 

 light jet found in the deposit tells of distant erosion in the Upper 

 Lias, having doubtless been brought down by the old river from 

 the higher reaches of the valley, north of Pickering, 



Unfortunately the above limited shell-list yields us little evidence 

 as to the age of the bed. Tellina Balthica, however, shows that it 

 cannot be so old as the Eed Crag ; and as it will be shown to underlie 

 the oldest Yorkshire Glacial deposit, its age must lie somewhere 

 between then and early Glacial times. 



Its Extent and StratigrapMcal Relations. — By far the clearest and 

 best exposure of these shelly sands is the one described above, on 

 the dividing ridge between " Middle " and " New Closes Cliif," about 

 half a mile north of Speeton Gap (where the Chalk ends). On 

 the south side of this ridge they end abrupt!}', having been carried 

 away by a huge slip, and portions of them may sometimes be seen 

 down at the level of high-tide ; but beyond this, though I have 

 carefully sought over the slipped ground up to the foot of the 

 chalk scarp, I have not been able to find any traces of them. Tlie 

 accompanying chalk-gravel, rapidly increasing in thickness and in 

 roughness as we approach its parent-slope, can be followed through- 



* I have to thank Dr. Gwyn Jeffreys for his kindness in examining these shells 

 for me. 



