CORALLINE CRAG. 
41 
mixture of derivative fossils. Two or three drifted land shells 
are the sole evidence of the proximity of land. 
The nature of the deposits and the character of the fauna both 
point to the Coralline Crag as having originated as a sandbank far 
from shore in a warm, moderately shallow sea. It is very difficult 
to match it exactly at the present day ; none of our English 
dredgings correspond very closely. Mediterranean dredgings are 
often more similar, though I have been unable to find any records 
of a Bryozoan deposit such as this. The conditions seem more 
like those we find among the Azores or off the coast of Portugal, 
where the current of the Gulf Stream and the Atlantic waves 
must keep the clear warm water in constant movement to a con¬ 
siderable depth, and so encourage the growth of Bryozoa. Off 
Portugal, however, the water deepens rapidly, and there is no 
wide submarine plateau, such as seems to have existed during 
the Older Pliocene period in our latitudes, owing to the sub¬ 
mergence of a considerable part of the continental area. 
