OEOLOOT. 127 



Arne) of two species of edtbU estuary shells embedded in a stiff 

 mud, extending over an area not exceeding twenty three feet 

 by seven feet in diameter, and eighteen inches at its greatest 

 thickness, is not analogous to this, excepting the circumstance 

 of the occurrence of a portion of a bone. 



Having thus fur given an opinion against the theory that these 

 marine shells were introduced through the agency of the sea, it 

 becomes necessary that I should also state what I conceive to be 

 a more probable solution of the mystery. I would observe, that 

 the marine and the land shells are intimately associated in one 

 and the same matrix : both therefore, must have been deposited 

 by one and the same agent, whatever that agent may have been. 

 I believe that I am not speaking incautiously in asserting it to 

 have been the Blashenwell stream. Mr. Mansel referred to my 

 sxiggestion, stating it to be also the opinion of Mr. Bristowe, 

 that the marine shells might have been conveyed inland by sea- 

 birds to the open plains, whence they were washed down by the 

 surface water into the stream. I do not wish, however, to ad- 

 vance this opinion as a decided one ; for I apprehend diflSculties 

 in such a theory, which I cannot reconcile with natural results. 

 The shells in question are those of the limpet and the winkle : 

 the first is well known to adhere most tightly to rocks which are 

 covered by the sea at high water, and imless the knife is 

 cautiously inserted beneath the shell at a time when it is raised 

 by its inmate, who, immediately upon the approach of danger, 

 retightens it, its separation from the rock is not easily effected, 

 and, in fact, it can seldom be displaced without injury to the 

 shell. Nor do I think that any of our sea-fowl, with the exception 

 of the oyster catcher, which seldom flies inland, have the power 

 of separating the limpet from its native rock, without first break- 

 ing the shell. The winkle, a univalve abundant at low water, 

 especially upon the mud-lands of the north shores of the island, 

 may be obtained by birds, but even then the prize would be 

 beyond their reach. In this case, the bird must necessarily break 

 the shell, before it could devour the winkle contained within. 

 The thrush, for instance, betakes itself to a stone, and, with 

 the help of this breaks the shell of the snail upon which it feeds. 



