STONEBORING SHELL-FISH. 23 



and spray, and a loud roar. The surface of the rock 

 Itself, from some distance above high-water mark 

 downward, is corroded into a thousand little cavities, 

 all honey-combed, as it were, in the most irregular 

 manner, a circumstance which greatly facilitates the 

 action of the sea in wearing down the masses. These 

 cavities have been produced by a stoneboring shelled 

 Mollusk, Saxicava riujosa, which, as I believe, attacks 

 only limestone, but this, hard as it is, it burrows 

 through and through. It caji live only where it is 

 covered during a part of every tide ; and therefore as 

 part of this honey-combed structure is now above the 

 reach of the tide, it must be inferi'ed that this lime- 

 stone has been elevated, since the existence of these 

 stoneborers. It would be worth w^hile to inquire 

 how far the honey-combed limestones of other regions, 

 of the South side of Jamaica for example, may have 

 had a similar origin, though this is explained by 

 Sir H. de la Beche in a very different manner. 



One can scramble out upon the side of these rocks 

 at low water, and find between tide-marks a sort of 

 ledge sufficiently level to permit examination; though 

 the rough surface, and especially the sharp points 

 that project between the honey-combed cavities, ren- 

 der the footing precarious and uncomfortable. The 

 surface is leprous with myriads of acorn-shells, each 

 tenanted by its living inhabitant, and every one put- 

 ting forth, as soon as covered by the tide, its delicate 

 little grasping hand of feathery fingers, or, if you 

 please, its casting net, with which it is perpetually 

 making its little throws for passing prey. Limpets, 

 periwinkles, and murices also stud the rock, and in 



