236 



POPULAR CONCHOLOGY. 



Saxicava. Fleuriau de Bellevue. (Hiatella Daudin ; 

 Diotonta Schum ; Byssoyma Cu- 

 vier; Pholeobius Leach ; Rhom- 

 boides Blain. ; Biapholius Leach.} 0h 

 — Shell transverse, inequilateral, 

 thick, gaping, rather variable in ^0 

 form ; ligament external ; teeth 



° t < Saxicava rugosa. 



nearly obsolete or indistinct. 



Animal oblong, or claviform ; mantle closed in front, except 

 a very small opening for the passage of a digitiform foot, 

 which is furnished with a byssal groove ; siphons united 

 nearly to the extremities ; branchial and anal orifices large, 

 margined with a fringe of (simple) cirrhi.* — Several 

 species ; also fossil. 



The Saxicava perforate, or inhabit holes in rocks, oyster- 

 shells, and roots of seaweeds. They are found in the South 

 Sea, Mediterranean, Northern Ocean, &c. They live in 

 calcareous rocks, into which the animal penetrates by 

 means of its rasp-like foot, fretting it away very slowly, 

 but yet sufficiently fast for the increasing size of its 

 own body and shell, and thus forming a secure retreat. 

 Masses of rock on the coast of England are frequently 

 found pierced with innumerable small holes, the entrances 

 to the habitations of these animals. In some places 

 they actually do an immense amount of mischief; for 

 in a few years they will destroy walls built of stone to 

 prevent the incursions of the sea, perforating them till 

 they are perfectly honeycombed, or fretted away. This 

 has been the case with sea walls at Devonport, built of 

 Portland stone. It has been observed that the operations 

 of these little soft-bodied creatures have in some places 

 " destroyed rocks, and made deep water where shoals 



* Forbes's British Moll. 



