HALIOTIS ; FISSURELLID.K J CALYPTR^ID^. CYCLOBRANCHIATA. 383 



the variety and richness of its colours. Its shell, when the sur- 

 face is polished, possesses a pearly lustre, with resplendent me- 

 tallic hues. It is consequently much sought for as an ornament. 

 The animal attaches itself to the rock, after the manner of a 

 Limpet, by a large muscular foot ; and the extent of the adher- 

 ing surface is so great, that a very considerable force is required 

 to detach it, when the animal is putting forth its strength. The 

 best mode of obtaining the shell, is to plftce the hand or some 

 instrument under its edge (which is usually a little separated 

 from the rock when the animal is undisturbed), and to endea- 

 vour to remove it before the animal is alarmed. When this at- 

 tempt is not successful, the animal draws its shell down upon the 

 rock with such firmness, as to grasp most securely anything that 

 is under its edge ; and in this manner fatal accidents have oc- 

 curred to men, who have incautiously attempted to remove these 

 shells, when under water. The Haliotis is very abundant on 

 the shores of the Channel Islands, where it is cooked and eaten. 

 The other species referred to this family have the shell of a more 

 distinctly spiral form. The nearly allied FISSURELLIDJE have a 

 conical shell, like that of the common Limpet, but furnished with 

 a small aperture at the apex for the escape of the branchial cur- 

 rent ; hence they have received the name of Key-hole Limpets. 

 In the CALYPTR^ID^E, or Bonnet-limpets, also, the shell has 

 nearly the same form, but the apex is somewhat spiral, and the 

 interior is usually provided with a shelly plate, which is some- 

 times arranged spirally. They adhere firmly to rocks and 

 shells, where they appear to pass a perfectly sedentary existence ; 

 the shells being usually fitted to any irregularities of the surface, 

 whilst in some cases the rock is more or less hollowed out by 

 the foot of the animal. 



SECTION B. CYCLOBRANCHIATA. 



1000. The general form of the Limpets, which principally 

 compose this Section, is well known ; and the peculiarity in the 

 position of their gills has already been mentioned. Closely allied 

 to the Limpets in general structure, but differing remarkably in 



