HALIOTIS. CYCLOBRANCHIATA j LIMPETS; CHITONS. 387 



spiral. In the Haliotis, the shell is slightly twisted ; and from 

 a faint resemblance it is thought to bear to the ear of a quadruped, 

 it has been called the Sea Ear. This animal, in its living state, 

 is one of the most beautiful of Gasteropods, on account of the 

 variety and richness of its colours. Its shell, when the surface is 

 polished, possesses a pearly lustre, with resplendent metallic 

 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 adhering 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 place the hand or some instru- 

 ment under its edge (which is usually a little separated from the 

 rock when the animal is undisturbed) ; and to endeavour to 

 remove it before the animal is alarmed. When this attempt 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 occurred 

 to men, who have incautiously attempted to remove these shells, 

 when under water. 



ORDER VIII. CYCLOBRANCHIATA. 



928. The general form of the Limpets, which principally 

 compose this Order, 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 

 the formation of the shell, are the Chitons ; of which some small 

 species inhabit our shores, but which attain to much greater size 

 between the tropics. Their shell (Fig. 584) is composed of a num- 

 ber of plates arranged behind one another with great regularity, and 

 connected by a very complex series of ligaments and muscles, 

 which reminds the Naturalist of those which unite and move the 

 different segments in the Articulated animals. The Limpets 

 and Chitons fix themselves to the rock, in the same manner as 

 the Haliotis ; and it is stated that Crows and other birds, 



