198 



HALF AN HOUB WITH SHELL-FISH. 



Fig. 104. 



Chiton marmoreum. 



been extracted from it. We have several species, 

 all of which more or less affect the same habits, 

 and are to be found under 

 stones at low water. The 

 largest is Chiton ruber, and 

 the commonest Chiton cine- 

 reus, an ashen, grey-coloured 

 shell, often mottled with 

 yellow or chocolate. The 

 " Key-hole Limpets " (Fissurella) take their name 

 from their peculiar appearance, which is as if the 

 Fi 105 common limpet had had its apex cut 

 off so as to leave an aperture resembling 

 a key-hole. This hole is used by the 

 animal for discharging the effete and 

 ia used-up sea-water. The " Notched Lim- 

 pets (EmwffinuJa, Fig. 105) have, 

 as their name implies, a small vertical notch cut 

 in the basal portion of the shell, Fig. 105. These 

 are, perhaps, the most elegant 

 of the limpets, the white, 

 finely-ribbed shell having the 

 apex gently curved over. The 

 gill-plumes are arranged on 

 each side the animal's body. 



Next we come to the " Top- 

 shells," most of which are 

 shore-loving species, and de- 

 servedly rank among the most 

 beautiful of our native mollusca. Trochus zizy- 



Fig. 106. 



Trochus zizyphinus. 



