36 



Shell Life 



changed habits in the creature that makes it, may 

 be seen clearly in the case of the Blue-rayed Limpet 

 {Helcion). In its young condition it should 

 be souofht on the broad fronds of the large 

 tangles and oar - weed. 

 The form of the thin 

 shell well suits it for this 

 situation, the frond float- 



Pelican's-foot 



shell offering little opposition 

 to the flow of the water. As 



the frond waves iridescent gleams play upon its 

 purple-brown, and in order that the Blue-rayed 

 Limpet may not be readily seen it bears upon its 

 clear brown shell from, tliree to six fine lines of 

 bright blue radiating from the apex and giving 

 an effect similar to that seen on the tangles. As 

 it gets older this Limpet climbs down the stalk, 

 where there is no iridescence, and finally is to be 

 found among the root-like suckers by which the 

 weed is attached to the rock. In such a situation 

 there is more risk to the shell from the rush of 

 stones, etc., at tlie lower level. The shell, in con- 

 sequence, becomes much tliickened, the edges are 

 modified to fit it for adhering to the cylindrical 

 stem instead of the plane surface of the frond, and 

 as the blue lines would be an attraction rather than 

 a disguise they are gradually obscured. The shell 



