Limpets. 105 
flat and concave form of the two valves of this 
shell, and also the depth of the indentations or 
ridges. 
LIMPETS. 
Among the rocks of the British coast there are 
no shells more frequently met with than those of 
the Common Limpet (Patella vulgata); they lie 
scattered about like so many little empty cups, each 
having, on the death of the molluks, fallen from the 
rocky cavity in which it was embedded, and which 
was just large enough to contain it. Here the 
animal attaches itself so firmly by its fibrous foot, 
which is hollow in the centre, and acts like a sucker, 
that it is almost impossible to loosen its hold other- 
wise than by inserting something thin, like the 
blade of a knife, between it and the stone. By this 
power of adhesion, the Limpet is protected from the 
violence of the waves, and also from its numerous 
enemies, aquatic birds and animals, which have a 
relish for its flesh. Still vast numbers are used as 
food, both by man and the inferior creatures, so 
that the means of defence furnished to the Limpets 
