CYCLOBKANCHIAL GASTEROPODS. 
439 
by watching the slow upheaval of the shell above the plane ot its 
position. It is supposed, from the mouth being armed on its upper 
edge with a large semi-lunar, homy, cutting tooth, and in its lower 
Part from having a tongue furnished with horny hooks, and from 
their inhabiting in great numbers places covered with marine plants, 
fhat their food is chiefly vegetable. 
300. Patella oerulea (Lamarck). Fig. 301. Patella umbella (Gmc-1.). 
The poorer inhabitants of the coast eat Limpets when they have 
Nothing else, but their flesh is singularly coriaceous and indigestible. 
They are found in every sea ; but are, however, found to be 
h^ger as well as more numerous, and much richer in colour, in 
Equatorial seas, and especially in the southern hemisphere, than in 
European seas. 
The common Limpet is thick, solid, oval, and nearly circular, 
generally conical, and covered with a great number of very fine stripes. 
Its colour is of a greenish grey, uniform above, and of a greenish 
yellow inside. It is abundant in the Channel and on Atlantic coasts. 
The Blue Limpet, Patella cserulea (Fig. 300), from St. Helena, 
E'ig. 302. Patella grauatlna (JJnnjeus). 
Fig. 303. Patella barbata (Lamarck). 
