MYTILIDJB. 
375 
Greenlcmdicum, Chemnitz (Fig. 161) ; others, and by far the greater 
number, are furnished with regular sides, generally obtuse, sometimes 
ln ridges diverging from the point and armed with straight or curved 
s pines, arranged in the oddest manner, as in Cardium aculeatum 
(Fig. 162). 
In C. Mans (Fig. 160), the mantle has a large opening in front, 
fringed anteriorly with papillae in the form of tentacula; the in- 
habitant of the shell has a very large foot, with a bend or knee near 
the middle ; its mouth is transverse and funnel-shaped, and furnished 
with a triangular appendage. One of the peculiarities in the organ- 
ization of these molluscs is its direct connection with their mode of life. 
In short, these molluscs, which most commonly live on the sea shore, 
a nd bury themselves in the sand to the depth of four or five inches, 
are enabled to breathe, to draw water for then- nourishment, and also 
Fig. 162. Cardium aculeatum (Limneus). Fig. 163. Cardiurn edulus (Linnsens). 
to throw off the products of digestion, by having the mantle prolonged 
mto two tubes, the orifices of which reach to the surface of the soil. 
% means of these feet and an extremely curious organ of locomotion, 
tile Cardiums can at will issue from their holes and re-enter them. 
■I lie fishermen of the shore easily recognise the presence of these 
a nimals by the little jets of water which they throw up through the 
sands. 
These molluscs are found in every sea on the globe, and under all 
latitudes. Many of them belong to our own and the French coasts, 
where they are eagerly sought for by collectors, as well as for food. 
Hie flesh of the animal, however, is coriaceous, aud little esteemed. 
File species most common on the littoral of the Atlantic is Cardium 
e dulus (Fig. 163), its white or fawn-coloured shell being hollowed out 
