BIVALVES. 
31 
are very small and convex ; the lunule is indis¬ 
tinct, and the hinge-line is without teeth. 
The Swan Mussels live in lakes, ponds, canals, 
and muddy rivers, and are found in suitable 
localities throughout the kingdom. 
Anodons vary very much, not only according 
to locality, but in the same waters; some of the 
numerous varieties should, it is thought, be more 
justly regarded as species. In ponds where 
there is plenty of food, and where the water is 
nearly stagnant, they become of large size, with 
ventricose thin shells, and are type forms ; whilst 
in more rapid rivers, with pure clear water, with 
very little decomposing animal or vegetable 
matter, they are small and comparatively longer 
than A. cygneus , with compressed thick shells, 
and are the A. anatinus (Pl. II., fig. 4) of some 
authors; but all intermediate forms and sizes 
may be observed. 
The manner of locomotion is slow and regular, 
leaving their tracks distinctly discernible in the 
soft mud. At Bottesford, on the Trent, where 
at high tides the water is salt, it is found in 
great abundance. 
Anodons are thrown up in quantities on the 
shores of Lough Schur, co. Leitrim, where they 
are eaten by the peasantry. Sliggaun is the 
common name applied to the Swan Mussel in the 
North of Ireland. 
