It does not form (or at least not always) a shelly support, but corrodes the surface of the shell to which it is attached, so as to form a more flat attachment, and to leave a lunate convex rib instead of the lunate muscular impression which is observed on those specimens or individuals which have a shelly base.
96.

Siphonaria radiata, Var.

Gray, Phil.Mag.1824.

275.
Siphonaria exigua, Sow.

Gen.
Patella japonica, Donovan.
Icon.