The common limpet is a specially interesting and abundant example of the more primitive Aspidobranchia.
Thus, then, we find that the limpet possesses a symmetrically disposed pair of ctenidia in a rudimentary condition, and justifies its position among Aspidobranchia.
It is probable that the limpet takes several years to attain full growth, and during that period it frequents the same spot, which becomes gradually sunk below the surrounding surface, especially if the rock be carbonate of lime.
The eyes of the limpet deserve mention as examples of the most primitive kind of eye in the Molluscan series.
Ab, g, The limpet breeds upon the southern English coast in the early part of April, but its development has not been followed.
At low tide the limpet (being a strictly intertidal organism) is exposed to the air, and (according to trustworthy observers) quits its attachment and walks away in search of food (minute encrusting algae), and then once more returns to the identical spot, not an inch in diameter, which belongs, as it were, to it.
The foot of the limpet is a nearly circular disk of muscular tissue; in front, projecting from and raised above it, are the head and neck (figs.