Page:Popular Science Monthly Volume 50.djvu/61

Rh water is warm. The shells range in color from pure white, through all shades of yellow, to bright orange, and some are exquisitely banded and shaded with light and dark brown. The edge of the mantle is fringed with long and short tentacles, among which are thirty silver-blue eyes. As they are not as highly organized as our eyes, Pecten needs a much larger number of them. The scallops, unlike most of the mollusks, can swim through the water



by rapidly opening and shutting the valves. Closing them suddenly drives out the water in a powerful jet, which by reaction sends the shell forward. It must be a strange and beautiful sight to see a flock of these "butterflies" flying through the blue water on a fair summer day. Scallops used to be known in Europe as pilgrim shells, because they were used by the pilgrims of the middle ages as a badge.

A most remarkable family of shellfish are the piddocks, living in England, America, and Borneo. They are all borers. The shells of those which inhabit the English chalk cliffs are snow-white, to match their home. Some bore in rock, some in the red chalk, and the most wonderful of all, the East Indian species, lives in the trunks of dead trees. Their shells are covered with deep grooves crossing each other and forming a sort of rasp. The foot, which is covered with a hard dermal armor, is pressed against the sides and the shell turned about, thus easily scooping out a cavity in the soft chalk. The piddock continually floods his burrow with water to wash out the particles of chalk that collect as he works. The piddock has a little light of its own, so that it could travel safely about after dark were it necessary. This is a peculiarity of many of the creatures of the sea, and often on a summer night in the tropics the water is ablaze with their phosphorescence.

Mussels, living in both salt and fresh water, form a large class of mollusks. Some of them can climb about on the rocks by throwing out a byssus thread, pulling themselves up, then fastening another above that, and so on.

The horse mussel is one of the largest, and very interesting on account of a boarder which it often entertains. A tiny crustacean, the pea crab, lives inside its shell in peace and happiness. The crab is not a parasite, as it does not live on the mussel itself, but merely a messmate eating the refuse of its food.