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Piddocks

Some pholads burrow into oyster shells, some in hard timber, one in floating cakes of wax on the Cuban coast; an Australian species is found in resin; a fossil species resembles Teredo in lining its burrow with shell. A fresh water species works in wood several miles above the mouth of a Bornean river.

Genus XYLOPHAGA, Turt.

Shell globular, with cross furrows; gapes in front; is closed behind; burrow oval, with shelly lining; animal withdraws within shell, except siphons; foot thick, extensible.

The Wood Piddock (X. dorsalis, Turt.) of Europe and America, is a little nut-like mollusk, boring wood to the depth of an inch, and apparently eating the sawdust it makes. It always works across the grain. The boring instrument is the long elastic foot. The shell is covered with epidermis. Length, 1 inch.

This wood borer is in a sense a connecting link between Pholas and Teredo, at least as far as choice of material for burrowing goes.

Habitat.-North Atlantic Ocean.