The File Shells Family Limidae

THE FILE SHELLS FAMILY LIMIDAE. Genus LIMA, Brug.

Shell

obliquely oval, eared, white, gaping at the sides; hinge toothless, with triangular ligament pit; umbones well apart; surface sculptured with radiating ridges bearing numerous imbricated, spiny points ; mantle inflated, bag-like, open, fringed at border, set with eyes; foot finger-like; gills 4, equal on each side, distinct. A large family, mostly extinct.

The roughened surfaces of all these white shells suggest that they might serve as rasping tools. The scoop shape is constant. The depth of the shells is variable. Chiefly inhabitants of the Red Sea and Mediterranean, yet a few species are scattered in the East and West Indies, Australia and Northern Europe.

In more ways than a few the file shells resemble the scal lops. But they outdo them at many points. A school of young sters with shells like carved ivory, flit through the water, zigzag ging with all the suddenness and swiftness of the scallops, but they go hinge foremost, and trail after them a graceful and copious sheaf of long mantle tentacles. They often throw these about each other, and thus adhering, swim by twos and threes. Drawn in, these fringes are rigid horns guarding the gaping valves. Dr. Jeffreys had a Lima in his aquarium which clasped his finger with its tentacles. He drew it about for awhile, then attempted to shake it off, but failed. He had to tear several filaments from the mantle ; and even then, they continued to writhe and cling as if alive and determined to hold on. They were removed with considerable difficulty.

When free life palls, the Lima can attach itself by a byssus. This is detachable at will. Many prefer to remain stationary, so they build about their shells a web of byssal threads, plastered with slime in which fragments of shells, seaweeds, coral, and 408 The File Shells pebbles have place. Strangely enough, two or three young ones may be found in one nest, but adults are alone, in such close quar ters that they cannot turn around without the greatest effort. But they are able to move up and down, as the nest is funnel shaped. They retire when prowling crabs and hungry fish ap proach.

The Oriental File Shell (L. orientalis, Ads. and Rve.) is found with its interesting nest attached to stones well off our west coast. Mrs. Oldroyd described one she took from the dredge at San Pedro, and put into a jar of sea water. It came out of the nest and swam gracefully about, occasionally putting the foot out as if to help it along. The white shell, obliquely oval,

and set with rows of fine, file teeth, had rose pink mantle fringes, short but numerous, which merged into white for one-third of the border. This species is L. dehiscens, Conr. Length, l to 3 inches.

Habitat.— Monterey southward, California.

The Gaping File Shell (L. hians, Gmel.) has strong, rough ribs, and in all particulars seems able to take care of itself. The body is red, and the mantle orange, trailing a thousand long filaments, that curl and twist constantly, like the tentacles of a sea anemone. In the nest of this species the little porcelain crab lives, with full consent of the owner. It probably acts as scavenger, keeping the house clean in exchange for its lodging. Length, 2 inches.

Habitat.— British Isles.

The Fragile File Shell (L. Loscombii, Sby.) small, finely ribbed, and delicate, with bright orange body and tentacles, lives on muddy bottoms from shallow water to one hundred fathoms depth. Cod and other fish are very fond of this little bivalve. To escape the enemy it bores holes in clay bottom to hide in. Nests cunningly covered with bits of shells and other debris are built where the bottom is too hard to burrow into. Length, I inch.

Habitat.— British Isles.

The Excavated File Shell (L. excavata, Chemn.) is the largest species now living. Its oval valves are thin and shallow, the surface faintly cross-striated. The posterior ears are well developed ; the anterior ones are drawn in, forming part of an excavated area that is sharply angled on the thickened margin 409 The File Shells of the left valve. Through the opening made by this marginal angle, the byssus passes out. Length, 4 to 5 inches.

Habitat.— Norway.

The Rough File Shell (L. scabra, Dillw.) has its ridged surface set with small pointed scales, and covered with a yellow ish epidermis.. The shell is comparatively thick and ovate, with the large, anterior ears reflected. Length, 2 to 4 inches. ' Habitat.— Southern Florida, West Indies.

The Frilled File Shell (L. squamosa, Lam. ) has its rounded ridges decorated with erect, flat, scaly plates. The general outline of each valve is obliquely ovate. The ears are and depressed, the hinge oblique. Length, t to 3 'inches.

Habitat.— Red Sea, Mediterranean, West Indies, Philippines.

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