MOLLUSKS 135 
and is fastened to the rock or other body upon which the jingle 
shell is growing. This stalk of attachment is in reality the byssus, 
and when first formed it is flexible as are the attaching threads of 
many other clams and mussels. 
The jingle shell is found from the West Indies to Cape Cod, 
and is very abundant in Long Island Sound. It is, however, rare 
north of Massachusetts Bay, 
although it has been found as 
far north as Cape Sable. Itisa 
shallow water form, not living 
at a depth greater than 70 feet. 
The dead shells are of 
considerable commercial im- 
portance, for they are used by 
the oystermen to be strewn 
over the beds in order to give 
the little oyster a good surface 
upon which to set. The shell 
is well figured in Verrill and Fig. 97; JINGLE SHELL UPON A ROCK. 
Smith’s “Invertebrates of Long Island Sound. 
Vineyard Sound,” p. 17 (311), 
Plate XXII, Figs. 241, 242, under the name of Anomia glabra. 
The Pearl Oyster, ( Meleagrina margaritifera). This species and 
several closely related varieties furnish the most valuable mother of 
pearl and precious pearls known. The pearl oysters are especially 
abundant in the Indian Ocean and tropical Pacific but they are also 

found in the Gulf of California, the Red Sea, and sparingly in the 
West Indies. The fisheries of the Persian Gulf are worth $2,000,000 
annually and those of Ceylon are almost as valuable. About 15,- 
OOO tons of pearl shells are used by the world each year, the value 
of which ranges from about S900 to S250 per ton. The pearl 
oyster is a large, flat bivalve, with-a long, straight hinge, and quite 
regularly curved contour to the shell, and is about ten inches broad. 
On the outside the shell is dark-olive often mottled with irregularly 
crescent-shaped yellowish spots, or streaked with broken yellowish 
lines radiating from the apex. The outer skin of the shell is rough 
and flakes off into long, ragged, scale-like projections, especially near 
the outer edges. Inside one finds the beautiful nacre of the shell 
