The Wing Shells, Pearl Oysters and Hammer Oysters 



radiating lines. Young shells are adorned with minute, fimbriated 

 scales all over the surface. These disappear later. The pearly 

 lining is beautifully iridescent. Length, 5 to 8 inches. 



Habitat. — West Indies, Moluccas. 



The Atlantic Wing Shell (A. Atlantica, Lam.) is reddish 

 brown with numerous undulating wrinkles, separated into radiat- 

 ing series by white lines spreading from the umbones to the mar- 

 gins. The wrinkles are set with sharp spines, which are soon 

 worn off with the fibrous epidermis. Wing, a straight, narrow 

 blade. European forms, thin, pale, flat, long-winged and spiny, 

 are a contrast to our thick, dark-coloured, smooth ones, with 

 short wing and rounded, concave valves. Length, 3 to 4 inches. 



Habitat. — Mediterranean, northward. North Carohna to 

 Florida and West Indies. 



The Bearded Wing Shell (A. barbata, Rve.) is orbicular 

 in outline, with a straight hinge line, and no wing extension. 

 This yellow shell bears series of concentric laminae, which change 

 near the margin into a series of regularly overlapping, spoon- 

 shaped lobes, forming a heavy fringe. Diameter, 3 to 5 inches. 



Habitat. — Panama. 



The Emerald W^ing Shell {A. smaragdina, Rve.) an elon- 

 gated oval form, almost without a hint of a wing behind, is 

 smooth and a rich dark green in colour. Yet it swings off very 

 obliquely from the hinge, and is recognisable as an Avicula in 

 spite of its unusual form. 



The Great Pearl Oyster {A. margaritifera, Lam.) better 

 known to the commercial world by its sub-generic surname, 

 Meleagrina, is a wing shell with wings reduced to small angular 

 projections near the hinge of the large, flat circular valves. The 

 outside surface shows a coarse, laminated structure, of dull olive 

 to smoke colour. Within, the thick pearly lining is a beautiful, 

 iridescent expanse, interrupted by a central muscle scar. 



When small, the valves are ribbed and wear a luxuriant 

 growth of long, flat scales, twisted and curved like fronds of 

 coral. These disappear as the shell grows larger and thicker. 

 At maturity it is often ten to eighteen inches across and sur- 

 prisingly heavy. 



Pearl oysters live in tropical seas on clean, sandy bottoms 

 fifteen to twenty fathoms down. The strong byssal cord thrown 

 out through the hinge anchors the mollusk to coral masses or to 



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