PINNA SEA WING. 187 



sinks generally a depth of twenty or thirty yards ; 

 then quickly proceeding to his work, he tears the 

 muscles from their bed, fills his net, makes a 

 signal and is drawn up again to the surface. 

 Many and great are the dangers attendant on 

 this employment. The greedy shark marks the 

 diver for his prey, who seeks to elude his obser- 

 vation by muddying the water. A large flat fish 

 also sometimes attacks him, and keeps him un- 

 der water till he is drowned. When drawn up in 

 safety to his vessels, he often in consequence of 

 his exertion discharges blood from his mouth and 

 nostrils. The divers rest and labour alternately, 

 during periods of about ten minutes. 



GENUS. PINNA* 



SEA WING. 



Generic character. Shell bivalve, equivalve, 

 fragile, thin, gaping at one end, and furnished 

 with a byssus ; shape subtriangular, narrow at 

 the beaks, and expanding to a considerable 

 breadth at the opposite extremity ; hinge with- 

 out teeth ; valves united by a long external 

 ligament. 



* Plate X. figure 3. 



