CHAPTER XXXII: THE SCALLOPS. COMB 

 SHELLS 



Family Pectinid/E 



Shell bivalve, free or attached, orbicular, ribbed, unequal, 

 with ear-like extensions of the hinge line; internal ligament in 

 pit under beak; foot small, finger-like, with large byssal glahd; 

 mantle open, with double border of fringed tentacles, and row 

 of conspicuous eyes; siphons none. 



Genus PECTEN, O. F. Miill. 



Characters of the family. Distribution world-wide. Two 

 hundred species. Multitudes assembling on a restricted area, 

 form "scallop banks" from which are dredged several species 

 used as food. The adductor muscle is eaten. Found in shallow 

 water to two hundred fathoms depth. 



The scallop's shell is admirably adapted to protect without 

 overburdening its occupant. The valves are arched and plaited 

 to give the greatest strength with the minimum of weight. The 

 wide hinge is the fulcrum upon which the central adductor muscle 

 acts to shut the two valves at will, and the resilient ligament 

 opens them. 



The shell rests upon the right valve, which is arched and 

 smooth and pale compared with its mate. The anterior ear is 

 the more prominent one. There is a close interlocking of the 

 margins when the muscle contracts, except for a misfit of the large 

 ear. A notch permits the passage of the byssus, the cord by 

 which the mollusk attaches itself. A glutinous secretion of the 

 byssal gland is extruded from pores, and these threads are man- 

 ipulated by the finger-like foot to form a rope before they become 

 toughened by their contact with sea water. 



Young scallops are all able to spin this byssus at will. They 

 tether themselves by it to objects on the sea bottom, and cast 



411 



