CHAPTER IV: THE PIDDOCKS 



Family PholadidyE 



Shell bivalve, gaping at both ends; valves thin, white, hard, 

 brittle, with rasp-Uke, overlapping laminations in front; hinge 

 plate reflected over the umbones and a long curved, spoon-like 

 process under each, for the attachment of muscles; accessory 

 valves often present, external to the original shell; pallial sinus 

 deep. Animal club-shaped; foot truncated in front; mantle 

 closed, except pedal orifice; siphons large, long, united except 

 near ciliated ends; branchial siphon (containing gills) closed 

 throughout; hinge ligament strong, elastic, external. 



A familyof several genera of moUusks, living and fossil, which 

 perforate rocks, clay or wood with vertical burrows, symmetrical 

 and rarely in contact. 



Genus PHOLAS, Linn. 



Shell gaping, cylindrical; dorsal margin protected by two 

 accessory valves, one anterior, one posterior; beaks covered; 

 combined siphons form a large cylindrical tube, ciliated at end. 

 Foot short, large. The property of shining in the dark is common 

 to the whole genus. 



These burrowing shell-fish have a brief infancy of freedom, 

 then settle down for life in a cell dug by themselves in rock or 

 clay, or wood. Granite is not too hard for some species. The 

 burrow is made by constantly turning the shell about in its close 

 quarters, so that the hard rasp-like surface grinds off the inner 

 wall, the foot clasping the support by suction. At first, the en- 

 .trance is made by rubbing the rock surface with sand particles 

 grasped by the foot. There is no moving out for the piddock. 

 ,He is safe and comfortable; food and oxygen are within reach 

 of his long siphons ; his chief enemies are starfish and crustaceans 

 which tear or nip off the ends of his siphons before they can be 

 withdrawn. 



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