64 Shell Life 



affects (7 to 90 fathoms), a band of epidermis will 

 usually be found bordering the lower margin. Large 

 examples measure 21 inches across. It would appear 

 that many fishes not strong enough to crush this 

 solid shell yet make attempts to wrest its valves 

 apart, for great preparations have been made to 

 keep off such enemies. The valves are united by a 

 number of bundles of ligament, attached to long 

 triangular cavities sunk in the shell between the 

 beak and the broad hinge-plate. The hinge-teeth 

 are thick, and in adults number about six on each 

 end of this plate, which is plain in the centre, though 

 young individuals exhibit a few minute teeth here. 

 The impressions of the mantle and muscles are very 

 deep on the interior, and the flat, lower margin is 

 impressed with about 50 teeth, in appearance like 

 the edge of a coarse comb. Those of the two valves 

 interlock, and so prevent the slightest shifting by the 

 most powerful assailant w^hen the shell is closed. 

 In spite of this, it has one enemy that it cannot defy. 

 This is the Cat-fish, which cracks the stony shells with 

 its long powerful teeth as though they were nuts. 

 The animal is of sluggish habit, and lives on the 

 surface of gravel and among "nullipore," all round 

 our coasts. It does not burrow, and therefore has 

 no siphons, but the edge of the mantle is somewhat 

 contracted and protruded at the hinder side of the 

 shell ; at this part, too, it is studded with a great 

 number of black eye-spots. 



The Eared Limopsis (Limoj^sis auriUt) somewhat 

 resembles the Dog - Cockle internally, thougli the 

 shell is less round and owes its name to a fancied 

 likeness to Lima, the File-shell. Altliongh common 



