Qapers^ Piddocks^ and SJiip-zvorms 163 



Flask-sliell 



callow the foot to protrude. The siphons are long, 

 semi-transparent, united, and capable of extension to 

 several times the length of the animal. It 

 bores into limestone, old shells, and red sand- 

 stone, but always fashions for itself, when 

 full-grown, a flask-shaped jacket composed of 

 shell-fragments and sand cemented together. 

 It occurs only on the south coast of England, 

 the Welsh coast, and the south and west of 

 Ireland, from low water to 20 fathoms. At 

 Torbay its burrows in the new red sandstone 

 are beautifully finished off as though lined 

 with porcelain. 



The Piddocks form the sub-order Phola- 

 dacea. They are all borers into rock or wood, and 

 they exhibit a remarkable advance in shell develop- 

 ment, the typical species being pro- 

 vided with supplementary valves in 

 addition to the two that normally 

 enclose the animal. The white shell 

 gapes at each end, and though thin 

 and brittle, is exceedingly hard, the 

 front part often armed with toothed 

 ridges that form a good rasp. There 

 are no hinge-teeth and no ligament, the valves 

 being held together by the adductor muscles 

 only. The hinge-plate is continued outside, and 

 folds over the upper margin of the shell, where 

 it is protected by a portion of the mantle. To 

 protect the mantle, one or more accessory valves 

 cover it at this part. The front pair of adductor 

 muscles are attached to the hinge-plates, where their 

 impressions will be found. The mantle impression 



Case of Flask-shell 



