1 66 



Shell Life 



not of the same character as the two large valves 



that enclose the animal, so that it will be better to 

 speak of them as dorsal shields. In 

 this species there are four of these 

 dorsal shields; two in front and side by 

 side, a third more solid, behind and inter- 

 locking with these, whilst the fourth is 

 long and slender, and protects the mantle 

 and upper margins of the valves. The 

 animal is whitish like its shell. The 

 siphons are covered with little fleshy 

 points, the sheath brown or speckled. 

 Although chiefly found in the English 

 and Bristol Channels, it is recorded from 

 Seacombe, Lancashire, and along the 

 south, east, and north 

 coasts of Ireland. It 

 is not particular in 



its choice of material in which 



to bore, chalk, slate - rock, red 



sandstone, submerged w^ood, and 



even peat, being selected in dif- 

 ferent localities. 



The White Piddock (P. can- 



dida) is a smaller species (less 



than 3 inches long), and has a 



thinner, more convex shell than 



the foregoing, the prickles form 



from 25 to 30 rows only, the 



front gapes less. The reflected 



hinge-plate forms but a single fold 



externally, which is not partitioned off" into cells : 



and there is but one dorsal, lance-shaped shield with 



Dorsal shields 



Common Piddock in 

 its cell 



