286 



L WER IN VEU 1 'EBllA 7 'ES. 



they do not form tubes, nor do they, except JCijlup}iu(/u, live in wood. In Pholas tlie 

 valves are large and the shells are never completely closed in front. The shell is long 

 and cylindrical, and the pallia! sinus reaches to the middle of the valves. The com- 



_ mon name for these 



^ molluscs in England 

 ^ lb ])iddock, but no n]i- 

 _ jjellitive has gained 

 lE much currency here. 

 The species bore in 

 V uid, clay, limestone, 

 md even gnei.ss. 

 Doubtless here the 

 msti ument of boi-ing 

 I the foot with its 

 iidened de r m a 1 

 lunor. AVIien we 

 ( (insider tile liarduess 

 i)t some of the rocks 

 i( iforated, we crm 

 St iicely realize' llinl 

 this organ is suffi- 

 cient to produce the 

 effects, but time is a 

 matter of small im- 



r iLi -113 — I'ttoitiff jii JL"* miii'jw. 



portance to the pho- 

 As they increase in size they increase the size of the burrows, which are always 



lads. 



just a little larger than the shell. These burrows are always nearly vertical, and but 

 rarely encroach upon each othex'. 



In Europe the piddock are esteemed a delicacy, and on the coast of Normandy 

 their capture furnishes emj)loyment to a good many women and children, who jaill 

 them from their burrows with an iron hook. They are usually cooked, but are said U> 

 be very palatable raw. One remarkable peculiarity of the pholads is their phosphores- 

 cence or capacity of shining in the dark, which is here better developed than anywhere 

 else among the Mollusca, unless it be in PJiillirhoe. The common European s]iecies is 

 Fholas dactyhis, while on our coasts are found P. cost<(ta and P. tniiinifn. A closely 

 allied genus, Zirjj/uea, has a species, Z. crix- 

 pata, common both to New and Old England 

 and the northern waters between. In this 

 genus the shell is sliort and the accessdry 

 valves are absent. 



In another section of the family we find 

 pholads in which the anterior gape of the 

 shell is closed by a callous ])late. Here be- 

 long the genera Pholadidea and Martesia. 

 Martesia smithir, on our coast, burrows in oyster sliells, while other forms have differ- 

 ent h.abitats. While most of the Pholadidae are marine, Adams reports finding a 

 species in the fresh water of Borneo, living in dead trunks of trees. 



Fig, 31C.— y^njil,,^ 



