114 



WEST COAST SHELLS 



divided into two parts by a narrow constriction. 

 The shell is whitish in color like that of all the pid- 

 docks, and it is only about half an inch long. 



Figure 89 gives a 

 good idea of the shell 

 of the Rough Pid- 

 dock, Zirplicza cris- 

 pata^ Linn. This fine 

 borer is able to force 

 a tunnel into the 



Fig. 89 



hardest of blue clay, 

 doubtless by means of its sharp rasp. There is no 

 accessory plate over the hinge-area in this species, 

 but it is protected by a membrane, and in front of 

 the umbones the valves are refiexed. The shell is 

 thin, white, and very hard, and its length is from 

 two to four inches. This species is widely dis- 

 tributed, being found in both great oceans. 



It is said that all of the piddocks give out a phos- 

 phorescent light when they are alive, and that this 

 light may be seen by carefully removing specimens 

 from their homes in the rocks and placing them in 

 a pan of sea water. Great care is necessary to pre- 

 vent the creatures from receiving injury, as the 

 shells are very delicate. Some of my younger 

 readers may have an opportunity to experiment in 

 this line and watch in the darkness for signs of light 

 from the living animals. It is possible, also, that 

 some one may even detect them in the act of boring 

 their holes. The sea is very large, and there are op- 

 portunities for a bright boy or girl to observe much 

 that is really valuable. 



