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FIRST BOOK OF ZOOLOGY. 



the barnacles. They are found in immense nmnbers cover- 

 ing the rocks and piers' in places between high and low 

 water mark. In nearly all places along the coast the rocks 

 are whitened by their numbers. Pupils living inland can 

 get specimens of the barnacle by visiting places where oys- 

 ters are received in the shell ; and, by examining the shells 

 as they are thrown away, may now and then come across 

 good specimens. With a stiff brush and some water the 

 mud may be washed off the shell; and then the creature will 

 present the following appearance. 



Fig. 139. — Barnacle on Otster-Siiell. — The circular scar on the shell indicates the place 

 from which another barnacle had been taken. 



The barnacle-shell is roiiiid and conical, broad at the 

 base by which it is firmly attached to the rock or whatever 

 object it grows upon. The walls of this shell are composed 

 of six pieces whose edges overlap each other. The opening 

 in the top of the shell is closed by four plates which tightly 

 fit together. 



In collecting these creatures for the purpose of studying 

 them alive, care must be taken in breaking them from the 



