20 



CHAPTER IV. 



HOME or THE PHOLA.S. — CHARACTERS. — SHELL. — SUPPLEMENTARY CON- 

 TRIVANCES. — LIGHT FROM DARKNESS. — BRITISH KINDS. — CUP-BEARING 

 PHOLAS. — GROWTH AND HABITS. 



PHOLAS. 



On tlie low rocks of our coasts near low-water mark may 

 be founds snugly ensconced in close-fitting lioles^ leaving 

 very small openings at the surface^ specimens of a long- 

 sliaped mollusc with a pair of colourless shells. You can- 

 not get at them without breaking open the chalky red sand- 

 stone, lias, or decayed wood in which they are ioibedded ; 

 and, when first intruded upon, they are very apt to spurt 

 out a jet of water from the fleshy tube. The Pholas lies 

 head downwards in the cell, which fits his body, and into 

 which he made his way when very young. The two valves 

 of the shell are generally oval or cylindrical, and the front 

 or lower part of them is covered by sharp points, arranged 



