160 THE ELEMENTS 



Pentagonal, having five angles. 



Perforated, pierced with holes. 



Pervious, admitting passage. 



Phosphorescent, emitting light in the 

 dark. 



Pillar, the columella, or perpendicular 

 centre which extends from the base 

 to the apex, in most of the spiral 

 shells. 



Plaits, folds. 



Plicated, folded or plaited, as in the 

 pillar of the volute tribe. 



Prismatic, generally applied to the 

 colours of shells, bein^ like those 

 of the prism. 



Porcate, marked with raised longi- 

 tudinal lines. 



Protrude, to thrust forward. 



Protuberances, plaits higher or more 

 elevated than the parts adjoining. 



Punctated, with small dots or punc- 

 tures like a thimble. 



