Photo: W. A. Green. 



THE BORING PURPLE SEA-URCHIN, STRONGYLOCENTROLUS LIVIDUS, IN A ROCK POOL, BUNDORAN 

 These Urchins bore cavities for themselves in the Carboniferous Limestone, and are sometimes permanently sealed up in their holes 

 by the growth of a calcareous seaweed that covers the rocks. In some cases one side of the cav.ty ,s wholly composed of the calcareous 

 Alga The method by which the hole is bored is uncertain, but it is probably chemical. The subject requ.res re-mvest.gat.on. 



