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          | To 
              about 1 cm across. Conical shell made up of plates. Commonly seen 
              on boulders on many of our shores usually crowded in lower portions 
          and shaded crevices. Also on living crabs and living snails.           | 
          0.5-1cm 
            across. Flatter shell forms star-like rays where it attaches to the 
            rock. Operculum conical and protrudes from the opening. Usually found 
            higher up on rocks and walls in small crowded clusters. | 
          To 
            about 3cm across. Tall conical shells not made up of plates, with 
            a ridged texture, small shell opening operculum recessed. On large 
            boulders.  | 
            | 
            | 
        
         
          |  
               
              Stalked barnacles 
              Lepas sp. 
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              Parasitic barnacles 
              Thompsonia sp. 
           | 
           
               
              Coral barnacles 
              Pygoma sp. 
           | 
            
            Sponge barnacles 
              Membranobalanus longirostrum
  | 
            | 
        
         
          | About 
            2cm. Usually attached to hard surfaces that float in the open sea, 
            and rarely found on the shore. Shells thin made up of several plates, 
            on a leathery stalk. Sometimes seen on large objects that have been 
            floating in the open sea. | 
          Barnacle 
            is invisible, but eventually produces tiny egg sacs that emerge through 
            the joints of the infected crab. Infected crabs sometimes seen on 
            our Northern shores. | 
          Tiny 
            slits (0.2cm) sometimes blue on the surface of hard corals. Sometimes 
            seen on our Southern shores. | 
          Tiny 
            feet (0.5cm long) with white spots, sticking o ut of holes in the Chocolate sponge.  Sometimes 
            seen on some of our  shores. | 
            |