Spine......

..........Covered
 
 Shell of the kina - also known as sea urchin or sea egg.
 
This shows many of the long and short movable spines and tube feet which cover the shell when the kina is alive.  
Usually, when they are found washed up on the beaches they no longer have these spines.  
 
 
Thank you  for the comments, stars and hearts for yesterday’s blip featuring the redundant pump for MonoModay’s ‘grunge’ theme.