Top dollar

Recently I experimented with taking extreme close-ups of a Pacific Sand Dollar (Dendraster excentricus).  The spines on the top (aboral) surface are club-shaped, which creates very interesting patterns:

 

 

Beautiful, aren't they?

P.S.  I've written about sand dollars on the NHBH a few times, but the first post called "Petals and grooves" is a good introduction if you'd like to learn more about these fascinating relatives of sea urchins.