Colonial tunicates are rarely that regular, Chuck. I'd go for cheilostome bryozoan. The more conspicuous bryozoans are erect, branching structures but some are flat, encrusting rocks, algae, shells, etc. Take a look at this: http://www.science-in-salamanca.tas.csi ... sipora.htm
Thanks Leslie. I tend to not think of bryzoans as they seem to be a rare find and rarely kept alive. But now that you mention it I can see what you mean. I need to find some myself for reference.
