Craca

Thank you so much for the info.

Yes... It's the comun name in portuguese.

Welcome Cláudio Marques, Is barnacle called Craca in Portugal?

It's done... Thank you friend. : )

Hi Cláudio Marques, It is a barnacle colony. So I guess you could change it to the arthropod category. I am not very sure of the species but I think it is Chthamalus stellatus [ from http://en.wikipedia.org/wiki/Barnacle the second photo on the right].