Spines are generally coloured, with pigment incorporated into the calcite of the skeleton. In cross-section (SEM micrographs below) spines may be hollow or solid. The hollow core to a spine is called ...

This is smooth and shiny because it has a solid calcite veneer. It may either be perforate (as in ... and a camarodont (non-crenulate and imperforate); the latter is an SEM micrograph.