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      The Class Calcarea (Calcarean Sponges) differs from other classes by the mineralisation of the spicules, which are not formed by opal but by calcium carbonate (calcite, rarely by aragonite or by magnesium-rich calcite). The spicules are monoaxial, triradial or tetraradial.

Autor: Radek Vodrážka

In the Virtual Museum there are total 8 samples