Calcarea

The Mediterranean Sea hosts 2 Sub-classes, 4 Orders, 14 Families, 24 Genera and 79 Species of calcareous sponges. Each species is exhaustively described and illustrated by means of historical and unpublished images of the skeleton and of sponge anatomy, in light and scanning electron microscopy. Distribution patterns are reported, as well as keys for the identification of different taxa. The present account is not a taxonomic revision of the group but, in some cases, some decisions and suggestions are proposed