Study area description: Rocky intertidal zone (max depth 1.5m) in Alykes (Crete, Eastern Mediterranean), Elounda (Crete, Eastern Mediterranean), Evripos channel (Euboea, Eastern Mediterranean), Thermaikos Gulf (Eastern Mediterranean, Nea Roda (North Aegean Sea, Eastern Mediterranean), Porto Karas (North Aegean Sea, Eastern Mediterranean), Zingaro (Sicily, Italy), Capo Gallo (Sicily, Italy), Balestrate (Italy) Sampling protocol: Some samples were collected by scraping off the surface of a 20x20 cm square, stored in plastic bags, sieved through 0.4 mm mesh size in the lab and preserved in a 4% solution of formalin and sea water. Other samples were taken according to the sampling protocol described in "Iken, K., Konar, B. 2003. Natural Geography in Nearshore Areas (NaGISA): the nearshore component of the Census of Marine Life. Gayana 67: 53-160." And other samples were taken according to the sampling protocol described in "Kitsos M.S., 2003. Contribution to the study of the biodiversity of the midlittoral and supralittoral hard substratum assemblages. Aristotle University of Thessaloniki, Phd thesis, 1-299pp." Preparation method: For some samples, the whole animal was fixed and preserved in 96% ethanol. For other samples, the whole animal was fixed in formalin and sea water 4%. Quality control: Standardization against the World Register of Marine species and recent taxonomic reviews. Subjective synonyms are kept in the dataset with their original name and a reference to the currently accepted name. The dataset is published under a Creative Commons CCZero license