Two major biogenic formations, composed mainly by dead corallites of the Mediterranean stony coral (Cladocora caespitosa), have been recently studied in Slovenian marine waters. The paper presents new data about the presence of coralline algae on the biogenic formation situated off Cape Ronek and off Cape Debeli rti\u10d. Coralline algae are very important for the creation, development and maintenance of calcareous bio-concretions that offer new niches for many invertebrates and other algae. They are listed as important builders of the coralligenous biocoenosis in the \u201cDraft Lists of coralligenous/ma\uebrl populations and of main species to be considered by the inventory and monitoring\u201d of the RAC-SPA, and should be further deeply studied and appropriately protected
