The Pteria hirundo is a species of bivalve belonging to the family Pteriidae. The species is found in Europe, Africa and the Americas. The two valves are unequal and the lower one, to which the animal is anchored, is larger and hollow than the upper one. The mollusk has a rounded body, with the margins of the two edges of the mantle fringed.

Spondylus gaederopus is a species of marine bivalve mollusc, a thorny oyster in the family Spondylidae. This species is endemic to the Mediterranean Sea. Spondylus gaederopus attaches itself to the substrate with its lower valve, which is usually white, while the upper valve is usually purple. Specimens that are all white, or all purple do, however, exist.

Neopycnodonte cochlear is a species of marine bivalve molluscs belonging to the family Gryphaeidae.This species can be found in the North Atlantic Ocean (Azores) and in the Mediterranean Sea. The peculiarity we want to point out is that it is a small oyster that plays the same role as corals. That is, it forms aggregations as they grow and multiply, create agglomerations of more or less large dimensions comparable to corals.