The Williamia gussoni species is a gastropod mollusc from the Heterobranchia subclass and from the Siphonariidae family, also known as false limpets.
Until now, this species had been cited in the Mediterranean and the middle eastern Atlantic (Canary Islands, Madeira, African coasts), but always from the shell or from dead specimens in the middle of algae samples, especially of the genus Peyssonnelia.
Our collaborator and member of the directive board Xavier Salvador photographed the first live specimen in the field, on the night of September 30 at the Coves de Cala Maset, Sant Feliu de Guíxols. The observation was made on the alga Peyssonnelia coriacea.
This species can be confused with the limpet Tectura virginea, which has a similar pattern but does not have a protoconch, the tip points the head and present antennas, while Williamia does not present it and the tip faces back.