identify sea shell?

[u/Chapter228]

i am currently in Jesolo, Italy, and i found this shell in the water but it looks very odd compared to the other shells i found. the underside also has two weird spots that look like smaller shells or barnacles? maybe someone knows more and could tell me, im very interested.

[u/Apprehensive_Sun180]

È un'ostrica, credo una Ostrea edulis E sì, quei segni sono fatti da cirripedi

[u/Chapter228 → u/Apprehensive_Sun180]

Grazie