> [!summary]- Classification
**Kingdom**:: Vegetals
**unranked**:: Viridiplantae
**Division**:: Chlorophyta
**Class**:: Ulvophyceae
**Subclass**::
**Order**:: Bryopsidales
**Suborder**::
**Superfamily**::
**Family**:: Halimedaceae
**Subfamily**::
**Genus**:: Halimeda
**Species**:: H. tuna
**Vernacular**:: Sea cactus
## Photos
*[106 - 2022-12-01 - Naama Bay Beach - Sharm Al Sheikh - Egypt](106%20-%202022-12-01%20-%20Naama%20Bay%20Beach%20-%20Sharm%20Al%20Sheikh%20-%20Egypt.md) - By night.*
*[109 - 2023-02-26 - Coucoune - Saint Pierre - Martinique](109%20-%202023-02-26%20-%20Coucoune%20-%20Saint%20Pierre%20-%20Martinique.md) - With [Neophinon marianus - Longjaw squirrelfish](Neophinon%20marianus%20-%20Longjaw%20squirrelfish.md), a little [Niphates digitalis - Pink vase sponge](Niphates%20digitalis%20-%20Pink%20vase%20sponge.md) and a [Agelas conifera - Brown tube sponge](Agelas%20conifera%20-%20Brown%20tube%20sponge.md) in the background.*
## Notes
Common name in French is "Monnaie de Poséidon" (Poseidon's coin), abundant in Mediterranean Sea.
## References
- https://en.wikipedia.org/wiki/Halimeda_tuna
- https://doris.ffessm.fr/Especes/Halimeda-tuna-Monnaie-de-Poseidon-1395/(rOffset)/0