Péist Mhilteogach
Foirmíonn an phéist ghuaireach sceireacha bithghineacha. Déanann gach péist bheag feadán gainmheach dó féin a ghreamaíonn le feadán nó carraig eile, agus dá réir a chruthaíonn sceir atá cosúil le cíor mheala. Nuair atá an taoide istigh, bogann cinn na mbraiteog amach chun bia atá ag imeacht thar bráid a ghaistiú. Is fíor-annamh a fheictear a leithéid.
Honeycombe Worm
This bristle worm forms biogenic reefs. Each little worm makes for itself a sandy tube, which it sticks to another tube or a rock, thus creating the honeycomb-like reef. When the tide is in, tentacle heads poke out to trap passing food. It is quite rare.