favellidium
[ fav-uh-lid-ee-uh m ]
/ ˌfæv əˈlɪd i əm /
noun, plural fav·el·lid·i·a [fav-uh-lid-ee-uh] /ˌfæv əˈlɪd i ə/.
(in certain red algae) a cystocarp wholly or partly immersed in a frond.