Genus Plakina Schulze, 1880

Definition. ENcRUSTINg PLAkINIdAE USUALLy WITH dIOdS, TRIOdS, cALTHROPS (ALL MAy bE AbSENT), ANd ALWAyS WITH AT LEAST

ONE TyPE Of HOMOLOPHOSE cALTHROPS, WHIcH MAy HAVE ONE TO fOUR LOPHATE AcTINES ANd dIffERENT RAMIfIcATION PATTERNS. IRREgULAR SPIcULES ARE cOMMON ANd INTRASPEcIfIc VARIATION IN SPIcULE SHAPE MAy bE HIgH. ONE SPEcIES HAS PAPILLAE ANd A MIcROcAVITy-fILLINg HAbIT, ANd IN ANOTHER SPEcIES THE SkELETON IS AbSENT (LAgE et al. 2018).

Type species. Plakina monolopha ScHULZE, 1880 .

Measurements are min–med–max full spicule size in micrometres. Number of measurements in parenthesis. *, colour after fixation in ethanol.