Opesia, [524]

Ophelia, [299], [332];

eggs, [275];

coelomic corpuscles, [252]

Opheliidae, [258], [331];

gill, [265];

ciliated pits, [272]

Ophiodromus, [308];

O. flexuosus, parasitic, [297]

Ophryotrocha, [310], [320];