O. flabellum, transverse section, [69]

Olfactory organs, [155], [390] f., [391], [392]

Olfactory pit, [129]

Oligopleuridae, [545], [544]

Oligopleurus, [545]

Oligorus, [659]

Oligosarcus, [575]

Oligotrema, [78], [111] n.

Olt, [584] n.

Olyra, [588]