Nuttall, history of discoveries on Acystosporidae, [103]

Nutting, [276], [280] n.

Nyctotherus, [137];

habitat of, [152]

Obelia, [280]

Oceanapia, [223]

Ocellus, [252]

Octactine, [200]

Octactinellida, [208]

Octotremacis, [346]