Notidanidae, [442], [279];

persistent nephrostomes, [401]

Notidanus, [443], [345];

spiral valve, [267];

N. cinereus, branchial clefts, [277];

skull, [222];

N. griseus, branchial clefts, [277]

Notochord, [3];

of Enteropneusta, [14];

of Cephalodiscus, [24], [25];