on respiratory function of Aristotle's lantern, [527];
on pedicellariae of Sphaerechinus, [541]
Uintacrinus, [588]
Ulmaridae, [324]
Umbellula, [331], [359], [360], [363];
U. gracilis, [359]
Umbellulidae, [362]
Umbrella of Medusae, [251]
on respiratory function of Aristotle's lantern, [527];
on pedicellariae of Sphaerechinus, [541]
Uintacrinus, [588]
Ulmaridae, [324]
Umbellula, [331], [359], [360], [363];
U. gracilis, [359]
Umbellulidae, [362]
Umbrella of Medusae, [251]