I owe a huge debt of gratitude to Dave Behrens and Terry Gosliner for their incredibly helpful assistance in identifying my nudibranch photos. For the vast majority of my photos, they turned my "I think it could possibly be..." into a positive i.d.

Australia

Chromodoris strigata Chromodoris strigata	Flabellina rubrolineata Flabellina rubrolineata	Platydoris formosa Platydoris formosa
Reticulidia fungia Reticulidia fungia

Like Nudibranchs, the following is an Opisthobranch:

Chelidonura inornata Chelidonura inornata

Channel Islands

MacFarland's Chromodorid Chromodoris macfarlandi	Cuthona lagunae Cuthona lagunae	Diaulula nobilis Diaulula nobilis
White Spotted Porostome Doriopsilla albopunctata	Spanish Shawl Flabellina iodinea	Opalescent Nudibranch Hermissenda crassicornis
Peltodoris mullineri Peltodoris mullineri	Hilton's Aeolid Phidiana hiltoni	Black Dorid Polycera atra

Like Nudibranchs, the following are Opisthobranchs:

Black Sea Hare Aplysia vaccaria

Navanax Navanax inermis

Costa Rica

Flabellina marcusorum Flabellina marcusorum

Indonesia

Aegires minor Aegires minor	Ardeadoris egretta Ardeadoris egretta	Chromodoris kuniei Chromodoris kuniei
Flabellina rubrolineata Flabellina rubrolineata	Glossodoris tibboeli Glossodoris tibboeli	Halgerda batangas Halgerda batangas
Hypselodoris iacula Hypselodoris iacula	Jorunna funebris Jorunna funebris	Nembrotha cristata Nembrotha cristata
Nembrotha purpureolineolata Nembrotha purpureolineolata	Phyllidiella pustulosa Phyllidiella pustulosa	Phyllodesmium kabiranum Phyllodesmium kabiranum
Tambja gabrielae Tambja gabrielae

Like Nudibranchs, the following is an Opisthobranch:

Chelidonura hirundinina Chelidonura hirundinina