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
|

Coryphellina sp. 1
Coryphellina sp. 1 |

Platydoris formosa
Platydoris formosa |

Reticulidia fungia
Reticulidia fungia
|
Like Nudibranchs, the following is an Opisthobranch:

Mariaglaja inornata
Mariaglaja inornata
|
Channel Islands

Diaulula
nobilis
Diaulula
nobilis |

White
Spotted Porostome
Doriopsilla
albopunctata |

Felimida macfarlandi
Felimida macfarlandi |

Spanish Shawl
Flabellinopsis iodinea |

Opalescent
Nudibranch
Hermissenda opalescens |

Peltodoris mullineri
Peltodoris
mullineri |

Hilton's Aeolid
Phidiana hiltoni |

Black
Dorid
Polycera atra |

Tenellia lagunae
Tenellia lagunae |
Like Nudibranchs, the following are Opisthobranchs:

Black Sea Hare
Aplysia vaccaria
|

Navanax
Navanax inermis
|
Costa Rica

Coryphellina marcusorum
Coryphellina marcusorum |
Indonesia

Ardeadoris egretta
Ardeadoris egretta |

Coryphellina lotos
Coryphellina lotos |

Doriprismatica sp.
Doriprismatica sp. |

Goniobranchus kuniei
Goniobranchus kuniei |

Halgerda batangas
Halgerda batangas |

Hypselodoris iacula
Hypselodoris iacula |

Jorunna funebris
Jorunna funebris |

Nembrotha chamberlaini
Nembrotha chamberlaini |

Nembrotha cristata
Nembrotha cristata |

Notodoris minor
Notodoris minor |

Phyllidiella pustulosa
Phyllidiella pustulosa |

Phyllodesmium kabiranum
Phyllodesmium kabiranum |

Tambja gabrielae
Tambja gabrielae |
|
|
Like Nudibranchs, the following is an Opisthobranch:

Chelidonura hirundinina
Chelidonura hirundinina
|
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