Opalescent sea slug
- kingdom: Animalia
- phylum: Mollusca
- class: Gastropoda
- order: Nudibranchia
- family: Facelinidae
- genus: Hermissenda
- species: Hermissenda crassicornis
Acapulco
Guerrero
Mexico
Koh Tao
Surat Thani
Thailand
Crescent City- La Jolla
- Monterey
- Morro Bay
- Pacific Grove
California- Gig Harbor
Washington
United States