Obba listeri 
Occelated Blue-ringed Octopus 
Oceanic Squid 
Ocellate Phyllidia 
Octopus laqueus 
Odontoglaja guamensis 
Okenia brunneomaculata 
Okenia nakamotoensis 
Oliva keenii 
Oospira penangensis 
Opalescent inshore squid 
Opalescent Sea Slug 
Opisthoporus biciliatus 
Orange-banded Arion 
Oregon forestsnail 
Ornate Sap-sucking Slug 
Ovatipsa chinensis 
Oxynoe viridis 
Pacific banana slug 
Pacific plate limpet 
Pacific sideband 
Painted Elysia 
Painted Snail 
Palio gaeli