David Fleetham / Close up of the pattern on the Hawaiian spotted flatworm (Pseudobiceros) endemic to Hawaii.

Pascal Kobeh / Glorious flatworm (Pseudobiceros gloriosus) New Caledonia, Pacific Ocean.

David Hall / Polyclad flatworm (Pseudobiceros uniarborensis). Komodo, Indonesia.

Magnus Lundgren / Wild Wonders of China / Free swimming flatworm (Pseudobiceros hancockanus) Xiaoliuqiu Island, Taiwan

Georgette Douwma / Glorious flatworm (Pseudobiceros gloriosus). West Papua, Indonesia. Indo-West Pacific.

Georgette Douwma / Flatworm, probably Pseudobiceros sp, West Papua, Indonesia.

Constantinos Petrinos / Marine flatworm (Pseudobiceros flowersi) with ruffled marginal tentacles - pseudotentacles. Lembeh Strait, North Sulawesi, Indonesia.

Constantinos Petrinos / Marine flatworm (Pseudobiceros flowersi) with ruffled marginal tentacles - pseudotentacles. Lembeh Strait, North Sulawesi, Indonesia.e shown that fish will spit them out after the briefest of nips. We...

Georgette Douwma / Polyclad flatworm (Pseudobiceros fulgor). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Bedford's flatworm (Pseudobiceros bedfordi) on coral, Komodo NP, Indonesia, Indo-pacific.

Chris Newbert / Polyclad (Pseudobiceros sp) detail of skin, Papua New Guinea

David Fleetham / Hawaiian spotted flatworm (Pseudobiceros sp.), endemic to Hawaii, on a Large pincushion starfish (Culcita novaeguineae).

Fred Bavendam / Flatworm (Pseudobiceros bedfordi) crawling across coral, Great Barrier Reef, Australia

Georgette Douwma / Composite image of marine invertebrates on black background. Top row from left: Tube anemone (Ceriantharia), Yellow sea cucumber (Colochirus robustus), Nudibranch (Nembrotha lineolata), Squat shri...

Franco Banfi / Black flatworm (Pseudobiceros splendidus) on encrusting sponge, Ponza island, Italy, Tyrrhenian Sea, Mediterranean.

Franco Banfi / Black flatworm (Pseudobiceros splendidus) on encrusting sponge, Ponza island, Italy, Tyrrhenian Sea, Mediterranean.

Franco Banfi / Black flatworm (Pseudobiceros splendidus) on encrusting sponge, Ponza island, Italy, Tyrrhenian Sea, Mediterranean.

Linda Pitkin / Flatworm (Pseudobiceros kryptos), swimming at night. Lembeh Strait, North Sulawesi, Indonesia.