tremoctopus violaceus

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Violet blanket octopus (Tremoctopus violaceus) is an example of extreme sexual dimorphism in a species: females can be up to 2m in length whereas males are a tiny 1-2cm creatures.
Jewelled Umbrella squid (Histioteuthis bonnellii).The jewels of this squid are bioluminescent photophores that cover its body and provide the most beautiful play of colours in deep see. 

From: Mollusques méditeranéens by Jean Baptiste Vérany (1851)