Berry's Bobtail Squid, Humming-bird Bobtail Squid

"Small bobtail squid, spherical body, 2 large rounded fins at the poterior end. Large eyes. A layer of iridescent cells gives to the animal a typical blue green, changing colour. When the chromatophores (the cells with the brown pygment) expand, the iridescence is concealed. Four rows of suckers on the tentacles. A light organ exist on the belly, that hosts bioluminescnt bacteria. Light emission is adjusted according the environmental light, and hides the silhouette of the squid, seen from below, against the bright background of the sea surface. Body 5 cm. Encountered on sandy bottoms, usually in lagoon or bay. Buried under the sand at day, it can glue sand on its back using glue glands. It swims at night, using the light organ for camouflage when approaching the preys (normally benthic crustaceans)."
Source: http://www.seadb.net/en_Bobtail-squid-Euprymna-berryi_501.htm