Monterey Bay Aquarium Research Institute cc
The Pacific Barreleye fish - Macropinna microstoma - is the only species of fish in the genus Macropinna, belonging to Opisthoproctidae, the barreleye family. It is recognized for a highly unusual transparent, fluid-filled dome on its head, through which the lenses of its eyes can be seen. The eyes have a barrel shape and can be rotated to point either forward or straight up, looking through the fish's transparent dome.
(thanks Miss Rare)