A bizarre deep-water fish called the Barreleye has a transparent head and tubular eyes.  Since the fish’s discovery in 1939, biologists have known the eyes were very good at collecting light.  But their shape seemed to leave the fish with tunnel vision.  Now scientists say the eyes rotate, allowing the Barreleye to see directly forward or look upward through its transparent head.  The Barreleye (Macropinna microstoma) is adapted for life in a pitch-black environment of the deep sea, where sunlight does not reach. They use their ultra-sensitive tubular eyes to search for the faint silhouettes of prey overhead.

(Source: theoceaniswonderful)