These are small squid (about 4-6 cm mantle length from what I can tell) that can live below 1000 meters. They have really cool "tails" but I am not yet sure if this is a larval feature that goes away with maturation. They are known to maintain larval tentacle clubs into adulthood.
P. danae - photo from mbari.org
More info here
P. danae - photo from mbari.org
More info here