We don't know a whole lot about their anatomy and physiology, but we do know that they lack "typical" octopus features, like ink sacs and the ability to move around by jet propulsion. Instead, cirrates swim using those fins on the sides of their heads. As for the eponymous "cirra", those are little filaments, similar to the cilia that line your nose, which are paired up with every sucker on a Cirrate octopus' arm. Nobody knows exactly what they do, but they may be involved, somehow, in trapping and handling of food.
http://www.boingboing.net/2010/10/21/weird...able-cirra.html