Beroes are ferocious predators upon their own kind, especially Pleurobrachia. They have thousands of tiny teeth (macrocilia) which puncture their prey--this is so that they can eat other ctenophores.
Some deep sea species are highly pigmented (ctenophores are usually transparent).
In order to swim better, Beroes keep their mouths closed to create a more streamlined body and reduce drag. In order to keep its mouth closed, the Beroe has two specialized strips of epithelial cells around its lips which act as a seal.