Right whales or black whales are three species of large baleen whales of the genus "Eubalaena": the North Atlantic right whale ("E. glacialis"), the North Pacific right whale ("E. japonica") and the Southern right whale ("E. australis"). They are classified in the family Balaenidae with the bowhead whale. Right whales have rotund bodies with arching rostrums, V-shaped blowholes and dark gray or black skin. The most distinguishing feature of a right whale is the rough patches of skin on its head, which appear white due to parasitism by whale lice. Right whales can grow up to more than long with a highest-recorded length of . Right whales are very robust whales, weighing or more. The largest known right whales can attain in length and weigh up to . Specimens measuring and weighing are documented in whaling records but not scientifically confirmed. Their immense bulk makes right whales significantly heavier than other whales of similar or greater length such as the humpback, gray, sperm and even fin whales. In fact, right whales rank only behind the blue whale in sheer body mass. One (apocryphal) explanation for their name is that whalers identified them as the "right" whale to kill on a hunt due to the plentiful oil and baleen they could provide.