Whales of the genus Balænoptera are so termed, being distinguished from the right whales by the possession of a small triangular adipose dorsal fin. There are several species, some of which grow to a greater length than any other animals of the order, viz. 80 or perhaps 90 feet. They are very active and difficult to harpoon, yield comparatively little oil, and their baleen, or "whalebone," is almost worthless; consequently, they suffer much less than the right whales from the persecutions of the whalers. The finner, or great black fish, is feared by whalers in general. It is vicious, and can only be attacked by large boats in shallow water, as at the Bermudas, where the whale-boats are about 50 or 60 feet long, and 12 feet beam. The fish yields one barrel of oil for every foot in length beyond thirty. (See razor-back and rorqual.)