What is 'furrow whale'

DID YOU KNOW? 

• The narwhal's tusk is in fact a canine tooth that can grow up to 3m in length. It is thought to be a symbol of sexual power within males, rather like a lion's mane, helping to establish rank within hierarchies.
• Sperm whales can reach depths of around 3km beneath the ocean's surface, staying submerged for up to two hours. What are they doing down there? One of their favourite foods is giant squid, which lives in the depths of the ocean. Occasionally sperm whales are seen with scars obtained from their deep sea battles.
• There's a species of toothed whale called the Perrin's beaked whale, and rather remarkably, no-one has ever knowingly seen a live one. In the 1970s, a few dead individuals were discovered on the Californian coastline, and were identified as other species. Later DNA testing of them revealed that they were in fact a completely new species to science, and they were given the name Perrin's beaked whale. No-one has positively identified one since.
• All toothed whales, including dolphins and porpoises, have a melon. This sounds rather an odd statement, until you realise that 'melon' is the term given to a fatty organ in their forehead which is thought to be used to aid echolocation. In some species, such as the beluga, the melon can cause a pronounced cranial bulge.
• Belugas, the all-white toothed whales of the Arctic, are often known as sea canaries because of their high-pitched twitter.
• The large whales known as rorquals all have pronounced grooves that run from their mouths and along the underside of their bodies. These grooves, which are actually folds of skin, enable the mouth to widen in huge gapes when feeding. The word 'rorqual' itself actually comes from the Norwegian for 'furrow whale'

from : http://uk.whales.org/