Fish scale the surface, interacting only with the riblet tips, not causing any high-veloctiy flow in the valleys. Since this high velocity flow now only interacts with the riblet-tip, which is a very small surface area, the momentum transfer which causes drag is now much lower than before, thereby effectively reducing drag. Also, this reduces the cross-stream velocity fluctuations, which aids in momentum transfer too. The rough, sandpaper-like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was
Creatures the World Forgot of the first and third of the series. "Creatures the World Forgot" is not related to two later, similarly titled films, "The Land That Time Forgot" (1975), and "The People That Time Forgot" (1977). These were made by Amicus Productions and both starred Doug McClure. Creatures the World Forgot Creatures the World Forgot is a 1971 adventure film directed by Don Chaffey and produced and written for Hammer Films by Michael Carreras. The film concentrates on the daily struggle to survive of a tribe of Stone Age men. Very little dialogue is spoken throughout the film, apart from a few