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
Lampshades made from human skin After her conviction for war crimes, General Lucius D. Clay, the interim military governor of the American Zone in Germany, reduced her sentence to four years' prison on the grounds "there was no convincing evidence that she had selected Nazi concentration camp inmates for extermination in order to secure tattooed skins, or that she possessed any articles made of human skin". Jean Edward Smith in his biography, "Lucius D. Clay, an American Life", reported that the general had maintained that the leather lamp shades were really made out of goat skin. The book quotes a statement made by General Clay