The duplicatus variety is when a layered cloud occurs at two altitudes at the same time. In the high-level Cirrus and Cirrostratus clouds, you can most readily identify the split layers of duplicatus when they happen to have the filaments of the fibratus species. The fibres of each layer can point different ways with differing wind directions at each altitude. Since these clouds are made of ice crystals and so are generally semi-transparent, the layers appear as one, with the beautiful cross-hatched pattern shown here.