From our description of two-dimensional maps of spiral galaxies we conclude that the simple picture of spirals being axially symmetric disks in circular motion needs a revision of first order. We have distinguished five types of deviations from circular motion, each of them presenting a dynamical problem in its own right. Obviously most of these problems have been recognized before in the literature. We have discussed them here from an overall point of view as a first and necessary step to relate the dynamics of spiral galaxies to their morphological properties.