This high, very thin layer of small, uniform, tiny cloudlets was observed in Boulder, Colorado on March 23, 2011. In this image ripples were visible at the upstream edge of the cloud formation, looking west. Since each of the cloudlets is less than a degree wide and unshaded, the cloud formation fits the World Meteorological Organization definition of cirrocumulus. However, there is some evidence that the cloud is altocumulus rather than cirrocumulus. For a discussion, see UCAR Magazine's Currents article at http://www2.ucar.edu/currents/cloud-remember-and-mystery-solve.
