The perils of <i>Cc</i> revisited

The space groups of 98 structures originally reported in Cc are revised. In 75 cases the revised space group is C 2/ c and the revision entails adding a center of symmetry, usually leading to large changes in bond lengths and angles. In the remaining 23 cases, where the revised space group is Fdd 2, R 3 c or (in one case) I \overline 4 c 2, the lattice type is changed but no center is added; in these cases the molecular dimensions are effectively unchanged.