The distribution of redshifts within individual redshift-magnitude bands contains a significant periodic structure of ‘X-groups’ which cross the bands at a steep angle. Six independent cluster samples indicate that the pattern appears to be fixed in redshift and magnitude. Five compact E-dominated groups of galaxies are superposed and shown to concentrate at the boundaries between X-groups. Morphology is shown to be ordered across X-groups, suggesting evolutionary sequences linking groups. All correlations are demonstrated with several independent data samples.