Many distributions of sedimentologic (and other geologic) data are non-Gaussian. Of nine examples studied in detail, seven are Pearson's Type IV, and two are Pearson's Type I. Each plots as a zig-zag line composed of two or more straight-line segments on probability paper. The zig-zag pattern appears to be caused by a deficiency of particles of certain sizes. This is perhaps a general, rather than a local, condition, as has been pointed out by many workers.