jats:titleAbstract</jats:title> jats:pSome planes in sedimentary rocks contain features that appear to lie near equally spaced parallel lines. Determining whether or not they do so can provide information on possible mechanisms for their formation. The problem is recast here in terms of circular statistics, enabling closeness of candidate sets of lines to the points to be measured by a mean resultant length. This leads to a test of goodness of fit and to estimates of the direction of the lines and of the spacing between them. Two contrasting data sets are analysed.</jats:p>