Previously derived formalisms for extinction are extended to include crystals of non-spherical shape and anisotropy of mosaic spread and particle size. Expressions derived for extinction in an ellipsoidal crystal are compared with numerical calculations on a polyhedral specimen. A pseudo-spherical approximation for polyhedral crystals is described which is accurate to within 2% of the extinction factor y for crystals whose ratio of maximum and minimum dimensions is less than two. Anisotropy of mosaic spread is introduced in both the Coppens-Hamilton (C.H.) and Thornley-Nelmes (T.N.) descriptions, with both a Lorentzian or a Gaussian distribution function. The formalisms are applied to neutron data sets on LiTbF4 (100°K and 300°K), tetracyanoethylene and LiOH. H2O, and an X-ray data set on α-deutero oxalic acid dihydrate. The distinction between type I and type II crystals is quite clear on the basis of a …