The section of a wave surface and of a ray surface in plane of incidence/reflection (xy) for ordinary (contours green, violet) and extraordinary (contours black, red) waves via a refractive angle for a one particular type of anisotropy (31). As before kxy and kz are wave vectors, sxy and sz are ray vectors. The elongated figures – for an extraordinary wave (30), a circle – for an ordinary wave (28). During construction of sxy and sz contours a real meanings were multiply by three