I am grateful to M. Hedlund and S. Ohlsson (Stockholm) for help with the original photographic setup and to J. Bergström (Stockholm), G. Budd (Uppsala), D. Collins (Toronto, Ontario), E. Cole (Delta, Utah), T. Denk (Stockholm), L. and F. Gunther (Brigham City, Utah), L. Holmer (Uppsala) and Hou Xianguang (Nanjing) for loans and for helping to locate specimens in private and museum collections. D. Collins kindly drew my attention to previous usage of crossed nicols in Burgess Shale photography. Review comments by N.C. Hughes (Riverside, California), N. MacLeod (London), and two anonymous referees were most helpful for the final revision of the manuscript. My work is financially supported by the Swedish Natural Science Research Council (grants G 650-19981507 and G 5103-1199).