FIGURE 12. Two specimens of Chancelloria and one of the sponge Vauxia from the Burgess Shale, British Columbia (ROM 49605). Immersed in water. A. Without crossed nicols; green channel. B. With crossed nicols; green channel. C. Image obtained by subtracting the pixel values of B from those of A, using the Adobe Photoshop “Subtract” blending mode (settings: Opacity = 100, Offset = 100, Scale = 1) and subsequently adjusting the levels in the combined channel. D. Image obtained as in C, except that values of A are subtracted from those of B (this has the same effect as inverting the values of C). (Click on the picture to toggle between different views, or select one of the following links: A, B, C, D.)