Polished equatorial sections of Foraminifera, embedded in polystyrene, are scanned with an electron beam focused into a 1-micron spot. Some electrons are backscattered from the specimen, amplified, and displayed on a cathode ray tube. Electrons which enter the specimen excite X-rays, which are collected by a crystal spectrometer that can select the characteristic emission from an element in the surface of the specimen. The X-ray image, displayed on a cathode ray tube, shows the distribution and concentration of the element. Interpretation of backscattered electron images and X-ray images is complicated by topographic and microstructural effects that reduce their usefulness. Modifications to improve magnesium detection are suggested. Examination results on five species are reported.

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