Bone fragments ranging in age from Late Cretaceous to Pleistocene have been analyzed for heavy elements by X-ray emission spectrography. Common elements in bone are Fe, Sr, Y, Mn, Ba, and As, while U, Pb, Sb, Sn(?), La, and In are occasionally present. Of these, Fe, Sr, Mn, As, and possibly Y show systematic variation in distribution by age. Fe shows a general trend of increased concentration with increase in age. Mn is generally restricted to the stratigraphic levels below the Middle Oligocene while As is restricted to certain parts of the Late Tertiary. Sr and Y, though generally present show maxima at certain stratigraphic intervals. These data seem useful for approximate determinations of stratigraphic level within the area studied.