f resulting in a density of 1.0. Small samples, spiny lobster hepatopancreas for example, were ashed, dissolved in hydrochloric acid, and sealed in PVC pipe. Oven-dried soil samples were compressed to a density of 1.35 in PVC pipe. Spectrum resolution was done by Schonfeld's of least squares. (1965) method A set of previously prepared reference spectra for the different geometries and radionuclides was used. All values were corrected for decay to the date of collection. The error given for individual values is the 95% error. Strontium-90 Analyses Strontium-90 was determined by measuring the equilibrium concentration of its 90y daughter. Yttrium-90 was separated by solvent extraction and precipitation techniques (Petrow, 1965), with stable yttrium serving as both a carrier and a yield determinant. Recoveries ranged from 80 to 100%. Iron-55 Analyses Iron-55 was separated and purified by a combination of solvent extraction and electrodeposition techniques Beasley, 1967). Recoveries generally exceeded 90%. (Palmer and Counting was done by X-ray spectroscopy with a proportional counter in conjunction with a multichannel analyzer.