shipped for radioanalysis. A summary of 239, and 241an tissue burdens in vertebrates of NAEG study areas is contained in the last formal report (Bradley and Moor, in press). Few additional data were available for analyses to include in this report. Although many data await further analysis, certain trends appear evident and discussion appears justifiable. Table 2 presents 239 Pu and 241 Am tissue burdens in D. microps from three study areas of NTS and TTR. here. An interesting trend is indicated Whereas Pu/Am ratios are variable in tissue samples, they are significantly lower in the carcass than in the pelt or GI tract (P > .05) of animals collected in the three study areas. For example, D. mierops from Clean Slate 2 had significantly higher ratios (P > .01) in the pelt (27.6) and GI tract (18.2) than in the carcass (9.4). Preliminary results suggest preferential Am uptake is evident in rodents. Conversely, ably uniform. the skin, Pu/Am ratios in tissues of lizards were remark- Nine lizards from Area 11 had Pu/Am ratios of 6.85 in 6.81 in the GI tract, and 6.85 in the carcass. There are several possible explanations for the differences in Pu/Am ratios in lizards and rodents. vores, The rodents examined thus far have been grani- the lizards insectivorous. Romney et aZ. (1974) indicate that preferential uptake and concentration o £ 241an through plant roots might have occurred in Area 13. Whereas the Pu/Am ratio is somewhate higher in vegetation than in animal tissue in Area 13, no data could be found on the distribution of Pu and Am within tissues and organs of individual plants. Additionally, no data on Pu and Am tissue burdens in insects could be found. These data should be available before further analyses of trophic transfer can be properly evaluated. Fowler and Essington (1974) indicated that Am is moving faster downward in the soil than Pu. Because rodenty in general are more or less fossorial and lizards are not, perhaps Am is more available to rodents in the microhabitat of their burrows. The decrease in Pu/Am ratios may be explained on the basis of differential solubilities, and Am may be more available for absorption in the more advanced digestive tract of rodents. 58