We have analyzed the rare gases in a CO2 well gas from Harding County, New Mexico, by mass spectrometry. We have reconfirmed the monoisotopic exces of 129Xe measured previously. The excesses of fissiogenic Xe isotopes have relative proportions which coincide with the spontaneous fission Xe spectrum of 238U. No 244Pu-derived, fissiogenic Xe was detected. The uncertainties in the fission Xe component place an upper limit of 20% on the 244Pu contribution to fissiogenic 136Xe. Using this upper limit and the excess of 129Xe, we calculate an upper limit on the formation interval of the earth of 76 m.y. The trapped Ne, Ar, Kr, and Xe are dominated by a component which is similar to that found in mantle-derived terrestrial samples. We also report for the first time an excess of 3He, which is evidence for primordial 3He in the source region of the wall gas.