Correlated bursts of bremsstrahlung X rays and VLF emissions were recorded for ~25 min at Siple Station, Antarctica, on January 2, 1971. The burst occurred quasi-periodically with spectral power predominantly in the period range 4--12 s. A typical VLF burst consisted of 3--5 rising elements of ~0.1-s duration separated by ~0.15 s and was confined to the frequency range 1.5--3.8 kHz. Evidence is presented to show that the bursts were triggered by the low-frequency tail of whistlers propagating from the northern hemisphere. The spectrum of the precipitated electrons was characterized by an e folding energy of 45 keV; electrons with energies between ~70 and 250 keV were the primary contributors to the observed X ray flux. A characteristic feature of the data was a time delay of ~0.2 s between the reception of a VLF burst and the associated X ray burst. Calculations show that this delay can be related to the difference in wave and particle propagation times from a burst generation region near the equator to the detectors at Siple Station if the waves and electrons leave the interaction region in opposite directions. The interpretation of the observations in terms of an equatorial cyclotron resonance interaction occurring at the outer edge of the plasmapause on the L=4.2 field line, offered initially by Rosenberg et al. (1971), is given further support by the more extensive analysis presented here of the electron energy-wave frequency relationship in the bursts and the propagation times for the resonant waves and electrons. It is inferred from the X ray data that the equatorial flux of trapped electrons was probably anisotropic and near the stable trapping limit at the time of this event. It is suggestd that an important effect of the trigger signal is the increase of the anisotropy of the resonant electrons. Wave growth rates calculated in the random phase approximation for electron pitch angle distributions that might apply in this event can explain certain features of the VLF and precipitation data during and between the bursts.