Batse all-sky search for transient gamma-ray lines between 300 and 550 keV

We present an all-sky search for bright, transient emission lines from 300 to 550 keV in more than two years (1993 December and 1996 March) of data fr om the Burst And Transient Source Experiment (BATSE) on the Compton Gamma-R ay Observatory. Our approach is sensitive only to events with durations fro m 0.5-3.0 days. The results show that the gamma-ray sky is very "quiet" in these two years, which is consistent with an earlier search using BATSE dat a from 1991 to 1993. No transients are observed in the search, and our 3 si gma upper limits are significantly below the fluxes of the two most signifi cant events previously reported from Nova Muscae and 1E 1740.7-2942 by SIGM A. The disagreement between the BATSE data sets and those of SIGMA are quan titatively discussed.