THE PUZZLING FEATURES OF THE INTERSTELLAR-MEDIUM IN NGC-205

We present CO 1 --> 0 and 2 --> 1 observations of NGC 205, which is a dwarf elliptical galaxy and a companion to M31. It has long been sugge sted that NGC 205 has interacted with M31 in the past. The total mass of gas (molecular, atomic, and X-ray emitting) associated with NGC 205 is similar to 10(6) M-circle dot, which is 1 order of magnitude less than the mass that should have been returned to its ISM by evolved sta rs during its lifetime. A burst of star formation began in NGC 205 sim ilar to 5 x 10(8) yr ago, ending a few million yr ago; while some of t he mass that was returned to the ISM would be used up by the starburst , star formation is a notoriously inefficient process. Moreover, the g as in NGC 205 is rotating, while the stars are not, so any gas returne d to the ISM should have zero net angular momentum. We suggest that th e angular momentum was added when the preexisting gas interacted with an external gas cloud, either in the disk of M31 or, perhaps less like ly, in the region surrounding it. The recent starburst could have been triggered by the interaction, and the blast waves from ensuing supern ovae would then have removed most of the remaining gas. Sufficient tim e has passed since these events for planetary nebulae to have contribu ted most of the gas we see in this galaxy.