These may or may not form a homogeneous physical class; indeed, some spectral differences are already indicated.'% e shall, as a matter of prudence, exclude the strongest source, Scorpius, from the present considerations be-cause (i) it is apparently so much brighter than the rest, and (ii) it lies at relatively high ga-lactic latitude (-+ 25'). These properties suggest that the x-ray source in Scorpius, which we denote by Sco XR, is much closer than the typical source, and may radiate by a different mechanism, one intrinsicallyso weak that it would be unimportant for the others. In a sim-ilar spirit we shall exclude the one to five sources which lie in the direction ofthe galactic center, at Sagitarius A, on the grounds that the galactic center also may hold a distinct kind of phys-ical object.'Both these exclusions are, of course, merely tentative. Some half-dozen sources remain. The posi-tive identification of Tau XR (Tau denoting Taurus) as the Crab nebula, SN 1054 (SN stand-ing for" supernova"),~ and the possible identi-ty of Oph XR (Ophiuchus) as Kepler's nova,