FIG. 1 is a perspective view of a circular lamp housing showing my new design; FIG. 2 is a front view thereof; FIG. 3 is a rear view thereof; FIG. 4 is a left side view thereof; FIG. 5 is a right side view thereof; FIG. 6 is a top view thereof; FIG. 7 is a bottom view thereof; and, FIG. 8 is a cross-sectional view thereof, taken along line 8—8 in FIG. 6.