Normalized spectrum of a representative B: star, as observed with Hectospec’s 600 lines mm⁻¹ (lpm) grating. Relevant spectral features are marked as in Figure 7. The B: sources cannot be classified using the wavelength range shown in Figure 7 because their 270 lpm spectra are overly noisy or they are heavily extincted in the blue. Consequently, we were unable to determine precise spectral types for these sources, although their He I absorption lines identify them as B-type (or possibly late O-type) stars. Most of the unmarked features in this spectrum are of interstellar or atmospheric origin.