  On the basis of an extensive new spectroscopic survey of Galactic O stars, we
introduce the Ofc category, which consists of normal spectra with C III
\lambda\lambda4647-4650-4652 emission lines of comparable intensity to those of
the Of defining lines N III \lambda\lambda4634-4640-4642. The former feature is
strongly peaked to spectral type O5, at all luminosity classes, but
preferentially in some associations or clusters and not others. The
relationships of this phenomenon to the selective C III \lambda5696 emission
throughout the normal Of domain, and to the peculiar, variable Of?p category,
for which strong C III \lambda\lambda4647-4650-4652 emission is a defining
characteristic, are discussed. Magnetic fields have recently been detected on
two members of the latter category. We also present two new extreme Of?p stars,
NGC 1624-2 and CPD -28^{\circ}2561, bringing the number known in the Galaxy to
five. Modeling of the behavior of these spectral features can be expected to
better define the physical parameters of both normal and peculiar objects, as
well as the atomic physics involved.
