  Using photometric selection criteria, and in a final step visual inspection
of spectra, we find 65 DQ white dwarfs in the Data Release 4 of the Sloan
Digital Sky Survey. 37 of these are new identifications, three more are
reclassified DQ from DC, the other 25 have been described as DQ before in the
literature. We derive effective temperatures and carbon abundances for 60 of
these stars. The results confirm the main conclusions of Dufour et al.(2005).
The majority of stars defines a clear sequence in the C abundance vs. Teff
diagram, with high abundances found at high Teff and vice versa. We also
confirm with high significance a second sequence with an abundance about 1 dex
higher at the same Teff, and discuss the nature and possible origin of the
high-C sequence.
