  We present the discovery of photometric variations in the carbon-dominated
atmosphere (hot DQ) white dwarf star SDSS J133710.19-002643.6. We find evidence
for two low-amplitude, harmonically-related periodicities at 169 s and 339 s,
making it the fastest and smallest amplitude of the four known hot DQ variables
and the only variable whose spectrum suggests the presence of hydrogen. The
star's fundamental and harmonic amplitudes are roughly equal, and its pulse
shape is similar to the other two members of the class with detected harmonics.
Like the other variables, it appears relatively stable in frequency and
amplitude.
