  We present results of a survey of CCS, HC$_{3}$N, and HC$_{5}$N toward 40
dark cloud cores to search for "Carbon-Chain--Producing Regions(CCPRs)", where
carbon-chain molecules are extremely abundant relative to NH$_{3}$, as in
L1495B, L1521B, L1521E, and the cyanopolyyne peak of TMC-1. We have mainly
observed toward cores where the NH$_{3}$ lines are weak, not detected, or not
observed in previous surveys, and the CCS, HC$_{3}$N, and HC$_{5}$N lines have
been detected toward 17, 17, and 5 sources, respectively. Among them, we have
found a CCPR, L492, and its possible candidates, L1517D, L530D, L1147, and
L1172B. They all show low abundance ratios of [NH$_{3}$]/[CCS] (hereafter
called the NH$_{3}$/CCS ratio) indicating the chemical youth. Combining our
results with those of previous surveys, we have found a significant variation
of the NH$_{3}$/CCS ratio among dark cloud cores and among molecular cloud
complexes. Such a variation is also suggested by the detection rates of
carbon-chain molecules. For instance, the NH$_{3}$/CCS ratios are higher and
the detection rates of carbon-chain molecules are lower in the Ophiuchus cores
than in the Taurus cores. An origin of these systematic abundance variation is
discussed in terms of the difference in the evolutionary stage or the
contraction timescale. We have also identified a carbon-chain-rich star-forming
core, L483, where intense HC$_{3}$N and HC$_{5}$N lines are detected. This is a
possible candidate for a core with "Warm Carbon-Chain Chemistry".
