  We present the results of mapping observations toward a nearby starless
filamentary cloud, the Taurus Molecular Cloud 1 (TMC-1), in the CCS(JN=43-32,
45.379033 GHz) emission line, using the Nobeyama 45-m telescope. The map shows
that the TMC-1 filament has a diameter of ~0.1 pc and a length of ~0.5 pc at a
distance of 140 pc. The position-velocity diagrams of CCS clearly indicate the
existence of velocity-coherent substructures in the filament. We identify 21
substructures that are coherent in the position-position-velocity space by eye.
Most of the substructures are elongated along the major axis of the TMC-1
filament. The line densities of the subfilaments are close to the critical line
density for the equilibrium (~17 Mo/pc for the excitation temperature of 10 K),
suggesting that self-gravity should play an important role in the dynamics of
the subfilaments.
