  By image processing and color excess analyses of B, V, R, and I-band CCD
images of the central region of M31 taken with the Kiso 105-cm Schmidt
telescope, we found a bar of 200 pc length. We also found a more extended
``face-on" spiral feature of dark clouds, which appear t o be connected to this
bar and is probably an out-of-plane structure. The \co-line emission was
detected from the dark clouds using the Nobeyama 45m telescope, and the virial
mass of individual clouds was estimated to be about 10E6 solar masses. The CO
intensity-to-virial mass ratio is anomalously small, and so is the color
excess-to-mass ratio, which indicates a low temperature and a small amount dust
per unit gas mass in the cloud, respectively. This implies that the molecular
clouds in the central few hundred pc of M31 are more primeval, suggesting a low
star-formation and low dust supply. We propose a possible scenario for the
origin of the face-on spiral containing such gas on the basis of a ram-pressure
accretion model of stripped gas clouds from the companion galaxies. Key words:
Dark clouds -- CO line -- Galaxies; individual (M31) -- Interstellar dust --
Nuclei of galaxies.
