  We report the results of mapping observations of the bipolar nebula with SiO
maser emission, IRAS 19312+1950, in the CO (J=1-0 and J=2-1), 13CO (J=1-0 and
J=2-1), C18O (J=1-0), CS (J=2-1), SO (J_K=3_2-2_1) and HCO+ (J=3-2) lines with
the Berkeley-Illinois-Maryland Association array. Evolutional status of this
source has been evoking a controversy since its discovery, though SiO maser
sources are usually identified as late-type stars with active mass loss. In
line profiles, two kinematical components are found as reported in previous
single-dish observations: a broad pedestal component and a narrow component.
Spatio-kinetic properties of a broad component region traced by 12CO lines are
roughly explained by a simple spherical outflow model with a typical expanding
velocity of an AGB star, though some properties of the broad component region
still conflict with properties of a typical AGB spherical outflow. A narrow
component region apparently exhibits a bipolar flow. The angular size of the
narrow component region is spatially larger than that of a broad component
region. Intensity distribution of the CS emission avoids the central region of
the source, and that of an SO broad component emission exhibits a small feature
peaked exactly at the mapping center. According to the present results, if a
broad component really originates in a spherical outflow, an oxygen-rich
evolved stellar object seems to be a natural interpretation for the central
star of IRAS 19312+1950.
