  We investigate the three-dimensional structure of the so-called ``200-pc
expanding molecular ring" in the Galactic Center by analyzing (b, Vlsr)
diagrams of the 13CO(J=1-0) line emission from the Bell-Telephone Laboratory
survey. We show that the b-v features can be fitted by a spheroidal shell
pinched at the equator (dumbbell-shaped shell), which we call the expanding
molecular shell (EMS). The radius is about 180 pc and the vertical extent is
more than +/-50 pc. The shell is expanding at 160 km/s, and is rotating at 70
km/s. The association of the radio continuum emission indicates that the EMS is
a mixture of molecular and ionized hydrogen gases. An extended hot (X-ray)
plasma appears to fill the interior of the shell. The estimated molecular mass
of the shell is approximately 1.E7 Msun and its kinetic energy 2.E54 ergs.
