We report the detection of CO ($J$=3$to$2) line emission from all three multiple images (A,B and C) of the intrinsically faint ($simeq$ 0.8 mJy) submillimeter-selected galaxy SMM J16359+6612. The brightest source of the submm continuum emission (B) also corresponds to the brightest CO emission, which is centered at $z$=2.5168, consistent with the pre-existing redshift derived from Ha. The observed CO flux in the A, B and C images is 1.2, 3.5 and 1.6 Jy kms respectively, with a linewidth of $500pm 100$ kms. After correcting for the lensing amplification, the CO flux corresponds to a molecular gas mass of $sim 2times 10 ^{10} h_{71}^{-2}$ Msun, while the extent of the CO emission indicates that the dynamical mass of the system $sim9times10^{10}$ Msun. Two velocity components are seen in the CO spectra; these could arise from either a rotating compact ring or disk of gas, or merging substructure. The star formation rate in this galaxy was previously derived to be $sim$100--500 Msun yr. If all the CO emission arises from the inner few kpc of the galaxy and the galactic CO-to-H$_2$ conversion factor holds, then the gas consumption timescale is a relatively short 40 Myr, and so the submm emission from SMM J16359+6612 may be produced by a powerful, but short-lived circumnuclear starburst event in an otherwise normal and representative high-redshift galaxy.
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