  We have used the Submillimeter Array to image, at ~1" resolution, C2H(3-2)
emission from the molecule-rich circumstellar disks orbiting the nearby,
classical T Tauri star systems TW Hya and V4046 Sgr. The SMA imaging reveals
that the C2H emission exhibits a ring-like morphology within each disk, the
inner hole radius of the C2H ring within the V4046 Sgr disk (~70 AU) is
somewhat larger than than of its counterpart within the TW Hya disk (~45 AU).
We suggest that, in each case, the C2H emission likely traces irradiation of
the tenuous surface layers of the outer disks by high-energy photons from the
central stars.
