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We made VLA HI observations of the young, interacting galaxy pair NGC 2535/36 in C and D Arrays (resolution = $12''$ = 2.9 kpc). NGC 2535 has an "ocular" structure similar to that in IC 2163, which we studied previously. In NGC 2535, the intrinsic HI velocity dispersion is high, 30 km s$^{-1}$ over much of the disk, as compared to less than 10 km s$^{-1}$ in undisturbed spirals. The tidal arms of NGC 2535 contain five unusually massive clouds, with HI masses exceeding $10^8 M_{\sun}$ and radii = 2 -- 3 kpc. These masses are comparable to the masses of HI-rich dwarf galaxies. Most of these clouds do not have prominent counterparts in the older stellar population. The HI column densities and velocity dispersions in these clouds imply a Jeans mass close to the observed HI cloud mass; the high gas turbulence apparently leads to the large cloud mass as a result of gravitational instabilities in the gas. Elmegreen et al. (1993, ApJ, 412, 90; 1995, ApJ, in press) found similar widespread high gas turbulence and very massive HI clouds without strong stellar counterparts in the young interacting pair IC 2163/NGC 2207. This suggests that enhanced turbulence and unusually massive gas clouds produced by gravitational instabilities in the gaseous disk may be a general feature of interacting spiral galaxies during the early phases of post-encounter evolution. The massive HI clouds in NGC 2535, IC 2163, and NGC 2207 give observational support to the gravitational instability model in Elmegreen et al. (1993, ApJ, 412, 90) and are not predicted by the Barnes and Hernquist (1992, Nature, 360, 715) model for the formation of tidal dwarf galaxies.
