  IC 2163 and NGC 2207 are interacting galaxies that have been well studied at
optical and radio wavelengths and simulated in numerical models to reproduce
the observed kinematics and morphological features. Spitzer IRAC and MIPS
observations reported here show over 200 bright clumps from young star
complexes. The brightest IR clump is a morphologically peculiar region of star
formation in the western arm of NGC 2207. This clump, which dominates the
Halpha and radio continuum emission from both galaxies, accounts for ~12% of
the total 24mu m flux. Nearly half of the clumps are regularly spaced along
some filamentary structure, whether in the starburst oval of IC 2163 or in the
thin spiral arms of NGC 2207. This regularity appears to influence the clump
luminosity function, making it peaked at a value nearly a factor of 10 above
the completeness limit, particularly in the starburst oval. This is unlike the
optical clusters inside the clumps, which have a luminosity function consistent
with the usual power law form. The giant IR clumps presumably formed by
gravitational instabilities in the compressed gas of the oval and the spiral
arms, whereas the individual clusters formed by more chaotic processes, such as
turbulence compression, inside these larger-scale structures.
