The Discovery of a Long H i Plume near the Peculiar Galaxy NGC 2782 (Arp 215)

I have mapped the peculiar starburst galaxy NGC 2782 (Arp 215) in the 21 cm H I line using the VLA and have discovered a massive H I plume extending ~5' (54 kpc) toward the northwest, containing 1.4 x 10^9^ M_sun_ of atomic hydrogen (~40% of the total H I mass of the system). There is also a shorter H I structure (2') extending toward the east, which contains 6.6 X 10^8^ M_sun_ of H I. In the Arp Atlas photograph, NGC 2782 has a disturbed body with bright arcs, possibly ripples, throughout the disk, and a pronounced stellar tail extending 2.7' toward the east. The eastern H I structure is associated with the beginning of this stellar tail. PDS scanning of the Palomar plates in the vicinity of NGC 2782 reveals a low surface brightness (μ_B_ ~25 mag arcsec^-2^) counterpart to the long H I plume in the northwest. The most likely formation scenario for NGC 2782 is a merger, possibly of unequal mass galaxies, where at least one of the galaxies is gas rich.