NGC 4485 and NGC 4490 are closely interacting spiral galaxies in the N
GC 4631 Group, separated by a projected distance of 7.7 kpc. Images in
the B and I bands were obtained with the Burrell Schmidt telescope at
Kitt Peak National Observatory in order to study star-forming regions
in their tidal features, including a previously undetected faint tail
whose color matches that of the outer disk in NGC 4490. A comparison
of the tidal morphology with published simulations suggests that this
is a prograde encounter with perigalacticon about 4 x 10(8) yr ago. Th
is time is approximately the age of the youngest regions in the tail,
based on a comparison of observed B-I colors with evolutionary models.
Calculations of the Q instability parameter using a rotation curve de
rived from published H I observations support the conclusion that the
tail is currently stable against star formation.