The surveillance video shows one suspect at the West 14th Street Station in Chelsea.
Police say he was part of a group that assaulted and robbed a man on the 2 train.
They believe the group was also behind two other robberies on the 6 line in the Bronx.
In one case, the robbers pushed the victim off the train at a stop.
The suspect is described as a black male in his 20's, 5'8"-6'0", 170-200 lbs, with black braids, and was wearing a white short-sleeve shirt, and green shorts.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).
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