British Transport Police have released a CCTV image after a man was bitten on the nose at Oxenholme station in Cumbria.
The incident happened at 10.20pm on Friday 13 December.
The victim, a man in his 30s, was bitten after having a conversation with the suspect. He suffered cuts and bleeding.
Officers believe the man in the picture may have information that could help their investigation.
Anyone who witnessed the incident is asked to contact BTP by texting 61016 or by calling 0800 40 50 40 and quoting reference number 13 of 14/12/19.