Cambridge police were still looking for an unidentified undergraduate who last night assaulted a Belmont resident in the Square after a disagreement over an automobile right of way.

The Belmont resident, whom the police refused to identify, was immediately taken to his home and was placed under observation. His condition was described late last night as "fair" by police attendants.

According to observers, the fracas started about 7:30 p.m. in front of Cahaly's, when the Harvard student pulled out, and just bumped the Belmont man's car. An argument ensued, and the Harvard man reportedly belted the man with a "blunt instrument." He then rushed away.

Police arrive shortly afterward, and after a quick investigation took the man to his Belmont residence, where he was placed under observation.

According to a Cambridge desk sergeant, patrolmen were out on the streets last night looking for the assailant. They reported that the Belmont man was able to give only a brief description of the attacker. The police added that the man was not in a dangerous condition.

According to one policeman, onlookers knew the assailant was a Harvard man because of the way he dressed. But officers either did not have, or were unwilling to give out, a more specific description of the student.