NEW HAVEN, May 16--Harvard today gained a share of the Ivy League Lacrosse Championship for the first time in history, but needed help from Dartmouth to do it.

Playing without defenseman Fred Gates, a tense and listless Crimson team was soundly beaten by Yale, 9-6, and ended the Ivy season with a 4-2 record.

Princeton finished with an identical record, however, suffering its second defeat, 7-5, at Hanover. Dartmouth can make it a three-way tie by whipping sixth-place Cornell next week.

The Crimson defense was hurting without the speedy Gates, who pulled a hamstring muscle in practice yesterday. Yale's small but manueverable attack dominated play for most of the game and shot almost at will.

Captain Demi Gibson scored three goals and an assist, while Mac Bradford got a goal and three assists to lead the Elis.

Midway in the second period Joe Barton scored for the Crimson to tie the game at 3-3, but his goal failed to ignite a rally

Bradford scored for Yale at 9:04, and 15 seconds later Brian Rapp slammed a Gibson feed past Orm Hammond. Gibson tallied at 13:22 to give Yale a 6-3 halftime edge.

Wally Whitney dislocated his shoulder early in the second half, and his loss broke up the Crimson's smooth-working second mid-field. Events took a further turn for the worse when Gibson scored again at 5:34.

Dick Ames rushed the Yale goal but several point-blank shots only ricocheted off Don Ogilvie, Tink Gunnoe managed a goal at 9:32, but 17 seconds later the irrepressible Gibson scored again and Harvard was just about through.