The surging Crimson lacrosse team converted a few more believers yesterday by slogging through the mud past the Dartmouth stickmen, in an overtime victory, 7-5, in Hanover, N.H.

The ten held a 4-1 lead going into the fourth quarter, but middy Scott Anderson and attackman Kirk Hinman, with two goals apiece, spearheaded a Big Green rally to tie, at 5-5, with three minutes to play. In two four-minute overtime periods, however, Harvard scored twice to secure the triumph, the third--and third consecutive--win for the lacrossemen against nine losses.

"We were definitely a better team. In overtime we out-hustled them and had a psychological advantage: we knew we would win," middy Bob Frisbie, who scored three points, said last night.

The Crimson played to a first-quarter scoreless standstill, but in the second period, attackman Steve Milliken, at 7:48, and Frisbie, less than a minute later, scored to give Harvard a 2-0 edge.

The Green's Anderson, who turned the hat trick, got his first goal with 20 seconds gone in the third quarter. Hagerty, unassisted, and middy Rick Carey, from Milliken, retaliated within the next four minutes to up the count to 4-1.

In the first five minutes of the final regulation frame, Anderson and Hinman combined for three points to tie. Following Crimson middy Tom Johnson's goal from Hagerty, at 8:20, Hinman deadlocked things again, on an unassisted tally.

However, Frisbie got his gun in over-time, feeding middy Al Costello with 30 seconds gone to make it 6-5. Around seven minutes later, with 46 seconds remaining in the second extra stanza, Frisbie iced it with a tally, on an assist from attackman Jim Quinn.

The lacrossemen outshot Dartmouth, 46-39; but opportunities didn't come easily. "It was a little wet out there. Guys like Hagerty had trouble working it one-on-one," Frisbie said.

The win vaults Harvard up to a fine position for the fourth playoff slot in New England, barring a loss against Yale at home Saturday.

Meanwhile, Brown virtually wrapped up the New England crown by trouncing second-place UMass, 15-7, yesterday in Providence.

Finally, the Harvard freshmen team cruised from an 11-0 third period advantage to a 14-3 victory over the Green frosh, in Hanover.