Racing fans who have been deploring the quality of America's 3-year-olds all spring can sing hosannas today. An authentic star has emerged from this generation.

Ski Goggle, a gray filly from California, turned what was supposed to be a tough battle with Princess Rooney into a runaway in the $115,600 Acorn Stakes at Belmont Park. Leading all the way, she scored a smashing 7 1/2-length victory that handed Princess Rooney the first defeat in her 11-race career.

Ski Goggle ran the mile in 1:35 and paid $7 as the second choice to Princess Rooney, who was sent off at even money. Princess Rooney held on for second, a neck ahead of Thirty Flags.

If Princess Rooney had compiled a record that made her look almost invincible before this afternoon, Ski Goggle has one now. She has not only won all five of her races by a combined margin of 38 1/2 lengths, she has never had a rival in front of her and has never even been seriously challenged.

Because the two favorites in the Acorn are both front-running types, most of the 35,013 people at Belmont Park expected the first leg of the filly Triple Crown series to develop quickly into a head-to-head duel. But the kind of speed that can carry horses to the lead in the East is a lot different from California's definition of speed and those differences were apparent in the first moments of today's race.

As soon as the gate opened, jockey Chris McCarron had Ski Goggle in high gear. She had opened a two-length advantage before Princess Rooney even seemed to start accelerating. As soon as trainer Tommy Doyle saw that, he knew that he had taken a winning gamble. He had spurned relatively easy pickings in California and had come across the country to challenge the champion but, he said, "When I saw her break so alertly I was very confident."

Ski Goggle was permitted to go the first quarter in a leisurely (by California standards) 23 seconds, with Princess Rooney and Far Flying stalking her. As they reached the turn, Jacinto Vasquez reached back and whipped Princess Rooney and she responded, pulling within a length of the leader. This was the moment of truth.

"It was the first time she was ever asked to run," Doyle said. "In all her starts on the West Coast she was hand-ridden."

But as soon as McCarron asked Ski Goggle for a serious response, he could feel the power underneath him. And Princess Rooney saw something she had never seen before: another horse pulling away from her.

Ski Goggle reached the three-quarter mark in 1:09 4/5 and pulled away through the stretch.

It was as unequivocal a result as a horse race can offer and even Frank Gomez, Princess Rooney's trainer, had to acknowledge the truth of what he saw today. "She ran her race," he said. "She just got beat by a better horse."