*********************

Despite extraordinary physical evidence to the contrary, Shirley Jones just turned 70 — and she 'fesses up to that fact cheerfully, without the hint of a wince. "Yes, it's shocking," she laughs, "but I've got to let it roll off my tongue." Actually, it's an easy admission to make if you look exactly the way one would want Laurey ("Oklahoma!"), Julie ("Carousel") and Marian the Librarian ("The Music Man") to look after the girlishness is gone. Shirley did all three in films, of course, achieving something of a royal flush in musical-theatre heroines.

At an age when her contemporaries are clucking over their grandkids' photos, Shirley is in the V.I.P. room deep in the catacombs of the Ford Center for the Performing Arts, reviewing the results of a photo shoot with her and her second-born, Patrick Cassidy, in costume for their roles in 42nd Street. "Doesn't he look presidential?" she beams with Partridge-like pride. "Y'know, he's up for a TV series on the Kennedys. That shot might get him the part. . . . Here, we had some mother-son fun," she says of a picture of her adjusting his tie and him sighing in "Oh, Mom!" resignation.

"There has never been a mother and son together in a Broadway musical before," she insists. "Ever. I would have thought there'd have been more, but they did research and said no. We are the first. All of my confrontation is with my son, which will be fun for the audience."

As Julian Marsh, broken-down Broadway director attempting a comeback, Cassidy finds himself in the odd spot of making Mom mind him. She's Dorothy Brock, difficult Broadway diva prone to flare-ups and flame-outs. Theirs is a rocky road to Broadway — but tuneful. "This is a different kind of singing for me," Shirley says. "It's not the real soprano stuff. Except for 'I Only Have Eyes for You,' it's up and swingy and something I haven't done before. I like the role, too. She's a real sort of bitchy gal, and I love playing those roles."

Can this be Shirley Partridge talking? Exactly, nods Shirley, who professes to prefer the tart and temperamental over the sweetness and light with which she is often associated. Seconding that motion is the Oscar she got playing Lulu Bains, the hussy Elmer Gantry sent hurtling into a life of rack and ruin after he deflowered her behind the pulpit. It was one of her few times out of calico.

Broadway last saw Shirley 35 years ago (all too briefly) as Maggie Flynn. To be sure, there've been offers to return, but none interested her till now. Why now? "To be very honest? Because they asked both of us to do 42nd Street. I'm excited about this because I think that it's a good time for me, it's a good part for me — and I'm working with Patrick."

Not to put too fine a point on it, but Shirley was pregnant with Patrick when she was filming "The Music Man." "I found out about three months into the filming, so I went to the director, Morton DaCosta, and he said, 'Don't worry, Shirley. We'll do everything to help you. Don't tell anyone.' They built a corset for me and added crinoline and flounces, and no one was the wiser — until the footbridge scene, the only love scene in the film. Well, here we are, Bob Preston and I, with our arms around each other, all ready for the great big kiss — then, all of a sudden, Bob opened his eyes and stepped back and said, 'What the heck was that?'" Patrick Cassidy had made his entrance.

Years later, she continues, Preston and Patrick crossed paths at a benefit in New York. "Patrick knocked on his dressing room door and said, 'Mr. Preston, I'm so excited, so happy, to meet you. My name is Patrick Cassidy.' With that, Bob stepped back and said, 'I know, I know. We've already met!'"

Richard Rodgers and Oscar Hammerstein II entered Shirley's life when she was 18, and it's such a Cinderella story it's a wonder they didn't let her play that part as well. Shirley showed up, out of nowhere (Smithton, PA), at an open casting call, and impressed R&H's casting director enough for him to fetch Rodgers, who, in turn, hastily summoned Hammerstein to the scene. A deal was practically struck on the spot.

"I was the only person — one and only, first and last — who was ever put under personal contract to Rodgers and Hammerstein," she says. They immediately inducted her as a nurse in the last months of the original South Pacific. Then they threw her a small-role-with-a-big-song ("No Other Love") in their Me and Juliet, in which she toured to Chicago and took over the lead from Isabel Bigley. It was in Chicago that R&H told her what they had in mind for her all along: playing Laurey Williams in their movie version of "Oklahoma!"

The film's director, Fred Zinnemann, directed her test — with Gordon MacRae playing Curly and Larry Storch playing Ali Hakim — and asked afterward if she'd ever acted for the camera. She said no. "Well, you're a natural. Don't change anything."

It helped, of course, that Shirley came to the movie with a schoolgirl crush on MacRae. "There was a radio show called 'The Teen Timers Club,' and he was on it. That voice got to me when I was 16 years old. I still feel that he was the greatest singer ever, of all time. Then, to get to work with him! And sing with him! It was a dream come true."

But her Dream Curly didn't arrive till R&H sent her to Europe in an Oklahoma! helmed by that show's original director, Rouben Mamoulian. There she met the late Jack Cassidy. Marriage to Cassidy followed and with it three sons (Shaun, Patrick, Ryan), a stepson-turned-TV son (David) and many stage pairings (The Beggar's Opera, The Marriage Band, Wait Until Dark, Maggie Flynn). They divorced in 1974, and for the past 26 years, she has been Mrs. Marty Ingels.

Shirley left Broadway on the arm of one Cassidy and returns on the arm of another.