Rock Frock

On the evening of Feb. 23, Jennifer Lopez appeared at the Grammys draped in a long sleeved, floor length frock of silk chiffon printed with emerald palm fronds and chartreuse leaves. Beneath this translucent wisp was a built in pair of crystal studded panties, and twinkling above that was a jeweled pin. The pin hovered inches below the navel, marking the height of the skirt's slit and the depth of the neckline's plunge. The house of Versace had designed the dress to be as backless and frontless as the outside bounds of vogue allowed. In short: hubba hubba and hullabaloo.

God -- not to mention Madonna -- knows that we've gazed at our share of skin. Flocks of starlets courted overexposure at other awards shows last year, and in Manhattan (where prosecutors allege Lopez is a gun moll), it was not uncommon for your average investment banker or Latin teacher, taking a cue from HBO's ''Sex and the City,'' to go to dinner looking like a pricey hooker. Hubba hubba but ho hum. Lopez's body politics were of another magnitude. She turned herself out as the fly girl hyperversion of postfeminist power, flaunting her control by toying with the threat of excess. In consequence, her star went supernova.

Valerie Steele, acting director of the Museum at the Fashion Institute of Technology, likens this fuss to a scandal that raged at the Paris Salon of 1884. The painter John Singer Sargent had dared to depict a fallen shoulder strap in his portrait ''Madame X.'' ''Part of it was just that the dress was sexy and worn in a sexy way,'' Steele says. ''But mostly it was that Madame X was known to be an erotic figure.'' ''Madame X'' now hangs at the Metropolitan Museum of Art.

While the Met won't confirm that it desires the Grammy gown for its Costume Institute, people at People are struggling to rustle it up for a fashion exhibit. Right now, though the dress is safe at home in L.A., tawdry rumors shoot around about its present condition. You see, it has slipped off and into legend.