They make your derriere look like an apple instead of a ham sandwich," says pomaceous Julie Newmar of the pantyhose she has just patented. "It's a simple improvement. I just gathered the back seam. But it gives a woman the firm fanny of a 12-year-old."

For those women with other worrisome parts, the statuesque actress (5'11", 37-23-37) also has invented a Marilyn Monroe-type bra, which is nearly invisible, and a pantyhose belt for tall women, which "keeps the crotch from sagging to the knees."

Such bursts of creativity are in character for Julie, 41, who boasts a near-genius 135 IQ and is the daughter of an ex-professor of engineering. (Her mother was a Ziegfeld Girl.) She also has a younger brother with a Harvard Ph.D.

Julie has long designed her own clothes. The pantyhose, which she hopes to retail at $4 under the name "Nudemar," were invented out of necessity. "I have two drawers of pantyhose," she complains, "but I don't like what they do for my backside."

"Nudemar" took two years to develop. It is made from a stretchable Monsanto fabric with an elastic back seam that separates the buttocks. "The hips look smaller," Julie explains. "Instead of flattening the fanny, they round it."

The Newmar legs, 37 inches long, have provided the underpinning for a career that began at 15, when she danced with the L.A. Opera Company. Later she scored on Broadway in Silk Stockings and Li'l Abner and as Cat woman on TV's Batman. In 1959 Julie won a Tony for best supporting actress in The Marriage-Go-Round.

Unmarried, she lives in New York, attends five ballet classes a week and almost as many parties, lunches on carrot juice laced with papaya, yogurt and vitamins, reads history and philosophy, and is an outspoken liberal Democrat.

She may next turn her inventive bent to men's pajamas. "They all have a terrible cut," she laments. "I can't get any to fit me."