A MISSING BUNDLE of half-million year-old bones remains one of the tantalizing usolved archeological mysteries of all time. The assorted fossil fragments of Peking Man, a low-browed creature whose unprepossessing appearance belies his scientific importance in the search for man's beginnings disappeared on the eve of Pearl Harbor in the havoc of the Japanses invasion of China.

When last seen, the bones were neatly packed in two redwood chests for a Marine-guarded transfer to the United States. A classic whodunit, this scientific mystery is fraught with incredible melodrama: the anthropological find in limestone caves; the mysterious disappearance, foreign intrigue : and an untiring detective chase over more than three decades.

Now Claire Taschdjian, the young assistant who packed the bones in the chests, has written a fascinating fictional reconstruction in The Peking Man Is Missing (Harper & Row. $10). It is a convincing tale of what might well have happened, and one of the more unusual and original mysteries in a long time, despite some awkward moments.

No mystery writer could concoct a more intriguing plot, background and cast of characters than real life has given Taschdjian. There is Peking in the hectic days of the Japanese invasion - with American Marines, Red Chinese spies as houseboys, foreigners in the Legation Quarter, and dedicated scientists X raying and interpreting old bone fragments as the world blows up around them. (Pierre Teilhard de Chardin, the Catholic philosopher-scientist, becomes the Father Lorrain of the novel.) Then there is the scientific treasure-hunt for the bones by Japanese, Red Chinese and American intelligence officers as Peking Man becomes both a symbol of national pride and a diplomatic ploy.

Taschdjian tells the story of Kathy Ewers, the naive young daughter of Swiss-German medical missionaries. After their death, she stays on to work at the Paleoanatomy Laboratory in Peking. One of her friends is Evvie Zunmerman, married to an American wheeler-dealer whose bedroom chemistry experiments produce drugs to suport the couple's high-living style. Kathy, an innocent, takes Evvie's husband and a Marine buddy on a tour of the lab to look at the famous fossils. The two couldn't care less about old bones and scientific value, but they can see a million-dollar ransom in hijacking the Peking Man.

The pieces of the reconstruction dovetail neatly in the rush of events - the Japanese unvasion, the planned transfer of the fossils to a Marine base, the explosion in the bedroom lab and the death of Evvie's husband occupation by the Japanses, and internment of American prisoners of war. It might well have happened.

The street scenes of Peking are filled with the sights, smells and sounds that Taschdjian experienced first-hand in her years there - the flutelike piping of reed whistles tied to the tail feathers of pigeons, the chants and clappers of street venders, the spicy aroma of food mingled with the smell of dust, open Sewers, camel dung and incense. And she conveys what it was like to live under Japanese rule, with each foreigner wearing a distinctively-colored armband to identify him as an Axis ally, neutral or enemy.

The story is so fascinating that it survives shortcomings in Taschdjian's storytelling skills. Too often she falls back on dull exposition ("Walking backward toward the Legation Quarter, Kathy found out more about the two Marines," followed by a liferesume that should have been captured better in revealing dialogue.)

The lives of Kathy, Evvie and the others from wartime Peking cross again two decades later in 1960 when the body of a strangled middle-aged woman stuffed in a plastic leaf bag) is found by two birdwatchers in the swamps of the Jamaica Bay Wildlife Refuge. There is no one to idnetify Evamarie Zimmerman Alveez, the China-born German widow of a Cuban diplomat. And there are other mysterious legacies of the '40s. An ex-Marine of the UN staff is killed in a car crash, a Red Chinese defects, and a German frau sorts through mementos of her young days in Peking.

And what finally happened to the bones of the Peking Man? Read Claire Taschdjian's novel. Or read the newspapers. Only two years ago, Peking Man was in the headlines again. Arabbit-hunting soldier, claiming a $150,000 reward, told of stumbling on a foot locker full of bones, covered with the red dust of China, in an abandoned cabin in the California woods. It was a false lead. The $150,000 offer still remains, and Peking Man scientific sleuths still want to go to China in hopes that some one may have picked up bones discarded by Japanese soldiers rifling through Marine foot lockers.

So the mystery of Peking Man still remains - if Taschdjian's tantalizingly plausible reconstruction isn't true.