The Iphigenia of Euripides' tragedy "Iphigenia at Aulis" is one of the noblest heroines in dramatic literature, and perhaps the noblest of juveniles. Summoned to the port of Aulis, where the Greek fleet restlessly awaits favorable sailing weather to Troy, the princess discovers that she has been deceived for reasons of state by her father, Agamemnon.

Persuaded by a seer that the sacrifice of his eldest, favorite child will appease the gods and bring fair breezes and fearing the enmity of his own allies if he should resist the prophecy. Agamemnon has lured Iphigenia to her doom with a false promise of marriage to Archilles.

The revelation of this betrayal kindles a murderous hatred in Iphigenia's mother, Clytemnestra, that will smolder for 10 years and cause her to conspire to kill her husband upon his return from the Trojan War.

Iphigenia, on the other hand, recovers from her immediate shock and despair to accept a cruel fate with heartbreaking fortitude and generosity - a response that make her victimization seems all the more painful and shameful.

The play is believed to date from about 405 B.C., near the end of Euripides's life. His son appended an ending in which Iphigenia was snatched from the funeral pyre at the last moment. Micheal Cacoyannis' somewhat attenuated yet impressively acted movie version of the play, "Iphigenia," now in its first American engagement at the West End Circle, rejects the "happy" ending, although Cacoyannis is not above pretending that Agamemnon might have a cliff-hanging change of heart and redeem himself as a father, a moment too late.

Best known for "Zorba the Greek," Cacoyannis filmed adaptations of "Electra" in 1962 and "The Trojan Women" in 1972, so "Iphigenia" completed his intended Euripidead trilogy. Actress Irene Papas has been a magnificient presence in all three movies.

She had her first international success as Electra, a younger daughter of Agamemnon and Clytemnestra. In "The Trojan Women" she appeared briefly as the captive Helen, the aunt of Electra and Iphigenia and, of course, the pretext for the Trojan War. In "Iphigenia" she portrays the proud, srticken Clytemnestra, enraged at her husband for sacrificing their child.

The play is swift and incisive, as effective as a short knockout punch. Cacoyannis, shooting on location in Athens and Corinth, where he enjoyed the use of 5,000 Greek Soldiers for a day, has tried to expand the text with sweeping pictorial vistas and crowd scenes, as well as the addition of a few characters Euripides had kept in the wings, notably Odysseus.

I did not feel that this embellishments improved the text, but I saw the film in an exhausted mood, and it wouldn't surprise me if Cacoyannis had made the play more accessible to many people by pumping it up pictorially.

Still, his finest pictorial subjects also happens to be his leading actresses, Papas as Clytemnestra and a radiantly nonprofessional Tatiana Papamoskou, who was 12 when she portrayed Iphigenia two years ago. My wandering attention seemed to return in a flash whenever Papas or Papamoskou dominated the scene.

A tall, slender, strong-featured girl who projects Iphigenia's apprehension and resignation with a beautiful simplicity and sincerity, Papamoskou seems a noble figure of a child in her own right. Her physique and plaintiveness recalls Audrey Hepburn to some extent - enough to make one wish that there were a decent enough mother-and-daughter story to justify co-starring them. She and Papas are no run-of-the-mill combination in "Iphigenia."

Even if Papamoskou never makes another picture, the poignancy of her best scenes, especially the moment when she pleads, according to the subtitles. "Mother, I'm trying to be brave; help me."