Dallas police officers evidently seized more incriminating photographic evidence against Lee Harvey Oswald than they ever supplied to the Warren Commission, the House Assassinations Committee was told yesterday.

The missing evidence, particularly two negatives showing Oswald holding a rifle in one hand and copies of the Militant and the Worker publications in the other, has for years shored up the contentions of critics that the photos the commission did get were fakes.

A panel of phtographic experts assembled by the House committee reported yesterday, however, they had now collected enough original prints, showing Oswald in three different poses to establish their authenticity.

One of the experts, Sgt. Cecil W. Kirk of the metropolitan police department here, said the finding that the pictures all came from Oswald's Imperial reflex camera was shored up by a chance discovery he made at the National Archives only last Sunday.

It was an 8-inch by 10-inch Dallas enlargement of one of the original police shots. According to Kirk, tests have established that the blow-up was made directly from one of the negatives that Dallas police found among Oswald's possessions on Nov. 23, 1963, the day after President Kennedy's assassination.

The negative is missing. But the enlargement, with the official rubber stamp of the Dallas Police Department imprinted on the back, shows that the Warren Commission erred in reporting that the negative was "never recovered."

Kirk, who supervises the D.C. police department's mobile crime laboratory and photographic services unit, also gave low marks to the police procedure involved. He said Oswald was shown the blow-up, rather than the smaller original, which he had seen before.

This, Kirk suggested, gave Oswald an opportunity to denounce it ass a fake, which he did under interrogation at Dallas Police Headquarters on the nith of Nov. 23.

"Why give a suspect an enlargement if you've got the original?" Kirk added during testimony. "It seemed to me to be kind of strange." To reporters, during a break, he added, more succinctly, "I thought it was kind of dumb."

The testimony came near the end of a busy hearing that started with a final round of questioning for Oswald's widow, Marina, and paused in midafternoon for a House floor vote on a $790,000 request to keep the inquiry going until the end of the year.

The House handed the committee the money on a voice vote after a series of speechs praising Chariman Louis Stokes (D-Ohio) for putting the investigation in order after a shaky beginning. Rep. Robert E. Bauman (R-Md.) protested that the committee has already spect $4.5 million in the past two years, making it "the most expensive investigation in the House's history, including the impeachment investigation." But other former critics of the insuiry said they could not justify closing it down in the midst of the public hearing.

Concluding her testimony, the formers Mrs. Oswald, now Marina Porter, finally conceded to the committee that she thought Oswald had killed the president. She had refused to answer that question Wednesday.But she relented after Rep. Christopher J. Dodd (D-Conn.) reminded her that she had said as much to the Warren commission 14 years ago.

Porter said she thought Oswald acted alone and not, in her judgement, for any coherent political reason. "I don't think anybody in his right mind could commit a crime like that," she told the committee. Oswald, she agreed under questioning by Rep. Richardson Preyer (D-N.C.), probably wanted to make himself "important by killing someone important."

Porter told the committee that she snapped the photos of Oswald with his rifle, and a holstered pistol, at his insistence in the spring of 1963 in the back yard of their Neely street home in Dallas. She said she couldn't remember how many pictures she took, whether two or three, and only vaguely recalled his saying something about sending a copy to the Militant.

After the assassination, she burned two prints she found in her daughter June's baby book. She told the committee it never occured to her to look around for the negatives.

Dallas police evidently found three negatives and at least two prints. The Warren Commission got only two prints and only one negative. Besides the traces of the one Sgt. Kirk uncovered, the evidence of another negative having been seized by police was obtained by the committee from two other sources.

Original copies of this pose, never seen by the Warren Commission, were given to the committee by the widow of Dallas police officer Roscoe White and by former Dallas police detective Richard S. Stovall, one of those who conducted the search. The negative is missing, but Kirk said the prints, like all the others, show the unique "signature" of scratch marks and indentations made by Oswald's camera.

Another large print of one of the photos, obtained last year from the widow of Oswald's onetime benefactor, George de Mohrenschildt, was subjected to handwriting analysis. Inscriptions on the back included in one corner a notation saying, "For my friend George from Lee Oswald," with an obscure date "5/IV/63." At the top, in printed Russian letters, were the words "Hunter of fascists - ha, ha, ha." Finally, at the bottom right corner, in printed letters, was the note: "Copyright G de M."

De Mohrenschildt, who was in Haiti at the time of the JFK assassination, committed suicide in March 1977. He had left Dallas for Haiti in May 1963, shortly after Oswald's attempted assassination of Gen. Edwin Walker (U.S. Army, Ret.)

There has been speculation that Oswald's wife jotted down the mocking note above Oswald's purpoted inscription, perhaps to chide her husband for the Walker incident. She told the committee that the sarcastic "hunter of fascists" line sounded like something she would have written, but the handwriting was not hers.

Handwriting expert Joseph P. McNally agreed that it was not her writing. But he told the committee that the Russian words had apparently been traced over an original, perhaps similar inscription after it had faded or been erased.