Obsessed with what he considered one of the greatest portraits ever made, Bacon (1909-1992) did about 30 versions of Velazquez's ''Innocent,'' dragging him headlong into the terrible 20th century. '' Study After Velazquez'' and a companion canvas, ''Study After Velazquez II'' (also from 1950), are recently found paintings from the series, long thought to have been destroyed by the artist. They are the centerpiece of ''Francis Bacon: Important Paintings From the Estate'' at the Tony Shafrazi Gallery. The two, never before exhibited, are from a planned group of three canvases, the third of which is unaccounted for.

In the second painting, the howling Pope has become a businessman in a dark suit, one leg crossed over the other, slightly obscured by a boxy curtain of red stripes. At the bottom is a diagrammatic cage, as in Bacon's earlier Pope study, that separates the Pope from the viewer while at the same time inviting entry. Bacon derived the open mouth from such images as the shrieking, wounded nursemaid in Eisenstein's 1925 film ''The Battleship Potemkin'', and the primal scream of a mother torn from her child in Poussin's ''Massacre of the Innocents'' (1630-31), described by Bacon as ''probably the best human cry in painting.'' And possibly he drew from the terrified, whinnying horse in Picasso's ''Guernica'' (1937).

Although presumed lost, nearly 50 years later the two pope paintings turned up in the warehouse of an artists' supplier in London, where Bacon had sent them along with other paintings to have new canvas stretched on their frames. Whether he had given orders to destroy the originals or not, the supplier had saved and stored them. The discovery coincided with the transfer of the Bacon estate, long handled by the Marlborough Gallery in London, to the Shafrazi gallery, a shift that this show celebrates.

The rediscovered ''Innocent'' paintings are the standouts of the exhibition, which includes a dozen other works dating from 1949, the year of Bacon's first one-man show, to 1991. The popes and other angst-ridden canvases of the 1950's, depicting morphed and creepily contorted grotesques that seem to comment on the despair of the war years and after, are the most compelling.

Grace Glueck, New York Times, December 18, 1998