Few pictures now for sale are more widely suspect than the nearly numberless, meretricious graphics produced late in their long lives by Dali and Chagall.

Earlier this year, six busy New York art dealers -- most of whom provided written guarantees of authenticity -- were convicted for selling nearly $1 million in counterfeit Dali prints. In March, in Honolulu, 17 collectors filed a multimillion-dollar class-action lawsuit against Center Art Galleries, Hawaii, alleging they'd been sold still more Dali fakes. So many are available that neither Sotheby's nor Christie's will now accept for auction Dali prints produced in the past several decades. Bad works by Chagall are comparably common. There are so many fake Chagalls around that Maurice E. Fry, executive director of the International Society of Appraisers, says his society has "no single member {who} will authenticate {recent graphics by} Chagall."

Perhaps it is no wonder that buyers may be leery of "Salvador Dali & Marc Chagall: An Exhibit of Original Works From the Magic World of Two Great Artists," the show that opened Thursday at the Regency Gallery, 739 Eighth St. SE.

Dealer Lewis Fields says his gallery is offering "$2.5 million of original art" brought from Wantagh, N.Y., to Washington by "armored carrier." Lewis adds that Tom Wallace, the Dali wholesaler who provided the show, "has never been touched by law enforcement." The exhibition's catalogue, bound in silver-colored paper, says, "All works of art sold by The Regency Gallery are guaranteed as authentic unless otherwise represented by the Gallery and its staff."

There is one Dali oil on sale, an undistinguished portrait of his wife's nude back. It's priced at $700,000. The Dali graphics go for less. "Tearful Soft Watch" of 1977, a painfully crude version of the motif that made Dali famous in the 1930s, costs only $130,000.

Some of Dali's lithographs, including some on view, were published in editions of as many as 1,000. How much the artist had to do with their publication is a matter of dispute. He often signed blank sheets of paper that were later printed with his images. John Peter Moore, a fomer Dali manager, has estimated that the artist signed 350,000 blank sheets.

One darkish Chagall gouache here, "Wedding" (1952), costs $240,000. It's the best work in the show. And the one closest to his hand.

Of the 15 Chagall prints listed in the catalogue -- they cost as much as $14,000 -- almost all are qualified as either "F/S" or "E/S." The catalogue explains: "Prints marked F/S are facsimile signatures meaning they are plate signed and those marked E/S are estate signed. All are legal ... and do not devaluate the item."

What devaluates this show, what makes the viewer cringe, is the unexpected coarseness of so many of its pictures. Dali (born in 1904) and Chagall (who died at 97 in 1985) were painters of importance -- once -- before they both succumbed to sloppiness and greed. The fakes that flood the market are only partially responsible for their diminished reputations. Both men late in life merely parodied themselves. The exhibit closes Sept. 19.

Stevens at Adams Davidson These are dog days in the galleries. The offerings are slim. But viewers tired of the melting heat may find themselves refreshed by the modest, windswept landscapes of the late W. Lester Stevens (1888-1969) that are now on view upstairs at the Adams Davidson Galleries, 3233 P St. NW.

Stevens had something of a name in the '20s and the '30s. A member of both the National Academy of Design and the American Watercolor Society, he was one of the painters who helped make his home town, Rockport, Mass., a well known colony for artists.

He seems to have admired both Sargent's sunny colors and the brushwork of Ce'zanne. He painted trees and waterfalls, beached boats, covered bridges, and made his pictures on the spot. He must have painted quickly. His wet brush seems to fly. Most of these oils-on-masonite and watercolors-on-paper date from the 1950s, the abstract expressionists' heyday, and some of that time's spirit -- an affection for big pictures, and for the quick attack -- has touched these otherwise old-fashioned scenes. They'll be on view through Sept. 10.