Art patrons Paul and Bunny Mellon have once again bestowed a massive gift upon the National Gallery of Art, this time marking the gallery's 50th anniversary with a present of 31 original wax sculptures by Edgar Degas as well as 10 Alexander Calder sculptures and the gallery's first Gauguin pastel. The Mellon gifts, along with scores of other 19th- and 20th-century works of art donated in honor of the anniversary, were announced yesterday.

The other works given to the gallery include two Monet landscapes, Albert Bierstadt's recently rediscovered "Lake Lucerne" and pieces by Picasso, Mark Rothko, Barnett Newman, David Smith, Roy Lichtenstein, Jasper Johns, Helen Frankenthaler, Jim Dine and Robert Rauschenberg.

Earlier this month the National Gallery released a list of gifts of older works. More than 500 pieces have been donated in honor of the anniversary, and 320 of them will be included in an exhibition opening March 17.

Among the donors are some longtime gallery supporters, several local collectors and a number of artists and artists' families. "The Mellons have been enormously generous but they also feel it's time for others to pitch in," gallery Director J. Carter Brown said yesterday.

The Mellon gifts "were a magnet and a lodestone," Brown said. "There is a certain attractiveness, I think, to being associated with a kind of momentum, a sense of being the winning team."

The 31 Degas waxes, among them the original of the famous "Little Dancer Fourteen Years Old," come six years after the gallery received 17 other Degas waxes from Mellon, making the gallery's collection of such sculpture the most extensive in the world. "It is extraordinary to think of all these Degas waxes coming en bloc in that way," said Brown.

Among the contemporary gifts, Brown pointed to "this whole array of David Smiths," which were donated by the sculptor's family. "We really have surveyed his achievement in a medium that you normally don't think of him in, which is two-dimensional."