When Wild West Sat for Its Portrait. ART: COWBOYS AND INDIANS

THE IBM Gallery of Science and Art here has assembled two handsome and entertaining exhibitions: ``American Paintings From Three New Jersey Museums.''

And ``Frontier America: Works From the Buffalo Bill Historical Center, Cody, Wyoming.''

The former consists of 65 outstanding works dating from 1730 to 1950 from the collections of the Montclair Art Museum, the New Jersey State Museum, and the Newark Museum.

The latter exhibition includes roughly 100 items, including paintings, sculptures, Indian clothing, cowboy paraphernalia, and memorabilia pertaining to the life and times of William F. (Buffalo Bill) Cody.

Both shows are special and rewarding. For general interest, however, ``Frontier America'' must take precedence, primarily because America's West has such a strong fascination for so many, and because this exhibition includes such exotic items as a huge buffalo robe, hand-tooled saddles, guns, spurs, and chaps, and several sculptures depicting the Wild West at its wildest.

Its importance, however, derives from its many excellent paintings of the western landscape, Indians and cowboys. The cowboy, in fact (both the man and the mythic figure) is central to this exhibition, although the Indian (both the human being and the legend) comes in a close second.

Artists of the time delighted in portraying the more romantic aspects of western life in large, richly detailed, and somewhat melodramatic canvases, of which Albert Bierstadt's ``Last of the Buffalo'' is an excellent example. But there were others who took a more objective view. Among them were George Catlin, whose early, smallish studies of Indian life helped establish the image of the Indian we still have today, and Karl Bodmer, whose many watercolors of the West and its inhabitants remain among the most convincing depictions of the Indian way of life ever painted.

Both artists are well represented here, and serve as an effective balance to the somewhat more sentimental or purely illustrational works by such artists as John Henry Sharp (``The Broken Bow''), Frederic Remington (``Prospecting for Cattle Range''), and Charles Russell (``When Law Dulls the Edge of Chance'').

Also not to be missed are the numerous mountain and flatland landscapes, figure and animal studies, and battle pictures by everyone from Thomas Moran to N.C. Wyeth.

There's a delicate, tiny atmospheric study of a landscape fragment by Remington that will surprise anyone not familiar with this purely painterly side of his art; a bold, extraordinary oil sketch of a buffalo head by Bierstadt that is one of the finest things in the show; a remarkable trompe l'oeil still-life by Alexander Pope; and Thomas Moran's enchanting landscape, ``Gateway To Yellowstone.''

THE IBM Gallery's second exhibition presents special problems for a reviewer. Since almost everything in it is of high quality and of special interest, it's not so easy to pinpoint a few canvases as outstanding. Any exhibition, after all, that includes fine examples by Thomas Cole, Frederic Church, George Inness, Mary Cassatt, Maurice Prendergast, John Singer Sargent, Thomas Eakins, George Bellows, John Marin, and Arthur Dove, deserves serious attention.

But even in this company, Cole's ``The Arch of Nero,'' Inness's ``Early Autumn, Montclair,'' Albert Pinkham Ryder's ``Diana's Hunt,'' Ralph Blakelock's ``Sunset,'' and Georgia O'Keeffe's ``East River From the Shelton'' stand out.

At the IBM Gallery of Science and Art, 590 Madison Avenue, through Feb. 25.