The silly feature of the O.Henry's--the awarding of first and second prizes--continues to be silly, this year quite noticeably so since the first prize goes to a hackneyed piece of southern-family-loyalty business by Ernest J. Finney called "Peacocks"; while the second-place finisher--Joyce Carol Oates' "House Hunting," a genuine agoraphobic nightmare--is so much the stronger. John Casey's "Avid"--a portrait of a rich young woman adrift--is the most narratively rich of the stories here; Charles Dickinson's vivid "Child in the Leaves" offers strong reward as well. Two overtly "plain" stories also score: Frances Sherwood's unadorned rÇsumÇ of a mixed marriage, "History": and Charles Simmons' artfully underplayed high-school-ethics drama, "Clandestine Acts." James Salter's "American Express" is involving but almost too suave, becoming an exercise in high-sheen mannerism; David Foster Wallace's fitful "Here and There" is editor Abrahams' concession to nonrealistic fiction. The rest is fairly alkaline: stories by Alice Adams, T. Coraghessan Boyle, Millicent Dillon, and others.