Scree at the Foot of Mount Matthiessen : ON THE RIVER STYX AND OTHER STORIES <i> by Peter Matthiessen (Random House: $17.95; 208 pp.; 0-394-55399-3) </i>

Since 1950, Peter Matthiessen has been sending in award-winning books like “The Snow Leopard,” “Far Tortuga,” “At Play in the Fields of the Lord,” “Blue Meridian.” Picture him sunburned and lean in a snapshot blur, wearing a flap-pocketed khaki shirt with epaulets, maybe a brimmed canvas hat--in the rain forests of Brazil; Bolivia; Nepal; Mexico. Now in these trivial days when the last tufts of paradise have been tramped flat, the suburban book reviewer of a younger generation resorts to dressing him up for readers who will find him on the racks of the South Coast Plaza Banana Republic. But the irony is that Matthiessen has always been an authentic pilgrim, in the original sense of the word, the soles of his feet burning on account of a restlessness that one might call, with due embarrassment, “religious.”

Some writers prefer to stay home and sink into a single place, a single New England town, to saturate it with consciousness, while others “go out” and “bring back” the trophy of their story. Matthiessen is mostly of the latter type, though in fact what he brings back from his expeditions is, at its best, ourselves--our neighbors--our own faith and errors. With each new book, he ranges over an unthought-of new territory, but entirely unprotected by a tourist’s superficiality. It’s like he never got his inoculations.

This new volume encloses the 10 short stories Matthiessen has published during his career. It’s not surprising (the present short-story revival being so recent, perhaps even temporary) that a writer of Matthiessen’s stature should have produced only 10 stories in 40 years. And indeed, this miscellaneous collection does feel like raked-together scree at the foot of a mountain. In a generous and candid impulse of autobiography, Matthiessen has arranged them in chronological order, beginning with some he wrote before he got out of college. And in a brief preface, he has, like a good host, put us at ease by giving us permission to be critical (“. . . of course one hopes that in close to 40 years there has been a little bit of progress”). Yet the remarkable thing is how good almost all of them are, the undergraduate ones as well as last year’s.

The stories describe this pilgrim’s progress. The early ones, averaging just 10 pages in length, are best represented by the first, a bright flare of early genius, about the domestication of dogs and the cruelty of our “domestication” of each other. The three final stories, averaging triple the length of the early ones, are more technically accomplished; we no longer have to forgive the undergraduate’s occasional wonky metaphor, or the sense that, thematically, the story’s surface is disturbed by a hidden shoal that the author himself doesn’t see.

Three samples. The last story is about a CIA operative who returns from Zaire, where apparently he’s been involved with the assassination of Patrice Lumumba; he tries to recover his sense of belonging in the American neighborhood by going duck hunting on the Hudson River, only to have a difficult run-in with some poor African Americans fishing on the bank. The second-to-last story is about a couple of Yankee tourists in the Florida swamp whose intrusion in a small town upsets the delicate balance of racism and corruption. And the third-to-last is about a volunteer worker in a mental hospital who makes the mistake of falling in love with a patient, causing (according to the quirky but implacable justice of nightmares) a conflagration in the wards.

Even in the civilized United States, Matthiessen’s characters are in the jungle, and occasionally his stories accomplish that miracle which is fiction’s job: making us look at what we’re doing. When the haze of familiarity departs, we see common objects glisten in their real uses--a fork, a Walkman, a bottle of bourbon--and before averting our eyes we glimpse how tribal, how carnivorous, how mammalian is our conduct.

There are of course a few pieces here that Matthiessen must regret, especially in thebook’s first half. But an artist’s “mistakes” are as valuable as his or her “successes.” In a sense, more valuable. For a “mistake” is not a dead-end but a doorway leading to the necessary self-transcendence. An example here is “Horse Latitudes,” a deformed story about the joshing hostility between a pious Christian missionary and a Lebanese merchant, which in 1959 emerged into the world unfinished and unfixable. Perhaps it affords a certain Punch-and-Judy comedy, but its characters’ motives are murky, their conflicts unresolved and ill-defined. Yet this story clearly was the first pang of the magnificent novel, “At Play in the Fields of the Lord.”

This story and others, among the early efforts, are peopled by imperfect mutations who are to become the great characters of his later work. Thus the collection is valuable as an addition to the moral universe that Matthiessen has been creating over the years: He is without fail a naturalist and an anthropologist, nostalgic for wildness, and for the integrity of the Native, whether in the American suburbs or in the rising mists of the Amazon jungle.