IT'S HARD to keep a local culture distinct as everything is shoveled into the global melting pot. In that regard, the Urhobo are relatively fortunate.

The Niger Delta tribe was barely more than a rumor to the first European explorers of West Africa and wasn't properly ascertained until the late 19th century. Even today, the 1.5 million Urhobo are overshadowed by such larger Nigerian groups as the Yoruba.

That leaves the Urhobo something of a mystery. The title of a current exhibition at the National Museum of African Art, "Where Gods and Mortals Meet: Continuity and Renewal in Urhobo Art," suggests that everything will be explained. In fact, the show offers an equal measure of fascinating objects -- among them ancestor columns, maternity figures and embodiments of male aggression -- and unanswered questions. It's an introduction, not a summation.

"Where Gods and Mortals Meet" was organized for New York's Museum for African Art by Perkins Foss, who seems to have had Urhobo scholarship largely to himself. Foss first traveled to Nigeria in 1965 and has been studying the Urhobo ever since. A mix of art, history and anthropology, the show supplements objects and text with videos of dances and ceremonies made between 1972 and 2001. They are all the work of Foss.

Most of the exhibition's other contributors go unnamed, as their exquisitely detailed masks, statues and other ritual objects are unsigned. This work is not "art" in the contemporary Western sense, which involves self-expression, formal innovation and, quite often, audacious marketing.

The wooden sculptures were made for ceremonial purposes to honor elders, ancestors, brides and mothers, nature spirits and others in the eternal cycle of life. "Continuity" here is no ethnological platitude; it's the essence of traditional agrarian society.

The most remarkable objects -- artistically and culturally -- are the iphri, shrines to aggression. Like the ancestor columns, these carved wooden objects often combine several faces in one entity but with the focus on a large, central mouth. Rows of teeth, sometimes supplemented by saberlike fangs, emphasize the fierceness of these totems, which are said to crave food. Once, every man who fought or hunted would have an iphri to focus his belligerence, and large ones would be carried into war.

Now, when renewing the powers of an iphri, the Urhobo will make offerings of food and drink and stage a mock battle in which the military commander carries the shrine.

Despite such uses, iphri don't only threaten violence. They're also emblems of sublimated pugnacity, representing Urhobo men's reputation for being good public speakers. Today, they're commonly kept by males who have difficulty restraining their temper. Although their fanged countenances suggest the sheer evil of horror-movie fiends, the statues actually symbolize psychological balance.

The details are specific to the Urhobo, but a lot of this is typical of traditional, nature-oriented societies; strength, fertility and family elders have been venerated throughout the world. Urhobo customs resemble those of, for example, East Asia, where ancestor worship is also common. The larger-than-life figures of edjo, looming statues of a community's founders, are kept in darkened shrines that are closed for all but a few days a year. This is not unlike the custom of Japanese temples and shrines, which often cloister sacred objects that are revealed only on special occasions.

The exhibition's final section concerns water-spirit rituals and consists mostly of masks, with some photos and videos and a half-size reconstruction of the "big animal," a woven costume from a 1972 festival. The Urhobo live among several rivers and believe that powerful spirits live in them. They also use the image of a canoe -- shown here in a carved form that may have been carried in dances -- to represent the journey to the next world.

Exactly where these objects and rites fit in the history of the Urhobo, or their current existence, is unclear. The wooden works in the show, worn and faded and thus possessing a ragged beauty that has nothing to do with their original appearance, are undated. Only one can be placed chronologically: an unweathered mask whose carving is shown in a 1972 Foss video. It's impossible to say if its more battered counterparts are 50 years older or 500 -- although the former seems more likely.

Also on display are some copper objects, mostly bells, that were not made by the Urhobo. (One, in fact, was cast in England.) Discovered by accident by farmers and fishermen in the region, the bells are considered gifts from the spirit world. They're now part of Urhobo culture yet tell us nothing about it.

Aside from Foss, one other name recurs here, contrasting the anonymity of the traditional art. It's that of Bruce Onobrakpeya, an adroit Urhobo printmaker whose work combines Western technique with Nigerian motifs (not just those of his tribe). His etchings, scattered throughout the galleries, feature strong forms and vivid colors, and depict items and observances that correspond to the masks and statues. Yet one man's art doesn't seem enough to constitute the "renewal" promised by the show's title.

In fact, it's impossible to gauge the health of Urhobo traditions from this exhibition. Some comments in the catalogue suggest that they're in decline, but that's far from obvious. Someday, the tribe may be perfectly analyzed and catalogued. But such creations as the toothy, ravenous iphri have a power that can never be fully explained away.

WHERE GODS AND MORTALS MEET: CONTINUITY AND RENEWAL IN URHOBO ART -- Through Sept. 25 at the National Museum of African Art, 950 Independence Ave. SW. 202-633-4600. Open daily 9 to 5:30.

An iphri, a statue for male aggression, in "Where Gods and Mortals Meet."Carefully detailed Urhobo masks were made for ceremonies. Edjo statues honor community founders. "Currency," made of copper alloy by the Urhobo people of Nigeria.Urhobo printmaker Bruce Onobrakpeya's "Udju Mara (Family Going to Farm)," part of the Urhobo art exhibit at the National Museum of African Art.