The first gallery of primitive cave art to be found in North America has been discovered 1,100 feet down in a Tennessee cave at the end of several low, watery passages, researchers said yesterday.

Thousands of drawings of people, birds, turtles, and a variety of other animals are etched into the soft mud walls of a 300-foot-long underground passage that served 800 years ago as a sanctuary for drawing and possible rituals.

The newly discovered gallery doubles the entire quantity of art ever found from the Mississippian culture, a civilization that inhabited America's Mississippi River basin from 900 to 1700 A.D., according to Jon Muller, a prehistoric American art expert from Southern Illinois University in Carbondale, Ill., who was part of the team studying the drawings.

"A decorated cave like this is unique in North America so far, and it may be unique in the world," said Charles Faulkner, anthropologist at the University of Tennessee.

Faulkner is the leader of the group, which yesterday presented pictures and explanations of the discovery.

Although some Indian art is chiseled in rock shelters elsewhere in North America, the researchers said that the gallery of drawings is unique because it is etched in mud in a deep cave, and because the find so far exceeds other art of the period in both quantity and its nearly perfect preservation.

Like the famous and much older deep cave art of Lascaux, France, this gallery apparently was used by the artists for no purposes other than as a sanctuary where drawings were made and where some rituals connected with them may have been carried out, Muller said at a news conference at the National Geographic Society.

The society sponsored the expedition to examine and photograph the cave.

Patty Jo Watson of Washington University in St. Louis, an expert in American cave research, said this cave is unlike anything else she has seen or heard of.

She said prehistoric people were avid cave explorers, and evidence of their presence has been found in many caves.

But in all other cases, she said, the people either were living in the caves, exploring them, or digging for minerals only.

"The closest parallel is with the ice age art in caves in the south of France," she said, where several hundred cave paintings were made in shrines about 15,000 years ago.

Half a dozen samples of ash, taken from cane torches used by the Indians to light the gallery as they made the drawings, showed dates ranging from 460 to 1730 A.D. But the researchers said that most of the drawings probably were made between 1100 and 1300 A.D., because most of the carbon dates cluster in that period and many of the images match those from other art objects of that time.

The walls of the cave were covered with mud of the consistency of modeling clay.

The drawings were scratched into this clay with fingers or sticks. Because the environment of the cave has been uniform for thousands of years, with an even temperature and 100 percent humidity, the soft mud and its etchings have not deteriorated.

The size and complexity of the drawings varies. Some are a few inches high, and others are yards long. Some appear to be childish stick figures, and others are far more elaborate tracings with multiple outlines.

Some areas are gouged out and others are raised to make three-dimensional features. There are some footprints pressed into the soft walls.

Images are scratched on top of images, and in some cases it appears that some of the animal images were struck with sticks or logs as a sort of ritual killing, Muller said.

As in the cave paintings of France, he said, it appears the act of making the drawings was the important thing, and preserving them quite unimportant.

Muller said it appears that there were few people, perhaps fewer than half a dozen, who drew the images and possibly used the cave for religious purposes.

Although the cave may have been first entered with torches about 460 A.D. for exploration, it is believed that the artists frequented it about 1150 A.D.

The cave, now called "Mud Glyph Cave" by the researchers, was familiar to people in the East Tenessee area where it is located, but it did not appear to be more than about 75 feet deep.

Beyond the first cavern, however, a small hole led to others and at the end of a 30-foot stretch so low that it could only be traversed on the stomach, a long gallery was recently discovered, 10 feet high, 15 feet wide, and 315 feet long.

The gallery was first found by Walter Merrell, a spelunker, or cave explorer, and U.S. Forest Service ranger.

Those exploring the cave are determined to keep its location secret, because the mud drawings could easily be damaged and because plunderers who heard of the underground gallery have already entered the cave once to dig for valuable artifacts.