A Skeleton believed to be that of a missing 15-year-old girl was discovered Monday in a rain-washed gully near a Duke Street construction site, Alexandria police said yesterday.

Police said the skeleton apparently was that of a girl who disappeared last summer while on the way to a city school.

"The clothing and the personal effects, plus the size of the bones, fit the description of the missing girl to a 'T'," said investigator Louis Pugh. He declined to identify the missing girl until authorities make a positive identification of the body.

Officers said they were unable to determine how the girl may have died. "There was no visible damage to the skull or any of the other bones," Pugh said.

A construction worker, Stephan D. Lee, 28, of Boston, Va., said yesterday he spotted the girl's skull about 4 p.m. Monday as he stood in the gully. "I just looked down and there it was. I didn't want to get any closer. I called police," Lee said.

The bones will be sent to the Smithsonian Institution later in the week for a detailed reconstruction, Pugh said. The head and torso were connected to each other, while arm and leg bones were scattered in the area, under a light covering of dirt and leaves, Pugh said. It was impossible to tell if the skeleton had orignially been buried, or if the dirt and leaves had accumulated naturally, he added.

The gulley is near Duke and S. West streets and the Southern Railway tracks. A new commercial building, known as Roundhouse Square, is being constructed nearby.

Pugh speculated that heavy drains during the weekend had washed away the covering over the skull, leaving it exposed when Lee walked by.