For many visitors to the Pentagon, one of the most solemn moments on tours there comes when they are ushered into a purple-colored alcove where - according to guides - the names of "every one" of the more than 3,391 recipients of the Medal of Honor, the nation's highest military award, are enshrined.

Most visitors gaze in awe at the small silver-colored nameplates that line the walls of the alcove, called the Hall of Heros. Not Richard N. Sheldon of Arlington.

A listorian for the National Archives. Sheldon's eyes quickly scanned the names of Spanish-American war medal winners and, to his amazement, discovered missing the name of the one of the war's "biggest heros." Absent was the name of Navy Lt. Richmond P. Hobson, an Alabama native who gained widespread publicity during the war for the brief "suicide mission" he led in Cuba in an effort to sink a collier to block the Santiago harbor.

Pentagon spokesman confirmed that Hobson, who served eight years in the House of Representatives from Alabama after the war, was somehow overlooked when Defense Department officials asembled names for the alcoves.

Sheldon, 43, who wrote his Ph. D. dissertation on Hobson's role as a champion of women's rights and prohibition, said he discovered the man's name missing when he recently toured the Pentagon for the first time.

Although Pentagon spokesmen did not have an explanation for the oversight, Sheldon says he suspects Hobson was overlooked because he did not receive his medal until 1933, when Congress passed a special act granting him the reward. At the time of the Spanish American war the medals were granted only to enlisted servicemen and Hobson, as an officer, was ineligible for the medal.

Pentagon officials said they will soon and Hobson's name to the alcove, which is 9 years old.