James H. Raby, 78, a lawyer who had practiced in Alexandria since 1941 and who helped win a case that desegregated bus travel in Virginia, died of a pulmonary embolism Thursday at Howard University Hospital.

Mr. Raby, who was born in Norfolk, graduated from Armstrong High School in Washington. He worked for the Government Printing Office, the Post Office and elsewhere while earning his law degree at Howard. He established his practice in Alexandria and was the founder of the firm of Raby & Stafford there.

Among his cases was that of Lottie E. Taylor, who brought a suit to desegregate buses in Virginia. A decision in her favor was handed down by the Virginia Supreme Court. He was a member of the D.C. and Virginia bar associations.

Mr. Raby, who maintained residences in Alexandria and Washington, was a member of the Campbell AME Church in Washington, a chairman of its board of trustees, an assistant superintendent and teacher in its Sunday School and a member of its Men's Club.

He also was president of the Lay League of the Second Episcopal District of the AME Church and national legal counsel to the Lay Organization of the World. He was an Elk and a legal adviser to the Virginia state organization of Elks. He was a Prince Hall Mason and a member of the Pigskin Club.

His wife, Georgie F. Raby, died in 1966.

Survivors include three daughters, Frances R. Richardson of Hampton, Va., Mildred L. Raby of Washington, and Mary Stafford of Arlington; a twin brother, Walter John Raby of Philadelphia, and five grandchildren.