Robert Hunter, the primary lyricist on many of the Grateful Dead’s most memorable songs, including “Uncle John’s Band,” “Scarlet Begonias,” “Dark Star” and “Truckin’,” died on Monday night at his home in San Rafael, Calif. He was 78.

His family announced his death in a statement. His agent, Steve Martin, said Mr. Hunter had recently had surgery.

Mr. Hunter’s lyrics, often dreamlike variations on the American folk tradition, meshed seamlessly with the band’s casual musical style, helping to define the Grateful Dead as a counterculture touchstone. Interpreting his slippery lyrics became a favorite pastime of the band's most fervent fans, the Deadheads, something he relished.