A liturgical book written in the 6th, 7th, or 8th century, probably in the Frankish kingdom.
The book exists in several manuscripts, the oldest of which is preserved in the Vatican Library (manuscript Reginae 316).
In none of the old manuscripts does the book bear the name Gelasius but is simply called "Liber Sacramentorum Romanre ecclesire."
However, an old tradition, based on Walafrid Strabo; ascribes what is evidently this book to Pope Gelasius I.
The book comprises three parts, made up of Masses for Sundays and feasts, prayers, rites and blessings of the Easter font and of the oil, dedication .of churches, and reception of nuns.
New Catholic Dictionary