You start with the Lord Jesus, and then you have Adam and Noah. Thereafter the dispensation heads.
Then you step down, appreciably, and come to prophets and apostles, to the elders of Israel, and to wise and good and sagacious men who have the spirit of light and understanding. Every prophet is a witness of Christ; every dispensation head is a revealer of Christ for his day; and every other prophet or apostle who comes is a reflection and an echo and an exponent of the dispensation head.
All such come to echo to the world and to expound and unfold what God has revealed through the man who was appointed for that era to give his eternal word to the world. Such is the dispensation concept.
(Bruce R. McConkie, Doctrinal Commentary on the Book of Mormon Vol. 2, p. 220)