Ultragammon

Synopsis from the patent:
"A backgammon board game for two, three or four players wherein the movement spaces are positioned in the form of a cross. Each of the players is given 15 stones which they must move around the board according to rules which are similar to those used in conventional backgammon. The stones of each player are of a color different from the stones of the other players."

The rules include 6 new games that can be played on the 4-player backgammon board: Warm Up, Stacked, Ultracross, Heavy Traffic (4 dice per player), Itche and Ultra-Wars.