Summus an Etruscan and Roman divinity, the god of the nightly sky, the lightning- darter of the night, as Jupiter was of the day. His temple stood near the Circus Maximus, and a representation of him in clay was given in the pediment of the Capitoline temple. Whenever a tree was struck by lightning in the night, the Arvail brothers would offer a black ram to Summaniu (Pliny, II. N. 2, 53; August. De Civ. Dei, 4:23 Varro, De Ling. Lat. 5, 74; Livy, 32:29,; Ovid, Fast. 6:731; Cicero, De Div. 1, 10, etc.).