=Dio´genes Laer´tius.= An Epicurean philosopher, born in Cilicia. He wrote the lives of the philosophers, in ten books. This work contains an accurate account of the ancient philosophers, and is replete with anecdotes respecting them. It is compiled, however, without any plan, method, or precision, though neatness and conciseness are observable in it. =Diome´des=, a son of Tydeus and Deiphyle, was king of Ætolia, and one of the bravest of the Grecian chiefs in the Trojan war. He often engaged Hector and Æneas, and obtained much military glory. =Diome´des.= A king of Thrace, son of Mars and Cyrene, who fed his horses with human flesh. Hercules destroyed Diomedes, and gave him to his own horses to be devoured. =Di´on.= A Syracusan, son of Hipparina, famous for his power and abilities. He was related to Dionysius the First, who constantly advised with him, and at whose court he obtained great popularity. He was assassinated 354 years before the Christian era by one of his familiar friends. His death was greatly lamented by the Syracusans, who raised a monument to his memory. When Dionysius the Second ascended the throne he banished Dion, who collected some forces, and in three days made himself master of Syracuse. =Di´on Cas´sius.= A native of Nicæa in Bithynia, who was raised to some of the greatest offices of state in the Roman empire. He is celebrated as the writer of a history of Rome which occupied him twelve years in composing. =Dionys´ius= the Elder was son of Hermocrates. He signalized himself in the wars which the Syracusans carried on against Carthage, and made himself absolute at Syracuse. His tyranny rendered himself odious to his subjects. He made a subterraneous cave in a rock in the form of a human ear, which was called "the Ear of Dionysius." The sounds of this cave were all directed to one common tympanum, which had a communication with an adjoining room, where Dionysius spent part of his time in listening to what was said by those whom he had imprisoned. He died in the sixty-third year of his age, B.C. 368, after a reign of thirty-eight years. =Dionys´ius= the Younger was son of Dionysius the First and Doris. He succeeded his father, and as soon as he ascended the throne he invited Plato to his court and studied under him for some time. Plato advised him to lay aside the supreme power, in which he was supported by Dion. This highly incensed Dionysius, who banished Dion, who collected forces in Greece, and in three days rendered himself master of Syracuse, and expelled the tyrant, B.C. 357. He, however, recovered Syracuse ten years afterward, but was soon compelled to retire again by the Corinthians under Timoleon. =Dionys´ius= of Halicarnassus. A historian who left his country and came to reside in Rome that he might study all the authors who had written Roman history. He was occupied during twenty-four years on his work on Roman antiquities, which consisted of twenty books.