D.S.S. is believed to stand for "de Senatus sententia," referring to the Senate's role in providing the Ludi Apollinares - equestrian games in honor of Apollo. It was at these games that desultors, bridles and whip in hand, mounted two bare-backed horses, riding one of them and leading another, and then at full gallop leaped alternately from one horse to the other many times, changing positions with amazing agility. Young Romans, some of the highest rank, not content with driving the biga or quadriga, carried these exercises to the utmost excess. The Roman desultor wore a pileus and by managing two horses honored the memory of Pollux representing his deceased (missing) brother Castor, as well as himself.