CEOS, an island in the Aegean sea (Gr. KEws mod. ZEA or TzIA), 14 m. off the coast of Attica, in the group of the Cyclades and the eparchy of Syra. Its greatest length is about 15 m. and its breadth about 8 m. Mount Elias in the centre is 1,864 ft. high. Among its productions are lemons, citrons, olives, wine, honey and valonia. There were formerly four towns in the island :—Iulis, about 3 m. from the north-west shore, represented by the town of Zea, Coressia, the harbour of Iulis, Carthaea, in the south-east, at S'tais Polais village ; and Poieessa, in the south-west. Iulis was the birthplace of the lyric poets Simonides and Bacchylides, the philosophers Prodicus and Ariston, and the physician Erasistra tus. From its excellent code, the title of Cean Laws passed into a proverb. One of them forbade a citizen to protract his life beyond sixty years. Ceos fought on the Greek side at Artemisium and Salamis; joined the Delian League, and also the Athenian alliance in 377 B.C. ; revolted in 363-362, but was reduced again. Athens then assumed monopoly of the ruddle, or red earth, the most val uable product of the island. Ceos was divided in A.D. 1207 among four Italian adventurers ; was included in the duchy of Naxos in 1537; passed under Turkish rule in 1566 and thence into the Greek kingdom. Silver coins of Carthaea and Coressia date from the 6th century B.C. (see NUMISMATICS : Greek, "Cyclades and Sporades"). See Pridik, De Cei Insulae rebus (1892).