Easton's Bible Dictionary (1897)
The “Dioscuri”, two heroes of Greek and Roman mythology. Their figures were probably painted or sculptured on the prow of the ship which Luke refers to (Acts 28:11). They were regarded as the tutelary divinities of sailors. They appeared in the heavens as the constellation Gemini.
Smith's Bible Dictionary (1863)
(Acts 28:11) the twin sons of Jupiter and Leda, were regarded as the tutelary divinities of sailors; hence their image was often used as a figure-head for ships. They appeared in heaven as the constellation Gemini . In art they were sometimes represented simply as stars hovering over a ship.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
CASTOR AND POLLUX. Acts 28:11. In heathen mythology "Castor" and "Pollux" were the names of twin sons of Jupiter who presided over the Castor and Pollux. ) destinies of sailors. Hence an image representing them was often seen on the prow of ancient ships, like the figureheads of modern days. In the case of Paul's ship, the name was Castor and Pollux.