Yaks are a species of daemons recognized as remnants of the primitive superstition of the Singhalese in Ceylon. They are supposed to be the authors of diseases and other misfortunes, and the Yakadura, or devil- dancer, is almost invariably called upon to overcome their malignity by his chants and charms. In these exorcisms the performers wear horrible masks, which have beaks, and are, in fact, caricatures of birds' heads. These daemons are believed to marry, and delight in dances, songs, and other amusements. They have great strength, and some of them are represented as possessing splendor and dignity.