One of the ancient Greek modes. This mode was renamed lydian by medieval theorists who misunderstood the Greek treatises.
Boethius, in his description of ancient Greek usage, stated that the hypolydian mode was a musical scale which would be represented in modern form as the octave-species from F to F, in ascending order thus ("t" = whole-tone, "s" = semitone):
F G A B C D E F t t t s t t s
Note that this example illustrates the diatonic genus -- the various ancient Greek modes had variant interval structures, depending on the genus and shade.