Phylox series

The  was, according to the TARDIS data bank, a series of planets in either the Andromeda constellation or galaxy. Nyssa explained to the Fifth Doctor that Castrovalva was "in Andromeda. A small planet of the Phylox series." (TV: Castrovalva)

The "series" may have been the "Phylox system" of the Andromeda galaxy that the Wirrn devastated. (PROSE: Placebo Effect)