Site where endolymph is seen:
(b) Scala media(Ref. Scott Brown, 8th ed., Vol 2, page 545)Endolymph is present in the membranous labyrinth, whereas perilymph is present in the bony labyrinth.Hence scala vestibuli, scala tympani and their interconnection helicotrema, which are parts of bony labyrinth, are filled with perilymph.Scala media, utricle, saccule and semicircular canals, which are parts of membranous labyrinth, are filled with endolymph.
Scala vestibuli
Scala media
Helicotrema
Scala tympani
Ear