Hierophylakes is another word for hierodidaskaloi, hieronomoi, hierophantai.
They were involved in the performing of acts of sacrifice.
The hierophantai were priests for the Eumolpidai.
Pausanias stated that new hierophantai were elected every quadrennial, and so individuals did not maintain an existence within this role for their life-time. He also stated that they might marry if they wished to do so known as, lambanein gynaika.
References
Hierophylakes Wikipedia(Text) CC BY-SA