Which preposition to use with hagioscope

in Occurrences 2%

It has a church, built about 1250, with a gabled tower and with a hagioscope in the chancel.

on Occurrences 1%

The chancel is out of centre with the nave, necessitating a large hagioscope on N. An ungainly modern N. aisle needlessly emphasises this lop-sidedness.

Which preposition to use with  hagioscope