The ossuary, now a chapel, is late Renaissance in the very elaborate Breton manner ' with Corinthian columns, lanterns, niches, and caryatids.
What was once an ossuary is now a chapel. 
mnli hypothesis: What was once an ossuary is now a chapel.  premise: The ossuary, now a chapel, is late Renaissance in the very elaborate Breton manner ' with Corinthian columns, lanterns, niches, and caryatids.