Complex sentence: The rib vaulting is divided into two bays as on the ground floor but here the six corbels and the ceiling bosses are decorated with finely carved busts or foliage.
Split into simpler sentences: The rib vaulting is again divided into two bays and is similar to that on the ground floor. But on the first floor the six corbels and the ceiling bosses are decorated with finely carved busts or foliage.