Complex sentence: San Lorenzo, on the contrary, became a titular for a chancellor ia of the order of priests, and a deaconry for a cardinal-deacon; when he is a sub-urbicarian bishop, the chancellor retains this church in commendam.
Split into simpler sentences: San Lorenzo, on the contrary, is a titular when the chancellor ia of the order of priests, and a deaconry when he is a cardinal-deacon. When, on the other hand, he is a sub-urbicarian bishop, the chancellor retains this church in commendam.