Text: It boasts a fine south porch and marble and alabaster treasures that evoke the wealth of the diocese in the 16th and 17th centuries, particularly the elaborate chapel screens and, in the northern arm of the transept, an intricate 16th-century astronomical clock.
Entailment: There are treasures made of marble and alabaster.
Contradiction: There isn't a south porch and the "treasures" were made primarily from straw.