The reference is to the discussion at MP I:84 of St Jerome with St Christopher and St. Louis of Toulouse (or St. Augustine if the inscription 'de Civitate Dei' on the back of his book is accepted as genuine) in the Church of San Giovanni Crisostomo in Venice, a late work, signed and dated MDXIII / IOANNES BELLINUS. P. It is again described at Works, 4.319 and at Works, 11.387 it is said to be among the most perfect in the world.