Under the Virgin and Child are five small arches with figures. These are, from the left, a crowned female saint holding a cross, Saint Paul, Saint Dominic, a male saint, and a kneeling nun. This last figure, presented in a different scale, is the donor of the painting. This is one of the earliest surviving examples of a small, independent panel containing a predella. The original engaged frame shows that the painting is a complete devotional image, not part of a larger ensemble.
Source: Laurence Kanter, "Virgin and Child," in Eye of the Beholder, edited by Alan Chong et al. (Boston: ISGM and Beacon Press, 2003): 43