The remarkable glaze seen on this bowl was an innovation of the pioneering potters at the Jizhou kilns in Jiangxi province. Known as 'tortoise shell' glaze, its name was derived supposedly from its similarity to the shell of a warm-water sea turtle known as the hawksbill. Compare two similar 'tortoise shell'-glazed conical bowls, the first from the Charles B. Hoyt Collection, and now in the Museum of Fine Arts, Boston, illustrated in Oriental Ceramics, The World's Great Collections, vol. 10, Tokyo, 1980, no. 172; the second illustrated in Song Ceramics from the Kwan Collection, Hong Kong, 1994, no. 170.