A JADE NOTCHED DISC, YABI Late Neolithic period - early Shang dynastyA JADE NOTCHED DISC, YABILate Neolithic period - early Shang dynastyA wide aperture at the center, notched on the outer edge three evenly spaced wedges swirling toward the same direction, each wedge with three shallow square tabs on the ridge and a indent at the tip, the inner rim slightly larger on one side and finished with a shallow groove, the flat sides with lines of cutting tracks polished smooth, the stone evenly 'calcified' to cream color with few earth encrustations still remain. 5 7/8in (15cm) diam新石器時期末-商早期 玉牙壁Qing dynasty connoisseur Wu Dacheng (1835-1902) identified in his publication Guyu tukao the notched jade disc as Xuanji (璿璣) (vol. 2, p. 50a), a mythic, poetic name first recorded in Shang shu (Book of Documents) as xuanji yuheng (璿璣玉衡), a reference interpreted by Han dynasty scholars as an astrological device used in ancient rituals. However, in 20th century archaeological excavations the notched jade discs were often placed together with circular jade discs (bi) on the chest of the deceased in the burial context, therefore the term yabi (toothed disc) was assigned to correctly address function.A smaller jade yabi, with pairs of blunt notched teeth carved on each of the three arcs, excavated from a Longshan Culture (circa 3000-1700 B.C.) site at Tengxian, Shandong province, is illustrated by Xia, Kaogu xuebao, 1984, No. 4, pl. 2:1, with a stone example from a late Shang burial at Anyang, Henan province, loc. cit., pl. 1. The same jade yabi is illustrated in color in Zhongguo yuqi quanji (Compendium of Chinese Jades), Vol. 1, Primitive Society, Shijiazhuang, 1992, p. 34, col. pl. 42.Another similar jade yabi in the collection of the Palace Museum, Beijing is illustrated in Gugong bowuyuan cang wenwu zhenpin quanji (The Complete Collection of Treasures of the Palace Museum), Jadeware (I), Hong Kong, 1995, p. 58, no. 49; and another similar yabi in the collection of the Kaifeng Museum is illustrated by Gu (ed.), Zhongguo chuanshi yuqi quanji (Chinese Jades in Traditional Collections), Vol. 1, Neolithic Period, Shang, Western Zhou, Spring and Autumn Period, Warring States Period, Beijing, 2010, p. 84.Compare also the yabi of similar form in the Arthur M. Sackler Gallery, Washington D.C., illustrated in Asian Art in the Arthur M. Sackler Gallery, The Inaugural Gift, Washington, D.C., 1987, p. 89, no. 45; another illustrated by Loehr, Ancient Chinese Jades from the Grenville L. Winthrop Collection in the Fogg Art Museum, Harvard University, Cambridge, 1975, p. 103, no. 106; and another closely related jade yabi in the British Museum, illustrated by Rawson, Chinese Jade from the Neolithic to the Qing, London, 1995, p. 163, pl. 8:1.For a comprehensive discussion of yabi discs excavated in China, see Luan, "Yabi yanjiu (Researches on Yabi)," Wenwu, 2005, No. 7, pp. 69-81.