were evidently made in moulds. Excavations have shown that the valley type of pottery occurs only in the surface layers, and is therefore comparatively recent and represents a period of short duration; beneath it, and extending to a considerable depth, are found fragments of a ware which is especially associated with the ruined city of Teotihuacan. The most characteristic form belonging to this period is a circular bowl with vertical, or almost vertical, sides supported on three feet, either flat or of the cascabel type (Fig. 38). These vases are usually coated with a burnished red, yellow, Fig. 38.—Pottery vase from Teotihuacan. brown or black slip, and are either plain or are ornamented with bold incised curvilinear patterns, or human and animal masks moulded in relief. Impressed designs were also applied by means of stamps. Flat shallow bowls of this ware are also found, and graceful vases with everted lip, but the finest specimens are covered with polychrome ornament of a peculiar technique. The design is engraved in the outer slip, and the background cut away, leaving the former standing out against the matt colour of the paste; in some cases the intaglio portions have received a coating of cinnabar or vermilion, and in the most beautiful examples the excised portions have been filled with slip of various colours, rendering the finished vase a kind of polychrome champ-levé in clay, a vivid blue-green being the most prominent colour. Vases are also found with a design produced by the alternation of matt and burnished surfaces. A peculiar feature of Teotihuacan is constituted by the innumerable small pottery heads