Passing further north, the remains of pyramids and terraces have been found at Placeres del Oro in Guerrero; these are built of natural or roughly-worked boulders, but they have not yet been excavated and it is impossible to say yet what may be their arrangement or what class of buildings they may have supported. The peculiar stone slabs found there (Fig. 16; p. 107) have been mentioned, which bear a certain resemblance to one found in the neighbourhood of Xochicalco (Fig. 33, _a_; p. 176), which itself appears to be related to those from Oaxaca (Fig. 15; p. 106). The Placeres del Oro slabs, however, are almost more like certain Peruvian work than anything else, and full excavation of this extremely interesting site is highly desirable; it is worthy of note that the latter slabs bear no glyphs. At Pazcuaro in Michoacan we hear of a three-tiered pyramid of flat stones piled together without mortar, the corners being formed of unworked blocks; but in Tarascan territory are found foundation-mounds of a specialized type, consisting of a terrace from the centre of which a spur projects at right angles, terminating in a circular platform. These are known by the name _yacata_, the term applied locally to Michoacan temples, and photographs seem to show horizontal layers of cement in their construction as in the Tlacolula buildings. On the evidence of manuscripts the temple buildings in this district seem to have been of a tower-like nature. Two varieties are shown, one on a square foundation, the other on a circular ground-plan and sometimes with a peculiar domed roof. Further north still, at La Quemada in Zacatecas, occurs an extremely interesting group of ruins, built along a lofty ridge. These remains, the most northerly yet discovered bearing a distinctly “Mexican” character, cover an extensive area and display considerable complexity. The flanks of the hills forming the ridge are built up steeply with terraced walls, and the summits are artificially levelled and broadened with terraces. The lower works seem to be of a defensive nature, and the more important buildings above consist of an intricate series of foundation-mounds, sunk courts, and occasional pyramids. From the summit radiates a system of stuccoed roads, most of which terminate in small pyramids lower down. The quadrangular arrangement of the more important structures is very noticeable, and one of the larger halls evidently possessed a roof supported on large circular pillars, built, like the walls and terraces, of unsquared stone blocks set in earth mixed with grass. The Spaniards found the ruins uninhabited, and the surrounding agricultural and hunting population of Zacatec stated that the inhabitants had migrated in the direction of Mexico after a drought lasting several years.