Of architectural remains as a whole it may be said that the Aztec buildings show a tendency to simplicity and exhibit on the whole fewer traces of arrangement on a large and comprehensive plan, such as may be observed at Teotihuacan. Teotihuacan itself, as far as actual buildings are concerned, has many points in common with Tulan, and in its general arrangement shows a considerable similarity to Monte Alban. The last-named site is obviously closely connected with other remains in Oaxaca; and Xochicalco, from its decoration, has similar affinities, affinities which extend to the pre-Aztec remains of the valley. Mitla stands practically by itself as far as artistic ornamentation is concerned, though the arrangement of the buildings is quite Oaxacan in character. The Totonac ruins display a certain affinity with the ruins at Quiengola, though this affinity cannot be said to be direct. The true relation between the two will be more apparent after the Maya remains have been considered. It is unsafe to draw any conclusion from structural points alone, since so much depended upon the presence in the neighbourhood of suitable materials; it was, for instance, the presence of trachyte in the Mitla region which enabled its builders to make use of large masses of stone, and provided the long lintels which distinguish this group of ruins. Where suitable stone was lacking, the deficiency was usually supplied by cement, and much use was made of the latter to correct irregularities in construction, though its employment appears to have been more frequent in Oaxaca and the Totonac region than elsewhere. [Illustration: FIG. 36.--Mexican pottery forms (see also Pls. XVII-XIX). 1–3. Valley of Mexico. 4. Oaxaca. 5–9. Island of Sacrificios. (_British Museum_)] [Illustration: FIG. 37.--Designs from Mexican pottery; late valley type.]