stucco reliefs. In Yucatan the roof-comb, where found, differs from those of the central Maya area in consisting, not of two inclined walls, but of a single vertical wall (Fig. 74, _l_), and it is often replaced by an elaborate false front, (Fig. 74, _j_), rising above the vertical entablature, the ornament of which it carries up to a greater height. But though the roof-comb may by its weight have assisted in giving stability to the Maya building, it was by no means essential, the thick walls and solid roof were constructed of stones freely mixed with mortar, and the result was a structure which was practically a monolith; in fact, the Maya built caves, the exterior surfaces of which they faced with a veneer of dressed slabs, often, especially in Yucatan, carved and arranged to form elaborate mosaic decoration. Their method of building was extremely wasteful of space, and Holmes says of the so-called “Governor’s Palace” at Uxmal, figured on Pl. XXX; p. 358, “We find by a rough computation that the structure occupies some 325,000 cubic feet of space, upwards of 200,000 of which is solid masonry, while only about 110,000 feet is chamber-space. If the substructure be taken into account, the mass of masonry is to the chamber-space approximately as 40 to 1.” In the case of the buildings at Tikal, the proportion of chamber-space is considerably less (see Fig. 76, 11). In some cases at any rate the connection of the superimposed building with the foundation-mound on which it rested is emphasized by the fact that the walls of the former continue downwards into the heart of the latter (according to Holmes), possibly even to the ground-level. The doorways by which these buildings were entered are for the most part simple. In the more massive structures, such as Tikal and Copan, a single doorway seems to have been the rule; but at the sites which display greater architectural advancement, such as Palenque, the front is often broken by a series of doorways so close together that the wall becomes little more than a series of square pillars (Fig. 75, _d_). Round columns are found only in Yucatan, especially at Chichen Itza, associated with those buildings which are attributed to a later date (Pl. XXIX). It is interesting to note that, while in the Old World the column is based for the most part on vegetal forms, in this country the animal world has been laid under contribution. The Chichen columns are carved to represent feathered serpents, with their heads upon the ground and their tails elevated in the air, exactly similar to the columns which have been found at Tulan in Mexico. Stone was employed for lintels, especially at Menché, where they are elaborately carved, but wood was used almost more frequently. The carved lintels of Tikal (see Fig. 48; p. 225), of the durable zapote wood, are among the finest examples of Maya art, and have survived owing to the solidity of the buildings and their single doorways. At Palenque and in Yucatan the wooden lintels,