north, at Tulan (_h_); and in the Huaxtec country, at Teayo (_f_). The sign moreover bears a close analogy to that by which the Aztec expressed the period of a year (_l_), and the triangular portion of it is exactly similar to a conventional sun-ray. It is perhaps worth noting that at Copan, Uxmal and Teayo it is associated with the head of the rain-god. The significance of this symbol is obscure, but its presence over so large an area can hardly be due to coincidence. [Illustration: FIG. 86.--Details from various monuments showing the interlaced head-ornament. _a._ Copan, stela 6. _b._ Piedras Negras. _c._ Menché. _d._ Tehuacan. _e._ Xochicalco. _f._ Teayo. _g._ Uxmal. _h._ Tulan. _k._ Tenango. _l._ The Mexican year-sign. (_Zouche MS._) _m._ Island of Xico.] I think it is obvious from what has gone before, that the Aztec may be left out of account in any consideration of the source of such similarities as may be traced in Mexican and Mayan culture. They were admittedly late immigrants, from the north, into the Mexican valley, and were, at the time of their arrival, in a very low state of culture; moreover, as stated above, it is the pre-Aztec remains which show the closest relation to the Mayan. The question therefore resolves itself into an enquiry which was the earlier, the culture exemplified in the ruins of the central Maya area, or that which gave birth to the pre-Aztec remains at such early valley sites as Tulan, Teotihuacan and Azcapotzalco? Any solution of this question must also fix the relation of Oaxaca to both, and account for the Huaxtec, a Maya-speaking people whose sculptures bear no trace of a hieroglyphic script. Included in this question is that of the origin of the calendar. Let me say at once that the evidence at our disposal is not sufficient to permit these questions to be answered with certainty. Much patient excavation, both in the Mexican valley and in the central Mayan region, is necessary before the origin of the pre-Spanish civilization can be traced with any degree of finality; but I think it is possible to put forward a working theory, which must of necessity be modified in accordance with future researches, but which may at least be of service to critics as an invitation to concentrate their minds upon the subject. It is solely with this idea that I have ventured to draw up a scheme of dating (see Appendix III), and I will deal with this first, pointing out its weaknesses with as much impartiality as possible. [Illustration: _PLATE XXX_ _Photo. Guerra_ MAYA THE “HOUSE OF THE GOVERNOR,” UXMAL, YUCATAN]