The existence in Mexico at the time of the Conquest, of a dual state, suggests the possibility that, in some way, the pyramids of Teotihuacan continued to be connected with the opposite and rival cults of the Sun and the Nocturnal Heaven, although their origin was shrouded in the past. It is known that their site was venerated: besides, the name Teotihuacan, which Orozco y Berra translated as “the place of the masters as keepers of the gods” or “the place where the gods were adored,” most probably really meant “the divine four-sided mountains or pyramids” or, possibly, “the sacred pyramids of the lords.” Until an extensive, carefully-planned and systematical exploration has been carried out at Teotihuacan, it is impossible to form any definite conclusions concerning its past history. Cherishing the hope that such an exploration may yet be made during my lifetime, I shall merely make a few remarks concerning the ruins, which I visited many years ago. Approaching them from the south one enters a broad straight road, several miles in length and about 250 feet wide, which is bordered at each side by a series of irregular mounds, probably covering ruined structures. This imposing road leads directly into the vast courtyard which stretches across the base of the great pyramid of the Moon. As the City of Mexico lies to the south of Teotihuacan it is significant to find that this road leads from that direction to a vast pyramid situated at the north, which was, according to the ancient Mexicans, the region of the Underworld, darkness and death. It is not surprising, therefore, to find that the ancient native name which still clings to the roadway is “the path of the dead.” The presence, moreover, of innumerable small clay heads which are, undoubtedly, portraits or effigies of persons represented as dead, points to the alternative that Teotihuacan may have been the necropolis of an ancient civilization or that it was, even at the time of the Conquest, the place where a register of deaths was kept by the priest-rulers, by means of small clay effigies. Considering the native idea, it seems more than probable that all matters pertaining to the dead should be relegated to the northern region and the fact that the road from the south leads to a pyramid which tradition associates with the moon, the symbol of the nocturnal cult of the “Below,” lends color to these views.