Kiva V is exceptional in the amount of rock-cutting that was necessary for lowering the floor to the desired level. Probably the greatest amount of stone-cutting was done in this kiva. There remains to be mentioned a unique tunnel which may eventually throw some light on ceremonial openings in the kivas of cliff-dwellings. Just beneath the adobe floor, extending from a vertical flue outside the kiva to the fire-hole, which it does not, however, enter, there is a passage through which a small person may crawl. Exteriorly this opens into a vertical flue which was broken down; inside it ends bluntly at the fire-hole. About midway of its length there extends from it a lateral passageway, slightly curved, forming a well-worn doorway. This curved passage opens through the kiva floor by a manhole. The walls of these passages are constructed of good masonry. Their function is unknown, but as most structures connected with kivas are ceremonial, this may provisionally be called a ceremonial opening. [Illustration: PLATE 27 PITCH BALLS AND VASE] It is evident that this ceremonial passage had nothing to do or at least had no connection with the ventilator and deflector of the kiva. The opening is situated under the floor, passing in its course beneath the deflector, and its external opening is by a vertical passage outside the ventilator. It also differs from the ventilator in having a lateral branch likewise situated under the floor. Passing to kivas outside the Mesa Verde region, we find homologous passages recorded as present under the floor in Pueblo Bonito, a ruin on the Chaco, and in the kiva of a ruin not far from Chama, where the passage under the floor is excavated in solid rock. Evidently we have in this structure a ceremonial opening the true significance of which is yet to be determined. Is it connected with the Tewa concept that the fire-hole is a sipapû, or was it used in fire rites that were performed about the fireplace? These and other questions that might be proposed must remain unanswered until more is known of similar passages in other cliff-dwelling kivas. A SUBTYPE OF KIVA (KIVA M) The method of roof construction, which is the main difference that distinguishes a kiva of the subtype from one of the first type, is due to the absence of pilasters. Kiva M of Cliff Palace may be assigned to this subtype, although many examples of it occur in ruins farther down the San Juan, as well as in the Navaho National Monument and in Canyon de Chelly. Kivas of the subtype are similar to those of the second type in that pilasters are absent, but they differ from them in the presence of a large banquette and in the subterranean position, which features also characterize the first type. The only circular kivas known to the ruins near the East Mesa of the Hopi of Arizona belong to the first type, two of which are found at Kukuchomo, the two ruins on the summit of the mesa above Sikyatki.