The presence of rectangular kivas in the same areas in which round kivas occur does not necessarily militate against this theory, nor does it oblige us to offer an explanation of a necessarily radical change in architecture if we would derive it from a circular form. It would indeed be very unusual to find such a change in a structure devoted to religious purposes where conservatism is so strong. The rectangular kiva is the ancient form, or rather the original form; the round kiva is not a development from it, but an introduction from an alien people. It never penetrated southward of the Colorado and upper Rio Grande drainage areas because the element which introduced it in the north was never strong enough to influence the house builders of the Gila-Salado and tributary valleys. RUINS IN TUSAYAN GENERAL FEATURES No region of our Southwest presents more instructive antiquities than the ancient province of Tusayan, more widely known as the Moki reservation. In the more limited use of the term, Tusayan is applied to the immediate surroundings of the Hopi pueblos, to which "province" it was given in the middle of the sixteenth century. In a broader sense the name would include an as yet unbounded country claimed by the component clans of this people as the homes of their ancestors. The general character and distribution of Tusayan ruins (plate XVI) has been ably presented by Mr Victor Mindeleff in a previous report.[31] While this memoir is not regarded as exhaustive, it considers most of the large ruins in immediate proximity to the three mesas on which the pueblos inhabited by the Hopi are situated. It is not my purpose here to consider all Tusayan ruins, even if I were able to do so, but to supplement with additional data the observations already published on two of the most noteworthy pueblo settlements. Broadly speaking, I have attempted archeological excavations in order to obtain more light on the nature of prehistoric life in Tusayan. It may be advantageous, however, to refer briefly to some of the ruins thus far discovered in the Tusayan region as preliminary to more systematic descriptions of the two which I have chosen for special description.