M ALPOSITION or malocclusion of units of human dentition is an important health problem. Recent surveys show that 90 per cent of all children, and, by inference, adults are afflicted with a lack of normal facial and dental arch development and its attendant maleruption, rotation, realposition, or noneruption of some teeth. This is a medical-dental problem in treatment, an oral surgical-orthodontic problem in correction, and of anthropological interest in development. We are interested primarily in a study of the factors which cause insufficient intercuspid space in the maxilla and secondarily in the mandible, although the components of the problem cannot really be separated. When there is insufficient intercuspid space, the palatal arch length is not great enough to accommodate the incisor or cuspid teeth in normal position. These teeth rotate or tip on their axis, erupt buccally, labially, or palatally (lingually in the mandible) to the median line of the arch crest or may become impacted (Figs. 1, 2, and 3). An examination of normal and abnormal growth patterns influencing arch development begins with examination of the dentofaeial complex. Accord ing to Elsasser 3 four factors are to be considered in the maxilla: (]) relation to the cranium as: a whole, (2) over-all dimensions and length of