1. In growing sheep fed on a low-calcium diet for 12 months and for a similar period on a diet of adequate mineral content, a tendency for the incisor teeth to protrude beyond the maxillary pad (prognathism) was observed. This arose primarily during the repair period, and was apparently caused by poorer repair of the upper skull than of the mandible. This was not observed in animals fed on a control diet or one deficient in phosphorus and vitamin D.
2. A malocclusion of molar teeth associated with poorly mineralized and extremely weak mandibles, which prevented the incisor teeth from meeting the dental pad, occurred in growing sheep fed for 12 months on a diet deficient in phosphorus and vitamin D. This defect was not observed in similar animals fed on a control diet nor in those fed on a diet of low calcium content. Treatment effects on the shape of the mandible that were apparently related to this malocclusion are described.