In the sccond part of my doctorate dissertation entitled “A Mctric Approach to thc Study of the Evolution of Human Denti- tion” presented to Harvard University in 1939, I had studied thc rela- tive size of the permanent incisors in the great anthropoids and hom- inids by means of diagrams.^ In the published summary of this thesis, in this regard, I had stated: “/n the common ancestors of Hominidae and Pongidae the size of the incisors relative to the size of the molars was small as in man and gorillay^ During the course of a second visit to the United States in 1946 and 1947, I had occasion, by utilizing the col- lections of the American Muscum of Natural History in New York and thc United States National Museum in Washington, D. C., especially that of thc latter institution, to enlarge the series of some species of infra-human primates which I had studied at Harvard, and also to add the measuremeE-'j M 0 UPLLILU htıd ııut ■ examincd bcforc. In view of this body of material and the new fossil discoveries that have accrued since 1939, I have considered it worth- while to study the rclative size of incisors in the suborder Anthro- poidea,^ by the extcnsion of an index that had been utilized by the late Prof. Wcidenreich.