Fig. 18.—Lateral views, of the same length, of the upper jaws of various Primates. i, incisors; c, canines; pm, premolars; m, molars. A line is drawn through the first molar of Man, Gorilla, Cynocephalus, and Cebus, and the grinding surface of the second molar is shown in each, its anterior and internal angle being just above the m of m2.