PLATE II. 



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pa- me. 



pa, me. 



ps. me. 



irtc" en" 



me" 



EVOLUTION OF THE CUSPS OF THE HUMAN MOLARS. (From Osborn.) 



FIG. A. Evolution of lower molar cusps. i. Simple conical reptilian tooth. 

 2. Dromotherium. 3. Microconodon. 4. Spalacotherium. 



5. Amphitherium. 



FIG. B. Evolution of upper molar cusps. I. Anaptomorphus. 2. An upper 

 Eocene Monkey. 3. Esquimo. 4. Negro. (See addition of 

 "talon" hy, to " trigon," composed of /a, pr, me.} 



FIG. C. Lower molar cusps. I. In Miacis. 2. Anaptomorphus. 3. Homo. 

 (The cusps of the trigon and trigonid are coloured red, those of 

 the talon and talonid are coloured blue.) 



To face p. 32. 



