ILLUSTRATIONS 



B. Restoration of same. 



C. Skull of Zalambdalcstes lechei. Natural size. 



D. Restoration of same. 



(AH after Gregory and Simpson.) 



30. — The Pen-tailed Tree-shrew of Borneo facing 52 



A "living fossil" representing a little-modifled sur- 

 vivor of the Cretaceous ancestors of the Primates. 



(Based on photographs and data given by Le Gros 

 Clark.) 



31. — The Spectral Tarsier of Borneo facing 53 



A highly specialized modern survivor of a diversified 

 group of primates that lived in the Lower Eocene epoch 

 over fifty million years ago. (Drawn from specimen 

 preserved in formalin, with aid of data from photo- 

 graph of a living Tarsius by H. C. Raven.) 



32. — Skeleton of a Primitive Fossil Primate 

 (Notharctus osborni), from the Eocene of 

 Wyoming ...... facing 54 



33. — Skull of a Primitive Primate of the 



Eocene Epoch {Notharctus osborni) . . 55 



Natural size. (After Gregory.) 



34. — Ascending Grades of Faces in the Lower 



Primates ...... facing 56 



A. Lemur (Lemur variegatus) with fox-like muzzle 

 and laterally-placed eyes. (After Elliot.) 



B. South American Monkey {Cebus capucinus) 

 with shortened muzzle and widely separated nostrils. 

 (After Elliot.) 



C. Old World Monkey (Lasiopyga pygerythrus) with 

 nostrils approximated and forwardly-directed eyes. 

 (After Elliot.) 



35. — Top View of the Skull in Representatives 

 of Six Families of Primates, Showing the 

 More Forward Direction of the Orbits 

 IN the Higher Forms .... 58 

 xviii 



