xxiii. 4 



PRIMATE SKULLS 



611 



Tarsi us 



Lemur 



Notharctus 



Fig. 387. Skulls of early primates. (After Gregory and Flower and Lydekker, 

 Mammals, Living and Extinct, A. & C. Black, Ltd.) 



Fig. 388. Tympanic ring and tympanic bulla. 



A, Primitive mammalian condition, floor of cavity unossified. B, Lcmuriformes, ring 



enclosed within bulla. C, Lorisiformes and platyrrhines, ring part of bulla. D, Tarsius and 



catarrhines, bony meatus. (After Le Gros Clark, Early Forerunners of Man.) 



within a petrosal bulla, but not fused with it (Fig. 388), a condition 

 like that in Tupaia, but not found in higher primates. The pollex and 

 hallux are used for grasping; most of the digits have nails, but the 

 second digit of the foot has a toilet claw. The fourth digit is usually the 

 longest, whereas in anthropoids the whole symmetry of the hand and 

 foot is arranged about a long third digit. The teeth show the typical 



2.1.'}.'? 

 primate number , but the upper incisors are very small and the 



2.1.3.3 

 lower incisors and canines are procumbent, that is to say directed 



forwards and are used for combing the fur. The first lower premolar 



