xxiii. 6 



TARS1ERS 



615 



pattern and the incisors and canines do not show the specializations 

 found in lemurs (Fig. 383). The head is more like that of a monkey 

 than of a lemur; it is set on a mobile neck, indeed the animal has the 

 uncanny power of turning its head through 180 so that it faces back- 

 wards, while the eyes, like those of owls, are so large that they are 

 little movable. The foramen magnum opens downwards. The eyes 

 face more nearly forwards than in lemurs, the snout is shortened, and 

 the turbinals of the nose reduced. The nose thus resembles that of a 



mt.(cut) 



Lemur mt I LL 



Fig. 394. The nasal passages of various mammals. 

 cp. choanal passage; mt. maxillo-turbinal; nt. naso-turbinal; I-IV, endo-turbinals. 

 (From Cave, B.M.A. Ann. Proc. 1948.) 



monkey (Fig. 394), and there is neither a cleft in the upper lip nor a 

 moist rhinarium, such as is present in most mammals and in lemurs, 

 but absent in anthropoids. This reduction of the snout as a tactile 

 organ perhaps goes with the development of the hand for that purpose. 

 The eyes are enormous, relatively larger than in any other Primate, 

 but suited for night vision, with the retina containing only rods, 

 though, nevertheless, possessing a yellow macula and a small fovea. 

 The external ears are large and mobile and the sense of hearing is keen. 

 The orbit is partly divided off from the temporal fossa (Fig. 387). The 

 tympanic bone is not only fused to the very large petrosal bulla but 

 also somewhat drawn out into a spout, as in anthropoids (Fig. 388). 

 The brain is small and shows a curious mixture of early mammalian 

 and advanced primate characters. The olfactory regions are small and 

 the cerebral hemispheres large, though smooth. The visual (occipital) 



