104 THE GENERAL ANATOMY OF THE TARSII [SECT. A 



tympanic annulus is not enclosed in it. On the contrary, the 

 tympanic bone is widened to form a short funnel-shaped cylinder 

 and by this the osseous external auditory meatus is surrounded 1 . 

 (In this respect, Tarsius agrees with the true apes.) But even 

 this does not exhaust the list of peculiarities exhibited in this 

 region of the cranium of Tarsius. For the entrance to the carotid 

 canal is situated far in front of the stylo- mastoid foramen, 

 and on the ventral aspect of the auditory bulla. The latter is 

 " endotympanic " in origin (as already noted) but it seems to have 

 shared in the changes determined by the enlargement of the eyes. 

 Weber (quoted by Kampen) ascribes to that enlargement the 

 displacement of the foramen magnum towards the palate. And 

 this is supposed to have caused a corresponding displacement of 

 the auditory bulla. Such changes are therefore clearly related to 

 the specialization of the sense of sight which is so marked in 

 Tarsius. 



The basal and cranial sutural lines tend to disappear in Tarsius 

 earlier than in the Lemurs, and in this respect some resemblance 

 to the avian cranium may be perceived. Again the post-orbital 

 wall (to which the alisphenoid makes a distinct contribution) 

 constitutes a resemblance to the Anthropoidea, and severs Tarsius 

 from the Lemurs. 



Lastly the teeth must be cited as absolutely distinctive ; but 

 they serve to place Tarsius in a relatively lowly position. The 

 dental characters are so remarkable as to call for separate 

 treatment and this will be accorded to them in a later paragraph. 



Against the points thus enumerated as distinguishing Tarsius 

 from the Lemurs, another series will now be set out as a simple 

 list. These are the characters in which the two sub-orders are in 

 agreement. Thus in Tarsius and the Lemurs alike, we find that : 



1. The infraorbital canal is not roofed over in the floor of the 

 orbital cavity. 



2. At the pterion, the alisphenoid articulates with the 

 parietal bone. 



3. There is a small post-glenoid tubercle, as well as a post- 

 glenoid fossa. 



1 Cf. Kampen, Morphologisches Jahrbuch, Band xxxiv. 1905, p. 678. 



