1 38 ELEMENT A RY ANA TO MY. [LESS. 



is generally (as notably, e.g., in the Hare and Mole) also a 

 fossa for that process of the brain called the flocculus of the 

 cerebellum. 



In some Reptiles, however (as, e.g., the Turtle), the bony 

 investment of the internal ear is incomplete on its cranial 

 side ; and in Fishes it is even widely open, forming a large 

 chamber communicating with the general cranial cavity, and 

 termed the "otocrane." 



36. That degree of completeness of THE ORBITS which 

 exists in man serving for the protection of the eyeball by 

 extensions of the cranial bones is a very exceptional condi- 

 tion. Only in him and in the higher members of his order 

 that is, the Monkeys do we find such an enclosure ; but 

 in some of them it may be more complete than it is in him, 

 by the junction of the greater wing of the sphenoid with the 

 upper maxillary bone, so that the spheno-maxillary fissure is 

 reduced to a short and rounded aperture, or even (as in the 

 Howling Monkeys) all but or quite obliterated. 



The relative size of the orbits may be much greater than in 

 man, as e.g. in Indris, in the Night- Ape (Nyctipitkecus\ or 

 in the Tarsier. On the other hand, the orbits may be rela- 

 tively smaller than in man, as in the Whales. 



Fir,. TTQ. Front Viev,* of the Skull of the Lemuroid Indris Laniger; showing 

 the large size of the orbits, which are also shown to open widely behind into 

 the temporal fossae. 



They may be much more widely separated from each 

 other in proportion to their size and the size of the skull, as 

 in the Dog and most Mammals. On the other hand, they 

 may be much more approximated, as in the Tarsier and in 

 the Squirrel Monkey (Chrysothrix\ where they are in part 

 separated by membrane only. In a great number of animals, 



