516 



ZOOLOGY 



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behind. The nasal 

 cavities are very 

 large, especially 

 in the Porcupines, 

 with air sinuses 

 in the upper part. 

 In some the optic 

 foramina fuse into 

 one. An inter- 

 parietal is often 

 present. Par-oc- 

 cipital processes 

 are developed. 

 The orbit and the 

 temporal fossa are 

 always continuous. 

 The nasal bones 

 are large, and the 

 nasal apertures are 

 terminal or nearly 

 so. The pre-max- 

 illaB are always 

 very large. A re- 

 markable feature 

 of the skull is the 

 presence in many 

 of a large open- 

 ing corresponding 

 to the infra-orbital 

 foramen. The 

 middle part of the 

 zygoma is formed 

 by the jugal ; the 

 latter often helps 

 to bound the 

 glenoid cavity as 

 in the Marsupials. 

 The palate is short, 

 and the anterior 

 palatine foramina 

 large. The peri- 

 otic and tympanic 

 are ankylosed to- 

 gether, but not to 

 the neighbouring 

 bones. The coro- 

 noid process of the 



