THE SKELETON IN MAMMALIA. THE SKULL. 477 



large as the orbit, and attains its maximum development in 

 the Capybara and other Hystricomorpha ; in the Marmots, 

 Beavers, and Squirrels (Sciuromorpha), and in the Hares it is 

 undeveloped. In Lagostomus the maxilla bears an upwardly 

 directed plate of bone, shutting off from this vacuity a space 

 which is the true infra-orbital foramen. 



The zygomatic arch is always complete, and in many cases 

 the jugal extends back to form part at least of the glenoid 



1 



2- 



FIG. 98. HALF FRONT VIEW OF THE SKULL OF A PORCUPINE 

 (Hystrix cristata)x%. (Camb. Mus.) 



1. nasal. 5. premaxilla. 



2. maxillo-turbinals. 6. jugal. 



3. infra-orbital vacuity. i 1. upper incisor. 



4. maxilla. 



surface for articulation with the mandible. In Coelogenys the 

 jugal and maxillary portion of the zygomatic arch is greatly 

 expanded and roughened, and the maxillary portion encloses a 

 large cavity. The palate in Rodents is narrow, and the space 

 between the incisor and molar teeth passes imperceptibly 

 into the sides of the face. The anterior palatine foramina 

 form long, rather narrow slits in this region. The bony 

 palate between the grinding teeth is sometimes as in the Hares 



