478 THE VERTEBRATE SKELETON. 



very short, sometimes as in the Capybara very long. The 

 maxilla extends back beneath the orbit to unite with the 

 squamosal. The pterygoid is always small, but sometimes 

 has a well-marked hamular process which in Hystrix, Lagos- 

 tomus, and some other genera unites with the tympanic bulla. 

 The periotic is large, and fused with the tympanic, which 

 forms a prominent bulla, and is generally drawn out into a 

 tubular meatus. The bulla attains its maximum development 

 in Chinchilla and Dipus. 



The mandible is narrow and rounded in front, the two 

 halves meeting in a long symphysis. The angle is generally 

 drawn out into a long backwardly-projecting process, which is 

 often pointed and directed upwards. In the Hares the angle 

 is rounded. The coronoid process is never large. 



There are a number of points in which the skull of the 

 Duplicidentata (Hares and Rabbits) differs from that of other 

 Rodents, (a) The sutures between the basi-occipital and 

 basisphenoid, and between the basisphenoid and presphenoid 

 remain open throughout life. (6) Much of the maxilla forming 

 the side of the face in front of the orbit is fenestrated. (c) The 

 optic foramina are united to form a single hole, much as in 

 birds, (d) The coronoid process is slightly differentiated from 

 the ascending portion of the mandible. The first two of these 

 points have been thought to indicate degradation of the 

 hares and rabbits as compared with higher mammals. 



CARNivoRA 1 . It is characteristic of the skull in Carnivora 

 that the glenoid fossa is deep, and the postglenoid process 

 (fig. 75, 23) well developed. The condyle of the mandible is 

 much elongated transversely. The orbit and temporal fossa 

 in the great majority of forms communicate freely, the post- 

 orbital bar being incomplete. 



CARNIVORA VERA. The axis of the facial portion of the 

 skull is a direct continuation of that of the cranial portion. 



1 See W. H. Flower, "On the value of the characters of the base of the 

 -cranium in the classification of the order Carnivora." P. Z. S. 1869, p. 5. 



