150 THE SKULL. [chap. 



bulla divided into two cavities by a bony partition, in having 

 the paroccipital spread over the hinder surface of the bulla, 

 and in having no prolonged external auditory meatus ; but 

 the bulla is more elongated and compressed, and the inner 

 chamber is placed altogether behind the outer or true 

 tympanic chamber. 



In the Hyaena this region of the skull much resembles the 

 same part in the Cats, but the bulla is simple and undivided. 

 In the Dogs there is a partial septum, and otherwise the 

 characters are intermediate between the two extremes of the 

 Bears on one side, and the Cats on the other. 1 



In nearly all the Carnivora the hyoidean apparatus is con- 

 structed on the same plan as described in the Dog, having a 

 narrow, transversely elongated, curved basihyal, either round, 

 or compressed from above downwards, a nearly straight 

 compressed thyrohyal, not ankylosed with the basihyal, and 

 a well-ossified anterior cornu, composed of three distinct 

 pieces of subequal length. In the Lion, Tiger, and Leopard, 

 however, the anterior arch is imperfectly ossified, the dif- 

 ferent bones being small, and connected together by long 

 ligamentous intervals ; but in the Puma, Cheetah, Lynx, and 

 Cat, the bones are large, and in close relation with each 

 other. 



In the Seals the brain-cavity is very broad, round, and 

 rather depressed. The orbits are large, and the interorbital 

 portion of the skull greatly compressed. The olfactory 

 chambers of the nasal cavities are consequently very narrow, 

 and the ethmoturbinals little developed ; but in front of the 

 orbits the cavities widen, and the maxilloturbinals are very 



1 For the various modifications of the structure of this part of the 

 skull in the different genera of the order, see "On the Value of the 

 Characters of the Base of the Cranium in the Classification of the Order 

 Carnivora." (Proc. Zool. Soc, 1869, p. 5.) 



