XIII 



PHYLUM CHORDATA 



545 



FIG. 



1166. Skull of Tiger (Felis tigris). 

 Blainville.) 



(After 



In the skull of the Carnivora vera (Figs. 1166 and 1168) there 



are prominent sagittal and lambdoidal crests. The temporal 



fossae are very deep; the 



orbits are not separated 



from them by bone. The 



relative development of the 



facial region varies in the 



different groups ; in the 



Bears and their allies, and 



in the Dogs, it is elongated ; 



in the Cats it is very short. 



The zygoma is strong and 



greatly arched outwards. 



The glenoid cavity is in the 



form of a transverse groove, 



to the shape of which the 



transversely elongated con- 



dyle is adapted. In the Cats 



there is a large, rounded 



tympanic bulla (Fig. 1167), 



the cavity of which is 



divided into two parts an- 

 terior and posterior by a 



septum, the anterior con- 

 taining the auditory ossicles and the opening of the Eustachian 



tube; the bony auditory meatus is short: the paroccipital is closely 



applied to the posterior surface of the tympanic bulla. In the 



Dogs the septum of 

 the bulla is incom- 

 plete, the auditory 

 meatus short, and 

 the paroccipital pro- 

 cess not applied to 

 the bulla. In the 

 Bears and their allies 

 (Fig. 1169), the bulla 

 is usually less dilated, 

 and the septum is 

 absent or only re- 

 presented by a ridge, 

 while the bony audi- 

 tory meatus is elon- 

 _ gated. 



FIG. 1167. -Section of the left auditory bulla of Tiger (Felis "^ ^^l 11111 . * n 



titjris). a. aperture of communication between the two the Pinnipedia \ Iff. 



chambers into which the cavity of the bulla is divided; -, t hy-\ TL J ' J 



a.m. external auditory rneatus ; b.oc. basioccipital ; PL 1172) IS broad and 



periotic; a. septum between the two chambers; Sq. rnn nf{*t\ rathpr rnm- 



squamosal. (After Flower.) lOUnGCd, latner COm 



