XIII 



PHYLUM CHORDATA 



545 



Pig. 1166.— Skull of Tiger (Fdis tigris). 

 Blainvillo.) 



(After 



In the shidl 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 

 forin 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. 



Pig. 1167.— Section of the left auditory bulla of Tiger (Fetia ^ '^^_ Cranium in 



tigria). a. aperture of communication between the two 1\iq Pinnipodia (Figf. 



chambers into which the cavity of the bulla ia divided; 1^^7o^• Tk A ' ,i 



a.m. external auditoi-y meatus; h.oc. basioccipital ; Pt. LliZ) IS DroaCl and 



periotic; ». septum between the two chambers; Sq. rniinrlofi vnfVipr fnm 



squamosal. (After Flower.) rounaeu, laiuer COm- 



