868 



PHYLUM CHORDATA : CLASS MAMMALIA 



There are generally strong occipital and sagittal crests for 

 the insertion of muscles of neck and jaw. The glenoid 

 fossa for the articulation of the lower jaw is deeply concave, 

 and bounded by a large postglenoid process, the result 

 being that the lower jaw can only move up and down. 

 This is important, as it minimises the risk of any failure 

 of grip in seizing living prey. The muscles of the lower 



Fig. 515.- Skull of tiger, lateral view. 



px., Premaxilla ; mx., maxilla. Note the insertion of upper canine 

 (c.i) just behind the suture line, and the fact that the lower canine 

 (c.2) bites in front of it. na., Nasals ; la., lachrymal bone with 

 foramen ; fr., frontal ; pa., parietal ; so., supra-occipital ; 

 pa., paroccipital process ; au., auditory aperture (the reference 

 line crosses the inflated bulla) ; sq., zygomatic process of squa- 

 mosal ; a., angle of lower jaw ; jii., jugal ; ca., camassial tooth 

 of upper jaw ; co., coronoid process of lower jaw. 



jaw are very strongly developed, and with this may be 

 associated the strength and the protrusion of the zygomatic 

 arch in the more specialised types. The widening of this 

 arch has prevented the formation of a frontal bridge behind 

 the orbit, so that the orbit is confluent with the temporal 

 fossa. There is a strongly developed and ossified tentorium 

 descending between cerebrum and cerebellum. The tym- 

 panic bullae are in most cases large. 



The clavicles are incomplete or absent (an important 



