934 THE OSTEOLOGY AND MYOLOGY OF THE DEATH ADDER, 



It is interesting to find this muscle in the ophidians from its 

 relation to the columella in the lacertilians, since we see the bone 

 disappearing, but the muscle remaining to aid as an elevator of the 

 mandible. 



M. PTERYGOIDEUS EXTERNDS. 



Part of posterior temporal, Hoffmann, D' Alton, Owen, Jones, 

 Duvernoy. 



On the posterior temporal muscle being removed, the fibres of 

 the external pterygoid are displayed, arising from the whole of the 

 anterior edge and part of the internal surface of the quadrate ; the 

 muscle runs downwards to be inserted into the whole of the man- 

 dibular fossa. The muscle is separated from the posterior temporal 

 by fascia, and by the inferior dental nerve which winds round its 

 anterior edge to gain the external surface, where it runs to enter 

 the foramen on the mandibular fossa. The muscles presented no 

 differences in any of the snakes examined. The muscle is usually 

 regarded as part of the posterior temporal, and no previous observer 

 has described it as being at all separated from the posterior tem- 

 poral. Whatever be the proper homologue of this muscle it must 

 certainly be described as being quite distinct from the posterior 

 temporal. We think it approaches more closely to the external 

 pterygoid than the muscle usually described under that name. It 

 is supplied by the third division of the fifth nerve. 



M. PTERYGOIDEUS INTERNUS. 



M. tranverso-7naxiUo-pterygo7na7idihiIaris, Hoffmann ; Aeussere 

 Flugelmuskel, D'Alton ; Pterygoideus exteo^nus, von Teutleben ; 

 Pterijgoicleus externns et internus, Duvernoy and R. Jones ; M. 

 ehtopteryg Oldens et M. entopterygoideiis, Owen. 



The internal pterygoid arises by two heads. The external or 

 inferior head springs from the lower portion of the external 

 surface of the posterior two-thirds of the mandible. The inner head 

 arises from the lower part of the posterior third of the inner face 

 of the mandible, and from the capsule of the quadrato-mandibular 

 ioint, and from the inferior extremity of the quadrate bone. The 



