936 THE OSTEOLOGY AND MYOLOGY OF THE DEATH ADDER, 



downwards and backwards to be inserted into the whole of the 

 triangular area on the upper surface of the articular, immediately 

 behind the quadrato-mandibular articulation. The two bellies are 

 more distinct in Morelia. They also appear to be well marked in 

 Crotalus diirissus as figured by Duvernoy. 



The muscle is supplied by the seventh nerve. 



Its lower portion is covered externally by the fibres of the 

 retractor oris. It is the chief muscle in opening the mouth of the 

 snake, since it acts on the posterior extremity of the mandible, 

 raising it and so depressing the anterior portion. 



M. PTERYGO-SPHENOiDALis (Levator palati). 



M. pterygo-sphenoidalis 2^osterior, Hofi'mann; Innere hintere 

 Flitgelmicskel, D' Alton; Spheno-pterygoid, Duvernoy, R. Jones: 

 Fresplieno-pterygoideus^ Owen. 



The pterygo-sphenoidalis arises from the lateral surface of the 

 parasphenoid bone as a narrow strip of muscle ; this runs back- 

 wards and is continuous with a broader belly which arises from 

 a special excavation on the basisphenoid, close to the median line. 

 The muscle runs downwards, backwards, and outwards to be 

 inserted on the superior surface of the posterior half of the ptery- 

 goid bone. At its origin the muscle has the spheno-vomerine 

 muscle lying externally, while the parieto pterygoid lies externally 

 at its insertion. The muscle is hidden from view by the aponeurosis 

 that covers the roof of the mouth. 



According to Owen it represents the levator tympani of fishes. 

 We, however, regard it as the levator palati for the reasons given 

 below. 



The muscle is one of the most powerful of the head group, and 

 is the chief protractor of the pterygoid bone, and hence the chief 

 erector of the fang. 



M. PTERYGO-PARiETALis. (Part of teiisor palati). 



M. pterygo-parietalisj Hofimann ; Der Hehemiiskel des inneren 

 Fliigelbeins, D'Alton ; M. orbitalis, Hiibner ; M. j^ost-orhito- 

 palatine, R. Jones; not mentioned by Owen. 



