956 THE OSTEOLOGY AND MYOLOGY OF THE DEATH ADDER, 



depressor mandibulse. When the muscle reaches the costo- 

 mandibularis, its fibres spread out and are lost over this latter 

 muscle. 

 The muscle represents a portion of the sphincter colli of birds. 



Depressor mandibul^. 



M.. depressor mandihulce^ Humphry ; Neuromandihularis, Duver- 

 noy, Owen, R. Jones ; M. cervico-hyoideus (in part), Hoffmann ; 

 and N.ackenzungenheinmuskel, D'Alton. 



The depressor mandibulee arises from the aponeurosis attached 

 to the neural spines of the sixth to the twelfth vertebrae. The 

 muscle runs forward as a broad sheet over the pretrahentes 

 costarum superiores, and the deep bundles of the external 

 oblique, then bending beneath the end of the mandible it is 

 joined by the costo-mandibularis, and thereupon becomes mylohyoid. 



In Daboia and Fseudechis the muscle is intersected by two 

 tendinous bands running from the hyoid bone outwards towards 

 the end of the mandible. In these cases the muscle is quite 

 separated from the mylohyoid. 



Humphry describes in Pseudopus one band occupying the posi- 

 tion of the posterior one here, and he remarks that Reudinger sup- 

 poses it to represent an acromion. From what we have said above 

 we regard these bands as part of the cornua of the hyoid. 



The muscle is separated from the retractor oris, by a slight 

 interval, as it approaches the quadrate. This is explained on 

 referring to Hydrosaurus where we see the external auditory 

 apparatus occupying the interval. 



This muscle also corresponds to part of the sphincter colli of 

 birds. 



M. MYLO-HYOIDEUS. 



M. mylohyoideus, Hofimann; Kieferzungenheinmiishel, D'Alton ; 

 Latissiiimts ingluviei, s. platysma inyoides, Hiibner ; Hautthals- 

 muskelf Meckel ; Costo-onandibularis, Owen. 



