BY W. J. McKAY. 957 



The mylohyoid, as mentioned above, is formed by the coalescing 

 of the fibres of the depressores mandibulae and costo-mandibulse. 

 The muscle may be said to arise from the ossified part of the hyoid, 

 and from the tendinous intersections when they are present. 

 Running forward the muscle meets its fellow of the opposite side 

 in the median line, while laterally it is inserted on the inferior 

 surface of the mandible, between the temporal muscle above and 

 the pterygoid below, reaching as far forward as the dentary. The 

 muscle forms a floor which hides from view the superior muscles 

 together with the nerves and vessels. 



From its origin at the hyoid bone the muscle is able to protract 

 the lingual sheath and so act on the tongue, thus resembling a 

 genio-hyoid function. 



M. INTERMANDIBULARIS. 



M. intermandihularis, Owen, Duvernoy ; Die sick kreuzen de7i 

 Muskeln des Unterkiefers^ B' Alton ; Cervico-hyoideus (in part), 

 Hofiiiiann. 



This muscle springs from the lower border of the anterior two- 

 thirds of the dentary. The fibres run inwards and backwards to 

 the mid-line, where they meet the fibres of the opposite side. At 

 their junction a well marked median raphe is formed. These 

 muscles are evidently but portions of the mylohyoid, whose fibres 

 have changed their direction with their corresponding change in 

 function, i.e., to bring the divaricated mandibles together. 

 In Hyd7'osauric8, where the muscles could be of no use in this 

 respect, the fibres of this region are specially modified to serve as 

 compressors of the sublingual glands. In Acanthophis a small 

 band is detached from the upper surface which winds round each 

 sublingual gland and performs this function. This band was first 

 pointed out by Leydig. 



From the posterior portion of the muscle a well marked band of 

 fibres runs back. It lies above the mylohyoid, and is inserted into 

 the inferior surface of the mandible. In Daboia it is connected 

 with the anterior fibrous intersection. It may represent a cerato- 

 mandibular as seen among lizards. 



