On the Anatomy and Phylogenetic Position of Polypterus. 391 



Adductor mandibulac is tiivided into 3 portions: 

 Masseter, 

 Tenaporal, 

 Pterygoid. 



Masseter. Beneath the preoperculum (cheek bone) lies the very 

 powerful masseter (figs. 2 and 3). It may be considered as consisting 

 of two parts, an upper and a lower. The upper and larger portion 

 takes its origin from the upper and posterior edges of the preoper- 

 culum. It then runs forwards and slightly downwards to the coronoid 

 process of the lower jaw. This portion is innervated by a separate 

 branch from the mandibular nerve. 



The lower portion of the masseter arises from the ossified antero- 

 external surface of the quadrate and proceeds parallel with the other 

 portion to the base of the coronoid process. Its nerve supply is a 

 branch arising from the mandibular nerve much lower down than the 

 preceding branch. 



The Temporalis (figs. 2 and 3) arises from the sphenotic, post- 

 Irontal, supraorbital cartilage band and frontal. The attachment to 

 the last named is to its under surface between its projecting edge and 

 its articulation with the orbitosphenoid extending even above the eye. 

 Along this same surface stretches the supraorbital cartilage band. 

 The temporalis takes a direct course downwards to the lower jaw. 



The Pterygoid (figs. 3, 30) arises at the base of the skull some- 

 what behind the level of origin of the Temporalis from the parasphe- 

 noid posteriorly and the orbitosphenoid anteriorly. It runs to the 

 lower jaw at an angle of about 45 degrees to the horizontal plane of 

 the skull and is inserted, forming a common tendon with the Tempo- 

 ralis on to the ossified Meckel'.s cartilage. The above three muscles 

 are very stout and the bite of Folypterus must be very powerful 

 while the gape is not great. The orbitosphenoids architecturally sup- 

 poi-t the frontals so that they may not be depressed by the stress of 

 the Temporalis. The temporal and pterygoid muscles are innervated by 

 a branch, arising near its exit from the mandibular nerve. 



Outside the last two muscles run the buccal and superior maxillaris 

 nerves as well as finer nerves to the mucous canals of the postorbital 

 and postarticular regions. 



Ventral, longitudinal muscles belonging to the trunk. 

 Coracoarcuales. 

 The Coracohyoideus (fig. 5) is a very stout muscle showing slight 



