70 ANNALS NEW YORK ACADEMY OF SCIENCES 



Levator arcus palatini (L. a. p.). 

 Adductor mandibulae (Ad. m.). 

 Protractor hyomandibularis (P. h.). 

 Dilator operculi (D. o.). 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 (INNERVATED BY VII) 



Adductor hyomandibularis (Ad. h.). 

 Adductor operculi (Ad. o.). 

 Levator operculi (L. o.). 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY V^) 



Levator maxillce superioris (L. m. s.). — This is derived from the mus- 

 cle of the same name in the selachians. It arises on the hyomandibular 

 and along the side of the cartilaginous part of the skull; part of it is 

 anterior to the eyes. It is attached to the adductor muscle and to the 

 dermis, between the maxilla and the palatine arch. 



Levator arcus palatini (L. a. p.). — Arises on the post-orbital process 

 and is inserted on the metapterygoid and the hyomandibular. 



Adductor mandihulce (Ad. m.). — There is a great change here from 

 the condition of the selachians. The adductor mass is now attached to 

 the bony elements of the mandible and is differentiated into three parts, 

 the second of which is again divided into two. 



(a) Pars superficialis (Ad. m.^). 



(&) Pars temporalis lateralis (Ad. m.-). 



(c) Pars temporalis medialis (Ad. m.^). 



(d) Pars intramandibularis (Ad. m.*). 



(a) Pars superficialis (Ad. m.^, A- Allis) arises from the post-orbital 

 process and the under surface and outer edge of the pterotic, and from 

 the outer face of the preoperculum, hyomandibular, quadrate, and sym- 

 plectic. It is inserted on the' coronoid and extends into the supra- 

 meckelian fossa. A tendon from this part extends to the inner side of 

 the maxilla as in the selachians. This tendon represents a muscle of the 

 selachians (levator labii superioris) that is lost in Amia, the tendon only 

 remaining. 



(&) Pars temporalis lateralis (Ad. m.-, A^). The deep portion arises 

 from the hyomandibular, quadrate, and the outer part of the metaptery- 

 goid. It joins Ad. m.^ near its insertion on the jaw. It is partly sub- 

 divided into the two parts Ad. m.^ and Ad. m.^ 



