ADAMH, I'HYLOGEKY OF THE JAW MISCLE.S 73 



the operculum, uear its anterior edge. It pulls the operculum forward 

 and is homologous with the muscle of the same name in Amia. 



Levator operculi (L. o.). — This arises on the occipital region of the 

 skull, spreads out in a fan-like insertion on the upper, inner face of the 

 operculum. It raises the operculum. Both of these muscles are prob- 

 ably the homologues of Csd^ of ^'etter and the Cand of Ruge. 



ESOX 

 riate I IT. Figs. 1, 2 



In Esox, as in other teleosts, the dermal bones have sunk into the 

 skin so that the adductor region is free on the outside. The preoper- 

 culum, nietaptervgoid, quadrate, and post-frontal regions give the ad- 

 ductors a good surface for insertion. The teleost mandible becomes en- 

 larged and the articulation with the quadrate is greatly improved in its 

 mechanics. As the maxillaj are reduced and have lost the power to meet 

 the mandibles, their teeth have disappeared and the mandiljles are in- 

 clined inwards to meet the teeth of the palatines. 



The following description is based partly on that by Vetter (18?8) : 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (IXXERVATED BY \\) 



Adductor mandibular 4 (Add."M)f Vetter). 



Adductor mandibulcV 1 (Superficial). 



Adductor mandibula- 2 -f 3 (To symplectic, etc. Deep.). 



Levator arcus palatini (Vetter). 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 {IXXERVATED BY VI I) 



x\dductor hyomandibularis (Vetter). 

 Dilator operculi (Vetter). 

 Levator operculi (Vetter). 

 Adductor operculi (Vetter). 

 For homologies see Table I, p. lo6. 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (IXXERVATED BY F,) 



The muscles of Esox have been worked out by Vetter (1878, p. 494). 

 His names are used for the most ])art in the present description, although 

 the nomenclature of the adductor mandibuke is changed, as explained in 

 the notes. The adductor has three distinct parts. 



