142 ANNALS NEW YORK ACADEMY OF SCIENCES 



MUSCLES INNERVATED BY THE TRIGEMINUS NERVE 



Levator maxillae superioris. 



Levator arcus palatini. 



Protractor hyomandibularis. 



Dilator operculi. 



Adductor mandibulae (often divided in the Pisces). 



MUSCLES INNERVATED BY THE FACIALIS NERVE 



Adductor hyomandibularis. Levator operculi. 



Adductor operculi. 



MUSCLES INNERVATED BY THE TRIGEMINUS NERVE 



Levator maxillae superioris (Adductor /? Yetter). 



Levator arcus palatini 1-5 McMurrich. — These are a series of muscles 

 that extend from the under side of the skull to the maxillae. They vary 

 in number in the Pisces from one to four or five. In Acanthias they arise 

 in a mass anterior to the spiracle and the remains of the first constrictor 

 dorsalis superficialis and extend to the maxillae; here they form a single 

 muscle. In Amia they are partly anterior to the eyes. They probably 

 represent the dorsal part of the first constrictor superficialis and function 

 in the movement of the maxillae. In the teleosts they lose their impor- 

 tance and disappear, except for a few tendinous remains, while the levator 

 arcus palatini becomes more important and usurps the place of the lev- 

 ators of the maxillae. 



Levator arcus palatini. — This muscle raises the bones of the palatine 

 region and is of great importance in the fishes where this region is de- 

 veloped. In the elasmobranchs it is not needed, but is perhaps repre- 

 sented by the remains of the first constrictor, just anterior to the spiracle. 

 It is prominent in most teleosts and Holostei, but drops out where this 

 region becomes fixed. This muscle is closely related to the protractor 

 hyomandibularis and the dilator operculi. McMurrich (1885) calls the 

 protractor hyomandibularis "levator arcus palatini" in Amia. They are 

 often close together and sometimes not entirely separated as in Amia. 



Protractor hyomandibularis. — This draws the hyomandibular forward. 

 It probably represents a part of the first constrictor. It is always closely 

 connected with the levator arcus palatini. It varies in size, being very 

 large in Acipenser and Polyodon, of good size in the teleosts, and absent 

 in the dipnoans, where the hyomandibular is rudimentary or absent. 



Dilator operculi. — This is the posterior slip of the first constrictor. It 

 pulls the operculum forward and slightly raises it. It is closely con- 



