74 ANNALS NEW YORK ACADEMY OF SCIENCES 



Adductor mandibulce Jf. (Add. w of Vetter, 1878, p. 494). — This large 

 muscle mass fills the suprameckelian fossa and is attached to the side of 

 the fossa and to the cartilage. It is homologous with that found in Amia 

 (Ad. m. 4 ) and in several other forms where the Meckelian fossa is large. 



Adductor mandibulce 1 (Vetter, 1878, p. 494). — This is the outer sheet 

 of the adductor, which completely covers the rest of the muscle. It 

 takes its origin from the edge of the f rontals, from the postorbitals to 

 the articulation of the hyomandibular, along the face of the hyoman- 

 dibular and the anterior face of the preoperculum ; the lower part arises 

 from the symplectic and the postero-ventral portion of the quadrate. 

 It ends at the mandible with a short, wide tendon and joins with the 

 rest of the adductor mass, to be inserted in the mandible, in the coro- 

 noid region and in the suprameckelian fossa. 



Adductor mandibulce 2. — This is underneath the superficial adductor 

 (Add. m. 1 ). It arises on the metapterygoid, preoperculum, quadrate, and 

 has a slight origin on the hyomandibular and operculum. This com- 

 plex muscle becomes tendinous at the anterior end and extends to the 

 jaw medial to the superficial adductor. It extends into the supra- 

 meckelian fossa to join the rest of the adductor. 



Adductor mandibulce 3. — The deepest portion of the adductor mass. 

 Its tendon joins that of Ad. m. 2 . 



Levator arcus palatini (L. a. p.) (Vetter). — This is found along the 

 upper part of the post-frontal region, after the adductor mandibular 1 

 is removed. It arises on the pterotic and alisphenoid and is inserted 

 on the metapterygoid and hyomandibular. It pulls up on the palatine 

 region and closes the gills. 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 {INNERVATED BY VII) 



Adductor hyomandibularis (Ad. hy.) (Vetter, 1878, p. 502). — A small 

 muscle between the hyomandibular and the skull that arises on the skull 

 wall in the otic region and is inserted on the inner side of the hyoman- 

 dibular. It adducts the hyomandibular, as its name indicates. 



Dilator operculi (D. o.). — This muscle is not to be seen until the 

 adductor mandibular 1 is lifted off. It extends from the pterotic to the 

 operculum. It arises on the pterotic and hyomandibular and extends 

 over the hyomandibular and under the tip of the preoperculum to be 

 inserted on the upper, inner face of the operculum. It opens the opercu- 

 lar cavity. 



Levator operculi (L. o.). — This muscle is just posterior to the dilator 

 operculi. It arises on the posterior end of the pterotic with a slight 



