72 AWALs xinv YORK .UM/>/;i/y of SClEyCES 



muscles are inserted at a very oblique an^ie and the leverage is such as 

 to give a verv rapid movement witli comparatively slight power, 



MCSCLES OF THE ADDUCTOR OR TEMPORAL GROUl' 

 (IXXERVATED BY V^) 



Adductor mandibulffi (Ad. m.). (Divided into three parts.) 

 Protractor hyomandibularis (P. h.). 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 {IXXERVATED BY VII) 



Adductor operculi (A. o.). 

 Levator operculi ( L. o. ) . 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 {IXXERVATED BY V^) 



Ad(h((lor inandihiilcc (Ad. m.). — This muscle is divided into three 

 parts: Adductor 1 (to preoperculum), adductor 2 (along the roof of 

 the skull), adductor 3 (to quadrate). Adductor 1 takes its origin in a 

 fan-shaped mass along the outer face of the operculum. It extends 

 anteriorily, becoming tendinous at the posterior border of the eyes, and 

 is inserted in the space above the jMeckelian cartilage. Adductor 2 is 

 a long muscle arising along the entire face of the cartilaginous region of 

 the skull, from the preorbital region to the hyomandibular. It extends 

 along the roof, dorsal to the eyes and to the anterior edge of the mandi- 

 ble. The two pair almost meet in the median line, as only a thin carti- 

 laginous plate separates them. It is inserted in the Meckelian fossa 

 with the other parts of the adductor mass. Adductor 3 is a short por- 

 tion of the adductor that arises on the tiny quadrate, spreads out in a 

 thin sheet and is inserted on the coronoid process of the mandible. It 

 is a very small muscle, lying under adductor 1. 



Protractor hyomandihiilaris. — This muscle is between the dorsal and 

 the ventral parts of the adductor mandibulas. It arises on the orbito- 

 sphenoid with a small tendon at its anterior end and a fleshy attach- 

 ment to the side of the skull as it extends posteriorly to its insertion 

 on the hyomandibular. It resembles a homologous muscle found in 

 Acipenser, and Yetter calls it by the same name. 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 {IXXERVATED BY VII) 



Adductor operculi (A. o.). — This is a small muscle that arises on the 

 hvomandibular and curves arov;nd to be inserted on the inner face of 



