76 ANNALS NEW YORK ACADEMY OF SCIENCES 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY V t ) 



Adductor mandibular. — This muscle completely covers the skull pos- 

 teriorly, covering the dorsal, median line to a depth of three or four milli- 

 meters. It is in two layers, a superficial (Add. 1) and a deep (Add. 3). 

 The superficial layer arises on the frontal, parietal, pterotic, and hyoman- 

 dibular, and is inserted on the coronoid region of the mandible. The 

 origin of this muscle is far different from that of the usual teleost muscle, 

 which takes origin from the preoperculum. It has spread over the skull 

 and arises much as in the reptiles. The great development of the hyo- 

 mandibular and the reduction of the opercular bones is the probable cause 

 of the change of origin. 



The deep layer (Add. 3) arises on the parasphenoid, sphenotic, hyo- 

 mandibular, and quadrate. It joins the outer layer and is inserted on the 

 mandible. 



Dilator operculi (D. o.). — This muscle is covered by the adductor. It 

 arises on the sphenotic and hyomandibular and is inserted on the upper 

 portion of the anterior border of the operculum. It raises the operculum 

 and pulls it forward. 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 (INNERVATED BY VII) 



Levator operculi (L. o.). — This arises on the posterior part of the 

 pterotic and spreads out in a fan-shaped sheet on the outside of the oper- 

 culum. It raises the operculum. This muscle is on the inside of the 

 operculum in most teleosts but in the Apodes it creeps to the outside. 

 The reduction of the opercular bones probably has something to do with 

 this change. 



PALINURICHTHYS 

 Plate III, Figs. 3, 4, 5 



The skull is fundamentally similar to that of the perch but is short 

 antero-posteriorly and with large orbits. 



The principal muscles of the jaws are as follows : 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY V 3 ) 



Adductor mandibular (1 and 2). 

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



