82 ANNALS NEW YORK ACADEMY OF SCIENCES 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY V 3 ) 



Adductor mandibular (Ad. m.). 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 [INNERVATED BY VII) 



Levator operculi (L. o.). 



MUSCLES OF THE ADDUCTOR OR TEMPORAL GROUP 

 (INNERVATED BY V 3 ) 



Adductor mandibulce. — The adductor muscles of Neoceratodus are the 

 largest found in fishes. The adductor is divided into two slips — a mas- 

 seter (Adm 1 ) and a temporal (Adm 2 ) — which give the cutting and 

 crushing power to the powerful dental plates. 



(a) The masseter slip (Adm. 1 ) is quite small and much shorter than 

 the. temporal portion of the adductor. It arises in the quadrate region 

 and extends forward to be inserted behind and below the insertion of the 

 rest of the adductor. It also has a small tendinous sheet, but it is small 

 in comparison with the sheet of the main adductor. 



(&) The temporal slip (Adm 2 ) is the larger of the two muscles. It 

 arises along the cartilaginous brain case, extending from a point anterior 

 to the eyes to the posterior part of the brain capsule and extending well 

 down on the sides. It is also attached to the bones of the roof of the 

 skull, where they cover it. In dissection the muscle is seen to be broken 

 up into small bundles that are attached to the side walls of the skull. In 

 the median line the cartilaginous skull does not extend to the roof of the 

 skull in the region of the adductor muscles, so that the muscles fill this 

 gap. They nearly meet in the midline, being separated only by some 

 tendons of the long neck muscles and by fascia. This part of the ad- 

 ductor is divided by a great tendinous sheet to which the fibers from both 

 sides join. It is very heavy and thick, thus giving great power. It is 

 inserted on the coronoid region in the Meckelian cartilage region. 



MUSCLES OF THE DEPRESSOR OR DIGASTRIC GROUP 

 (INNERVATED BY VII) 



Levator operculi. — The levator is the only other muscle in the upper 

 part of the skull. It arises on the posterior face of the lower part of the 

 cartilaginous capsule and is inserted on the inner side of the opercular 

 region. 



The mandibles are depressed by the long ventral muscles that are at- 

 tached to the mandibles close to the symphysis and by the hyoid muscles. 



