THE MYOLOGY OF AMIURUS CATUS. 317 



tus and so exposing the under surface of the skull. It is covered 

 below by a dense fascia, in the anterior prolongation of which is the 

 bone denominated No. 4. This posterior portion arises from the 

 edges and the ascending process of the parasphenoid, and from the 

 contiguous surface of the prootic. The fibres pass directly outwards 

 and are inserted into the inner surface of the metapterygoid and an- 

 terior portion of the hyomandibular. The anterior portion may best 

 be seen on the outer surface of the skull, after removing add. mand. 

 and lev. arc. pal.. It arises from the parasphenoid, orbitosphenoid 

 and upper surface of No. 4, which is developed in the fascia covering 

 its inner surface. It passes outwards and is inserted into the inner 

 surface of the posterior half of the palatine. 



Innervation. — Both muscles are supplied by a special branch of 

 the facial — the R. muse. add. arc Us palatini. 



Action. — The posterior portion depresses or adducts the palatine 

 arch after it has been raised or abducted by the lev. arc. pal. The 

 anterior portion acts directly on the posterior extremity of the pala- 

 tine, and indirectly through it on the tentacle. By pulling the pos- 

 terior extremity of the palatine inwards it forces its anterior ex- 

 tremity outwards. To this is attached a portion of the dense fascia 

 which covers the antorbital process and adjacent parts, fibres of which 

 are also inserted into the base of the maxilla. When, therefore, the 

 muscle acts, the fascia is rendered tense, and by the arrangement of 

 the osseous parts acts on the maxilla, drawing the tentacle forwards. 

 This anterior portion acts therefore as the opponent of the add. tent. 



The muscle in Esox corresponds to the posterior portion in Amiurus, 

 the anterior portion being apparently wanting. In Gyprinus, how- 

 ever, the origin is continued forward on the orbitosphenoid, and is 

 more like what has been described. In neither of these forms, how- 

 ever, do any fibres pass to the palatine, being wholly confined to the 

 metapterygoid and entopterygoid, and extending in Perca back to 

 the hyomandibular. At first sight the anterior portion does not 

 seem to have any relation to the posterior, since, from its lying on 

 the outer (upper) surface of No. 4, it seems to belong rather to the 

 outer surface of the skull than the inner. But, when the relations 

 of that bone are considered, it is at once evident that this anterior 

 portion is a special modification of the anterior fibres of a muscle 

 similar to that of the Cyprinoids. 



