THE MYOLOGY OF AMIURUS CATUS. Ally 
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. are. 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. 
Inmervation.—Both muscles are supplied by a special branch of 
the facial—the #. musc. add. arcis 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 #sox corresponds to the posterior portion in Amiurus, 
the anterior portion being apparently wanting. In Cyprinus, how- 
ever, the origin is continued forward on the orbitosphenoid, and is 
more hike 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. 
