THE MYOLOGY OF AMIURUS CATUS. 327 



(g) Arises immediately in front of the last, and is inserted into the 

 upper surface of epibr. i, near its inner extremity. 



Innervation. — (a) Is supplied by 

 (b) by a branch from tr. branchialis i. vagi; (c), (d) and (e) by branches 

 from tr. branchialis Hi. vagi ; (f) by branch from coalesced tr. 

 branchialis i. and ii., and (g) by a branch from the glossopharyngeal. 



Action. — (a) By drawing the posterior part of the pharyngeal up- 

 wards, depresses its anterior portion ; (c) and (d) act together, raising 

 the anterior border and depressing the posterior, and at the same 

 time the fibres of (d) will raise the outer border somewhat. These 

 muscles impart a rocking motion to the superior pharyngeal, which 

 must be very effective in grinding the food against the inferior 

 pharyngeal ; (6) draws the arches upwards and backwards, depressing 

 the posterior ones ; (e), (/) and (g) draw the arches directly upwards. 



Vetter describes these muscles into two groups, ' internal ' and 

 ' external.' The latter in the Cyprinoids are five in number, in 

 Esox three. They are inserted in the former into the pharyngo-brs. 

 i., ii., iii. andiv., the three posterior sending a small slip to the epibr. 

 i., ii. and iii., respectively. The fifth muscle is inserted into the pos- 

 terior portion of the superior pharyngeal, and is therefore equivalent 

 to (a). The external muscles are three, being inserted into the phary- 

 ngobrs. ii. and iii., and epibr. iv. It would be difficult to homolo- 

 gize the arrangement in Amiurus with that of the other described 

 forms, but it is to be noticed that in the former the superior phary- 

 ngeal receives three muscles but only one in the latter. 



7. Musculi Interarcuales Obliqui Dorsales. 



These are exposed by the same dissection as the preceding, which 

 must also be removed. They are three in number. The first arises 

 from near the inner extremity of the posterior edge of epibr. i., and 

 runs back above and slightly exterior to the second, to be inserted 

 into the anterior edge of the upwardly directed process of epibr. iii. 

 The second, large and stout, lies below the first. It arises from the 

 posterior border of epibr. ii., near its inner extremity, and is in- 

 serted into the extremity and anterior edge of process of epibr. 

 iii. The third arises from the inner extremity and anterior edge of 

 the pharyngobrs., between the third and fourth arches, and, pass- 

 ing back, is inserted into the extremity and anterior edge of the 

 process on epibr. iv. 



