THE MYOLOGY OF AIMURUS CATUS. 323 



dorsal surface of the muscle. Opposite the second branchial arch a 

 slip (HBr 1 ) separates from the main muscle and is inserted into the 

 inner extremity of the anterior ridge of ceratobranchial iii. A 

 second slip (HBr 2 ) is inserted similarly into ceratobranchial iv., the 

 main muscle passing straight backwards to be inserted into the an- 

 terior border of the pharyngeal inferior (ceratobranchial v.) In a 

 specimen of Amiurus nigricans (Les) Gill, fibres were also seen pass- 

 ing from the main muscle to ceratobranchials i. and ii. Certain 

 interarcual slips run parallel to the muscle proper, and, from their 

 relation to the slips to the ceratobranchials, may be considered as sec- 

 ondary parts of it. One (HBr 3 ) arises from the point of attachment 

 of the slip to ceratobranchial iii., and passes back to the anterior 

 ridge of ceratobranchial iv., its insertion being closely related with 

 that of slip from main muscle to the same bone. A second bundle 

 (HBr 4 ) continues this first one backwards, and is inserted into the 

 inferior pharyngeal (ceratobranchial) along with the main muscle. 



Action.— The hyoid being fixed it will draw the branchial appara- 

 tus forward, the interarcual slips approximating the arches to which 

 they are attached. 



As indicated by the synonyms, the muscle under consideration i& 

 probably comparable to two or more distinct muscles in other Teleo- 

 stei. Tne main muscle seems to have certain analogies with the 

 muscle in Perca, termed by Vetter the pharyngo-hyoideus, and by 

 Owen the branchi-depressor, which extends from the urohyal to the 

 inferior pharyngeals on either side. The pharyngo-arcualis, which 

 is present in Esox and the Cyprinoids (in which the pharyngo- 

 hyoideus is absent), but absent in Perca, also presents resemblances. 

 It arises from the anterior border of the inferior pharyngeal, and 

 divides into two slips, the outer of which passes to ceratobranchial 

 iv., and is, therefore, comparable to the interarcual slip extending 

 between the same parts in A miurus. The inner portion inserts into 

 hypobranchial iii., uniting in Esox with the obliqui ventrales of 

 ceratobranchial iv. and hypobranchial iii. The first of these latter 

 muscles in Esox and the Cyprinoids sends a slip to the ceratohyal, 

 and that of the fourth arch besides passing to its own ceratobranchial 

 sends also a slip to the hypobranchial iii. 



I am inclined to consider the hyobranchialis of Amiurus as equi- 

 valent to all these parts. If one imagines the pharyngo-hyoideus of 

 Perca, and the pharyngo-arcualis of Esox and the Cyprinoids united, 



