2IO 



ALUS. [Vol. XVIII. 



ous, posteriorly, with the transversus dorsalis anterior, the two 

 muscles being simply parts of a single muscle-mass. The obliquus 

 is represented by certain fibres that arise from the antero-lateral 

 edge of the dorsal surface of the proximal articular head of the 

 second epibranchial. These fibers form, on the dorsal surface of 

 the muscle-mass, a large and distinctly marked bundle, the super- 

 ficial fibers of which diverge considerably, running forward and 

 mesially. The anterior fibers of the bundle are inserted on the 

 postero-mesial face of the second infrapharyngobranchial, near its 

 dorsal edge ; the posterior fibers are inserted in a median longitu- 

 dinal sucker-like formation that forms part of the anterior trans- 

 versus. The muscle was innervated, in the first specimen 

 examined, by branches of a nerve that arose from the ganglionic 

 swelling on the second vagus, the same nerve innervating also 

 the obliquus dorsalis of the third arch and the two transversi 

 dorsales. This apparent innervation of a muscle associated with 

 the second arch by a branch of the nerve of the third arch seem- 

 ing unusual, the innervation was again carefully traced in a 

 second specimen. In this fish the branch in qliestion arose from 

 the second vagus where that nerve separated into its three prin- 

 cipal divisions, that is, at some considerable distance distal to 

 the ganglion of the nerve. Close to the root of the branch the 

 second vagus received an anastomosing branch from a nerve 

 that arose from the main truncus of the united vagus nerves, 

 proximal to the point where they separated one from the other, 

 and hence proximal to the ganglia of the several parts. The re- 

 maining part of this commissural nerve anastomosed with the 

 third and fourth vagi. The fibers of a part of that part of the 

 nerve that anastomosed with the second vagus apparently entered 

 the motor branch here under consideration, the rest of the fibers 

 going to the ramus posterior of the nervus. If this commissural 

 nerve contained motor fibers, those fibers might, accordingly, have 

 belonged in part to the first vagus, and hence would naturally 

 innervate a muscle developed in apparent connection with the 

 arch of that nerve. 



The obliquus dorsalis of the third arch (Od. III.) arises from 

 the anterior half of the dorsal surface of the proximal articular 

 head of the third epibranchial, from the mesial edge of the supra- 



