Nos. IAND2.] AX ATOMY OF SCOMBER SCOMBER. 209 



from all three divisions of the first vagus nerve, in the angle 

 formed by those divisions as they separate one from the other. 



The third interarcualis dorsalis (lad. III.) arises from the 

 antero-lateral edge of the third epibranchial, opposite the supra- 

 pharyngeal process of that bone, runs forward and slightly up- 

 ward, and is inserted on the extreme posterior end of the supra- 

 pharyngeal process of the second epibranchial. It is innervated 

 by a branch of the second vagus nerve, that arises from the ramus 

 anterior of the nervus before it separates into its two divisions. 



The fourth interarcualis dorsalis (lad. IV.) arises from the 

 antero-lateral edge of the fourth epibranchial, runs forward and 

 upward, and is inserted on the extreme posterior end of the 

 suprapharyngeal process of the third epibranchial. It is a short 

 muscle and is even more tendinous than the two preceding inter- 

 arcuals. It was innervated, in the one specimen examined, by 

 a branch that had its apparent origin from the pharyngeal portion 

 of the ramus anterior of the third vagus nerve. 



The fifth interarcualis dorsalis (lad. V.), or w^iat seems to be 

 that muscle, arises from the extreme posterior end of the fifth 

 ceratobranchial, curves upward, at first postero-laterally and then 

 antero-mesially, and is inserted on the dorsal edge of the bent, 

 articular, proximal head of the fourth epibranchial. It is, in a 

 measure, continuous with, and looks like a part of, the anterior 

 end of the constrictor of the oesophagus. Delicate branches of 

 the fourth vagus extend toward it and apparently innervate it. 



The obliquus dorsalis of the first arch (Od. I.) is simply a band 

 of degenerate tissue, tendinous rather than muscular. It arises 

 from the antero-lateral edge of the base of the suprapharyngeal 

 process of the first epibranchial, runs forward and mesially, par- 

 allel to the first suprapharyngobranchial, and is inserted on the 

 ventral part of the depression on the dorsal edge of the second 

 infrapharyngobranchial. The dorsal part of the same depression 

 gives insertion to the levator internus anterior. The obliquus 

 muscle, when viewed from below, appears as a part of the second 

 interarcualis dorsalis, a tendinous band that covers the ventral sur- 

 face of the one, continuing forward and covering the ventro- 

 posterior surface of the other: 



The obliquus dorsalis of the second arch (Od. II.) is continu- 



