214 ALUS. [Vol. XVIII. 



The Obliqui Ventrales of the first two arches are simply a 

 few muscle fibers, or degenerate muscle tissue, filling the concave, 

 ventral surfaces of the hypobranchials of their arches, and being 

 covered externally by tendinous tissue that forms a part of the 

 muscle. This tendinous tissue arises, on each arch, from the 

 ventral surface of the distal end of the hypobranchial of the arch, 

 and is inserted on the distal end of the ceratobranchial immediately 

 beyond the cartilaginous end of that element. The tendon on the 

 first arch is always double, that on the second arch occasionally so. 



The obliquus ventralis of the third arch arises from the ventral 

 surface of the large laminar process of the third hypobranchial, 

 and from the ventral surface of the element itself lateral to that 

 process. Its fibers run laterally and slightly backward and are 

 inserted on a tendon which forms along the antero-lateral edge of 

 the muscle. This tendon runs laterally and backward, parallel to 

 the antero-lateral edge of the hypobranchial, and is inserted on 

 the antero-lateral corner of the distal end of the ceratobranchial of 

 the arch, the surface of insertion lying immediately proximal to 

 the cartilaginous tip of the element. 



The obliquus ventralis of the fourth arch arises from a tendin- 

 ous band which extends, in a curved line, from the posterior end 

 of the ventral edge of the large laminar process of the third hypo- 

 branchial of one side of the head, at first backward, then mesially 

 across the middle line of the head, and then forward to the cor- 

 responding end of the hypobranchial of the opposite side. At the 

 point where this tendon crosses the middle line of the head it is 

 attached to the cartilaginous, posterior end of the third basi- 

 branchial. The fourth obliquus arises by tendon from this tendon, 

 runs backward and slightly outward and is inserted on the anterior 

 portion of the ventral edge of the scoop-shaped distal portion 

 of the fourth ceratobranchial. The muscles of opposite sides of 

 the head, at their origins, touch each other in the middle line. 

 Although not having at all the same insertions, these muscles of 

 Scomber seem to correspond to the muscles called by Vetter, in 

 Esox, the pharyngo-arcuales. 



The first, second and third obliqui are each innervated by 

 branches of the nerves of their respective arches, undoubtedly by 

 the ramus anterior of the arch concerned, though branches from 



