124 



ALUS. [Vol. XVIII. 



ever, that must, in that case, be the suprapharyngobranchial ele- 

 ment Hes ventral to instead of dorsal to the efferent artery of the 

 arch. Its relation to the dorsal end of the afferent artery was not 

 determined, and as that artery, at its dorsal end, lies somewhat 

 ventral to the efferent artery it may lie ventral also to the supra- 

 pharyngobranchial. If this be so, which I consider doubtful, van 

 Wijhe's expression "Kiemenvene" would refer to this artery and 

 not to the efferent one as I was led to conclude in my work on 

 Amia (No. 4, p. 662). If, as seems probable, both arteries lie dor- 

 sal to the element, van Wijhe's definition cannot apply to this 

 piece in Scomber. It will, however, be treated as a suprapharyn- 

 gobranchial. 



In the second and third arches all the normal elements are 

 found excepting only the suprapharyngobranchials, which are 

 wanting. In the fourth arch both the suprapharyngobranchial and 

 hypobranchial are wanting, unless the latter element is represented 

 in that small median piece of cartilage with which the cerato- 

 branchial of the arch articulates, in which case the little cartilage 

 represents, as already stated, the fused hypobranchials of opposite 

 sides of the head. The fifth arch contains only a ceratobranchial 

 and a<small detached piece similar to the one, which, in Amia (No. 

 4, p. 649), I considered as the epibranchial rather than the supra- 

 pharyngobranchial of the arch. The third and fourth infra- 

 pharyngobranchials are firmly united to form a single piece. 



The gill opening between the fourth and fifth arches lies, as in 

 Amia, entirely on the ventral aspect of the arches, and does not ex- 

 tend to their outer or posterior angles. 



The Three Hypobranchials decrease regularly in length 

 from the first to the third arch. 



The First Hypobranchial {HB, I) may be said to consist 

 of a shank ; a large, flat, somewhat triangular portion, on which is 

 found the articular edge of the piece ; and a pointed anterior end, 

 or process. The shank of the bone is semicylindrical, occupies 

 somewhat more than the posterior half of the element, and is 

 deeply grooved on its ventral surface. The ventral edge of the 

 triangular articular portion is formed by the anterior part of the 

 true ventral surface of the element, is grooved, though less deeply 

 so than the shank posterior to it, and is separated from the 



