FISHERY BULLETIN: VOL. 82, NO. 4 



a 



FIGURE 35. — Left interopercles in lateral view. a. Scomberomorus semi fasciatus , New Guinea, 510 mm FL. b. Scomber- 

 omorus sinensis, Hong Kong, 677 mm FL. c. Acanthocybium solandri, Revillagigedos Is., 1,068 mm FL. d. Grammator- 

 cynus bilineatus, Marshall Is., 424 mm FL. 



the Sardini (Collette and Chao 1975), Thunnus 

 (Iwai and Nakamura 1964b:22, fig. 1; de Sylva 

 1955:21, fig. 40), Scomberomorus (Mago Leccia 

 1958:327, pi. 12), and Rastrelliger (Gnanamuttu 

 1971:14, fig. 6). Within the Scomberomorini, the 

 most useful differences are in the number of gill 

 rakers. Most of the branchial bones bear patches 

 of tiny teeth. 



Basibranchials. — The three basibranchials 

 form an anteroposterior chain. The first and 

 second are about the same size and considerably 

 shorter than the third. The first is covered dorsal- 

 ly by the glossohyal. 



In lateral view the first basibranchial is nar- 

 rowest in the middle. In Scomberomorus, it is 

 short with a wide base where it joins with the 

 second basibranchial but it is much more elon- 

 gate in Acanthocybium and Grammatorcynus. 

 The second basibranchial has a prominent notch 

 in the ventral margin and a distinct groove 

 laterally which extends from the anteroventral 

 margin to the middorsal region of the bone. This 

 groove accepts the anterior end of the first hypo- 



branchial. The third basibranchial has an ex- 

 panded anterior end at its junction with the 

 second basibranchial and then tapers posteriorly. 

 A prominent groove is present anteriorly which 

 accepts the medial anterior end of the second 

 hypobranchial. A section of cartilage extends 

 posteriorly to articulate with the fourth and fifth 

 ceratobranchials . 



Hypobranchials. — Three hypobranchials are 

 present. The first is interposed between the sec- 

 ond basibranchial and the first ceratobranchial. 

 The second hypobranchial is about the same size 

 as the first, fits into a groove on the third basi- 

 branchial, and extends to the second cerato- 

 branchial. The third hypobranchial is smaller 

 than the first or second, fits snugly against the 

 posterolateral margin of the third basibranchial 

 and its posterior end articulates with the third 

 ceratobranchial. 



Ceratobranchials. — The five ceratobranchials 

 are the longest bones in the branchial arches. 

 They have a deep groove ventrally for the bran- 



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