FISHERY BULLETIN: VOL. 82, NO. 4 



a 



Grammatorcynus and most species of Scomber- 

 omorus. Devaraj (1977:34) stated that the poste- 

 rior margin was convex in S. commerson and 

 Acanthocybium. We find it to be nearly straight 

 in Acanthocybium and very slightly concave in 

 S. commerson. The concave posterior border 

 makes the upper and lower parts appear as two 

 limbs, the lower of which is longer. As Devaraj 

 (1977:34) noted, the lower portion is longer in S. 

 guttatus than in the other species, the distance 

 from the anterior margin of the bony ridge to the 

 posterior end of the lower lobe being 74-80% of 

 the height of the preopercle measured from the 

 ventral margin to the dorsal tip of the bone. 

 Other species with long lower portions include S. 

 munroi (73-78%), S. plurilineatus (69-79%), S. 

 niphonius (73-75%), and Grammatorcynus (68- 

 75%). Devaraj (1977:34) stated that the anterior 

 ridge was forked at its upper part in all the 

 Indian species of Scomberomorus except S. com- 

 merson in which the fork is either indistinct 

 or absent, and that the fork was completely ab- 

 sent in Acanthocybium. We are unable to con- 

 firm this observation and find no differences 

 between Scomberomorus and Acanthocybium. In 

 these genera, and in Grammatorcynus , the an- 

 terodorsal margin terminates in a pore similar to 

 the preopercular lateral line canal pore at the 

 anteroventral margin of the bone. 



FIGURE 33. — Left preopercles in lateral view. a. Scomberomo- 

 rus semifasciatus, New Guinea, 510 mm FL. b. Scomberomorus 

 multiradiatus , New Guinea, 294 mm FL. c. Acanthocybium 

 solandri, Revillagigedos Is., 1,068 mm FL. d. Grammatorcynus 

 bilineatus, Marshall Is., 424 mm FL. 



is thickened into a bony ridge. A series of 5-7 

 pores along the lower margin of the ridge repre- 

 sents the preopercular canal of the lateral line 

 system which continues into the dentary On the 

 mesial side, the ridge possesses a groove for 

 attachment to the hyomandibula and the quad- 

 rate. There is a shelf mesial to the anteroventral 

 end of the preopercle in Acanthocybium (Fig. 

 33c) that is not present in Scomberomorus (Fig. 

 33a, b) or Grammatorcynus (Fig. 30d). Devaraj 

 (1977:34) referred to this as a groove. The canals 

 leading to the preopercular pores are visible 

 through the bone in Scomberomorus and Gram- 

 matorcynus but cannot be seen in Acanthocybium 

 due to the thickness of the bone. The posterior 

 margin of the preopercle is distinctly concave in 



Subopercle. — The subopercle is a flat triangu- 

 lar bone with a prominent anterior projection 

 (Fig. 34). Two ridges converge posteriorly from 

 the anterior projection on the lateral side of the 

 bone. The upper ridge articulates with the lower 

 posterior projection of the opercle and the lower 

 ridge connects to the posterodorsal margin of the 

 interopercle. The dorsal ridge is much stronger 

 than the ventral ridge and extends over the main 

 part of the subopercle as a discrete shelf. The 

 much weaker ventral ridge is difficult to detect in 

 some species. The angle between the anterior 

 projection and the anterior margin of the sub- 

 opercle varies from approximately a right angle 

 in Acanthocybium (Fig. 34c) and most species of 

 Scomberomorus to acute in Grammatorcynus 

 (Fig. 34d) and Scomberomorus multiradiatus 

 (Fig. 34b). The length of the anterior projection 

 varies from 20 to 45% of the length of the anterior 

 margin dorsal to the projection. The projection is 

 longest in Acanthocybium (36-45%), S. sierra 

 (37-43%), and S. koreanus (33-41%). It is shortest 

 in S. commerson (20-25%), S. semifasciatus 

 (21-23%, Fig. 34a), and S. queenslandicus (21- 



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