FISHERY BULLETIN: VOL. 82, NO. 4 



semifasciatus , Fig. 23a). The former possesses a 

 prominent knob at its dorsolateral aspect that fits 

 into the articular surface of the vomer and an 

 anterior, deep concavity facing the inner wall of 

 the premaxilla. The head is 18-25% of the total 

 length of the maxilla. Immediately posterior to 

 the head is a shallow depression which receives 

 the anterior articulating process of the palatine. 

 The shank of the maxilla is narrow and some- 

 what flattened. The posterior end expands into a 

 thin, flat plate which is partially covered dorsally 

 by the supramaxilla. The height of the plate is 8- 

 15% of the total length of the maxilla. Acantho- 

 cybium (Fig. 23c) and Grammatorcynus (Fig. 

 23d) lack any posterior expansion of the maxilla. 

 In fact, in Acanthocybium there is a notch in the 

 dorsal margin of the maxilla, and the posterior 

 end is distinctly lower than the middle of the 

 shaft of the bone. 



Scomberomorus munroi is the only species in 

 the genus that is distinguishable from the others 

 in characters of the maxilla; it totally lacks the 

 anterior process on the outer surface of the head 

 of the maxilla (Fig. 23b). Devaraj (1977:23) stated 

 that the outer process was "flimsier" in S. com- 

 merson, but we find that the process varies from 

 small to moderate in our material of the species 

 and that S. commerson is not distinct in this 

 aspect. 



The head of the maxilla is shorter than in most 

 other species, relative to total length of the max- 

 illa, in the six species of the S. regalis group. 

 Starting with the shortest maxilla head length 

 (lowest mean percent), these six species (plus 

 koreanus and multiradiatus ) rank as follows: 1) 

 concolor, 18.8; 2) brasiliensis , 19.0; 3) sierra, 

 19.8; 4) tritor, 19.9; 5) koreanus, 20.2; 6) macu- 

 latus, 20.6; 7) multiradiatus, 21.0; and 8) tritor, 

 21.1. The longest heads are found in niphonius 

 (24.7), semifasciatus (24.1), and lineolatus (24.0). 

 The head of the maxilla is a little longer, relative 

 to total maxilla length, in Grammatorcynus 

 (26%) and much longer (33%) in Acanthocybium. 



The posterior expansion of the maxilla is least 

 well-developed (lowest) relative to maxilla length 

 in S. multiradiatus (8-9%) and S. sinensis (9- 

 11%). The best-developed posterior expansion is in 

 S. plurilineatus (15%). The other 15 species range 

 from 11 to 14%. This range of variation is shown 

 in S. munroi but the specimen illustrated (Fig. 

 23b) shows a relatively well-developed posterior 

 expansion. The shape of the posterior expansion 

 varies within and between species, but most of 

 the expansion is usually ventral. 



Dentary. — The dentary (Fig. 24) is a large 

 forked bone which forms the major part of the 

 lower jaw. It is laterally flattened and bears a 

 single row of 4-37 compressed triangular teeth on 

 the dorsal margin. Posteriorly, the dentary forms 

 two arms. The ventral arm is relatively narrow 

 and shorter than the dorsal arm, and its inferior 

 margin has a groove which accepts the angular 

 and the anterior end of Meckel's cartilage. The 

 base of the ventral arm has an external series of 

 pores, which seem to be the preoperculomandibu- 

 lar pores (Allis 1903; Mago Leccia 1958) of the 

 lateral line system. The length of the dentary 

 from its anterior margin to the tip of the lower 

 arm is 86-97% of the length to the tip of the upper 

 arm. The figures are similar for Acanthocybium 

 (91-96%). However, the lower margin is longer in 

 Grammatorcynus, 105-109% of the length of the 

 upper margin (Fig. 24c). The proportions are 

 similar in all 18 species of Scomberomorus, with 

 S. maculatus having the shortest lower margin 

 (87-89%) and S. concolor the longest (92-97%). 



FIGURE 24. — Left dentaries in lateral view. a. Scomberomorus 

 semifasciatus. Port Moresby, New Guinea, 510 mm FL, 2 x . b. 

 Acanthocybium solandri, Miami, Fla., 1,403 mm FL, lx. c. 

 Grammatorcynus bilineatus, Marshall Is., 424 mm FL, 2 x . 



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