sis, narrowest in brasiliensis, caualla, and 

 commerson. 



Urohyal. — The urohyal (Fig. 31) is a com- 

 pressed, median, unpaired bone. The anterior end 

 of this element lies between, and is connected 

 with, the hypohyals of the left and right sides. 

 The dorsal and ventral margins are thickened. 

 The anterior end has an articulation head and 

 the posterior end is deep. The maximum depth 

 posteriorly is 13-24% of the length of the dorsal 

 margin. The urohyal is not as deep in Acantho- 

 cybium as in the species of Scomberomorus, 

 depth 13-15% of the length of the dorsal margin 



FISHERY BULLETIN: VOL. 82, NO. 4 



compared with 16-24%. Grammatorcynus also 

 has a low urohyal, depth 15-17% of length. The 

 length of the ventral margin is 68-91% of the 

 length of the dorsal margin. The ventral margin 

 of the urohyal does not extend as far posteriorly 

 in Grammatorcynus , only 68-69% of the length 

 of the dorsal margin compared with 80-91% in 

 Acanthocybium and Scomberomorus. Both Mago 

 Leccia (1958:322) and Devaraj (1977:32) stated 

 that the posterior end of the dorsal margin was 

 pointed but it ends in a distinct fork in all species 

 of Scomberomorus and in Acanthocybium (Fig. 

 31c). The major difference in Grammatorcynus is 

 that the shape of the posterior end of the dorsal 



FIGURE 31. — Urohyals in left lateral view. a. Scomberomorus queenslandicus , Queens- 

 land, 641 mm FL, 2x . b. Scomberomorus munroi. New Guinea, 512 mm FL, 2x. c. 

 Acanthocybium solandri , Indian Ocean, 1,088 mm FL, lx . d. Grammatorcynus bilineatus , 

 New Guinea, 382 mm FL, 3 x . Inset to right is the posterior end of the dorsal margin, in 

 dorsal view. 



588 



