FISHERY BULLETIN: VOL. 82, NO. 4 



Scomberomorus (Fig. 40a, b) but this shelf is 

 absent in Acanthocybium (Fig. 40c) and Gram- 

 matorcynus (Fig. 40d). A variably sized notch is 

 present at the middle of the posterior edge of the 

 flat body of the bone. Grammatorcynus has a 

 prominent, anteriorly directed spine on the ven- 

 tral margin of the median process about one-third 

 of the distance from the body of the bone to the 

 anterior tip of the process. In Acanthocybium, 

 there is a separate process extending anteriorly 

 from the ventral wall of the median process. This 

 auxiliary process (Kishinouye 1923) is as long or 

 almost as long as the median process itself. It 

 ends in a series of several pointed processes. 

 (Both Conrad 1938 and Devaraj 1977 referred to 

 the auxiliary process as the median process.) 



The lengths of the median and lateral processes 

 vary among the species under discussion. To 

 compare the species quantitatively, we made two 

 sets of measurements and divided them by the 

 total length of the posttemporal, from the ante- 

 rior tip of the median process to the posterior 

 margin of the bone. We measured to the tips of 

 the median and lateral processes from the most 

 posterior point on the shelf between the two 

 processes. Largely because of the lack of a shelf 

 between the processes in Acanthocybium and 

 Grammatorcynus , both processes appear to com- 

 prise a larger proportion of total posttemporal 

 length than they do in the species of Scombero- 

 morus, 53-65% vs. 36-51% for the median process 

 and 27-40% vs. 15-36% for the lateral process. 

 The median process is longer in Acanthocybium 

 than in Grammatorcynus, 56-65% vs. 53-60%, 

 but the lateral process is slightly longer in Gram- 

 matorcynus than in Acanthocybium, 35-40% 

 vs. 27-37%. Among the species of Scomberomo- 

 rus, the longest median processes (48-51% total 

 length) are found in S. commerson, plurilineatus , 

 and sierra; the shortest (36-40%) in cavalla, 

 semifasciatus, and sinensis. The longest lateral 

 processes are in koreanus (36%) and plurilinea- 

 tus (30-31%); the shortest (15-19%) in cavalla, 

 munroi, niphonius, queenslandicus, and tritor. 



To eliminate the confounding factor of the shelf 

 between the median and lateral processes, mea- 

 surements also were made on the inner surface of 

 the bone, from the point where the two processes 

 diverge to the tips of the processes. Measured this 

 way, the longest median processes (74-79% of 

 total length of the posttemporal) are in Acantho- 

 cybium and six species of Scomberomorus. The 

 shortest median processes (63-68%) are in three 

 species of Scomberomorus: multiradiatus, ni- 



phonius, and semifasciatus. Grammatorcynus 

 also has a short median process (66-71%). Mea- 

 sured this way, the longest lateral processes are in 

 koreanus (53-55%), sierra (52%), plurilineatus 

 and regalis (50-51%), guttatus (49-55%), and 

 Grammatorcynus (48-52%). The shortest lateral 

 processes are in munroi (37-40%), tritor (41-42%), 

 and cavalla and niphonius (41-44%). Acantho- 

 cybium also has a relatively short lateral process 

 (42-51%). 



Still another way of comparing relative lengths 

 of the processes among species is to divide the 

 length of the lateral process by the length of the 

 median process, both measured on the inner 

 surface of the posttemporal. By this technique, 

 relatively greater proportional measurements of 

 the lateral processes are found in S. koreanus 

 (75-77% of median process), S. semifasciatus 

 (76%), Grammatorcynus (71-74%), S. multiradia- 

 tus (70-73%), and S. guttatus (69-71%). Relatively 

 shorter proportional measurements of these lat- 

 eral processes (55-63%) are found in Acantho- 

 cybium and five species of Scomberomorus: ca- 

 valla, munroi, niphonius, queenslandicus, and 

 tritor. 



Another difference lies in the presence and, if 

 present, in the shape of a spine or process at the 

 base of the lateral process on the inner surface of 

 the posttemporal. It appears to be absent in seven 

 species of Scomberomorus: cavalla, guttatus, 

 maculatus, queenslandicus, regalis, semifascia- 

 tus, and tritor. It is small and inconspicuous in 

 six species: brasiliensis , concolor, koreanus, line- 

 olatus, multiradiatus, and sierra. It is broader, 

 usually shaped more like a shelf with a point in 

 the remaining five species of the genus: commer- 

 son, munroi, niphonius, plurilineatus, and some- 

 times in sinensis. The process has the form of 

 a wide flap in Grammatorcynus and of a long 

 blunt process in Acanthocybium. Devaraj's (1977) 

 data for Indian species correspond well with 

 ours. 



Supracleithrum 



The supracleithrum (Fig. 41) is an ovate bone, 

 overlapped dorsolaterally by the posttemporal 

 and overlapping the anterior part of the dorsal 

 winglike extension of the cleithrum. The anterior 

 border of the bone on the mesial side is thickened 

 into a ridge. Dorsally there is a small handle- 

 shaped process which curves into the posterior 

 margin to end in a notch at the posterodorsal 

 aspect. A branch of the lateralis system extends 



604 



