separated from each other by ridges of bone. 

 Thus, there are six grooves and five ridges in all. 

 The median ridge is carried forward on the fron- 

 tals to the ethmoid and is prolonged posteriorly in 

 a large supraoccipital crest. This crest extends 

 down over the exoccipital suture more broadly 

 than in any other genus of the Scombridae. 



The internal ridge or temporal ridge almost 

 reaches anteriorly to the posterior portion of the 



FISHERY BULLETIN: VOL. 82, NO. 4 



nasal, and it is not interrupted above the eyes by 

 any transverse ridge. Posteriorly, the ridge ends 

 at the epiotic where the medial process of the 

 posttemporal attaches. 



The external or pterotic ridge extends forward 

 to the midlevel of the orbit and develops anterior- 

 ly a small auxiliary ridge that extends laterally 

 and posteriorly toward the temporal ridge. 



The dilator groove is shorter than the other two 



a 



FIGURE 12.— Skulls in dorsal view. 



562 



a. Scomberomorus koreanus, Singapore, 480 mm FL. 

 California, 495 mm FL. 



b. Scomberomorus concolor, Gulf of 



