CARANGIDAE 39 



Though the supraoccipital widely covers the greater part of the 

 suture between the frontals, they meet below it for their full length. 

 They form the anterior part of the supraoccipital crest, carrying it to 

 the ethmoid. In this portion of the crest, especially when the crest is 

 thin, there is often no trace of a suture between the frontals. The 

 suture is, however, always evident on the lower surface of the frontals 

 within the orbital cavity, and in a fresh or well macerated specimen 

 the frontals may be separated through the crest. 



No portion of the ethmoid shows in the orbital cavity between the 

 prefrontals except in Chloroscombrus, where a very small portion of it 

 shows in this region at the upper part of the prefrontal suture. 



In Seriola the ethmoid is very broad, and for convenience may 

 be described as consisting of two portions. The superior portion is a 

 broad plate, concave in front, and directly from under it medially a 

 blunt keel on the inferior portion projects downward and forward. 

 Megalaspis, Elagatis, Oligoplites, Scomberoides and Naucrates are es- 

 sentially the same, but in the last three the inferior portion is sharper 

 in front and descends more abruptly, not projecting much forward. In 

 Gnatlianodon, Citula, Tracliurops, CMoroscombrus and Caranx, the su- 

 perior portion is concave in front, but very narrow (only slightly so in 

 Caranx}, and just below it is a cup-shaped depression replacing the 

 keel, which is only developed at the lower end near the vomer remote 

 from the superior portion. Decapterus is somewhat between these two 

 conditions; the superior portion is very narrow, with only an indica- 

 tion of a concave front, and the keel of the lower portion, though not 

 in intimate relation with the superior portion, is not separated from it 

 by a depression. In Trachinotus and Alectis the superior portion is 

 produced, moderately narrow, convex in front, and with a keel about 

 as in Decapterus. Trachurus, Selene and Vomer are of the same type 

 as the last, but with the superior portion scarcely, or not at all, 

 widened. These conditions, though marked in the extremes, merge more 

 or less with each other. 



The prefrontals meet broadly behind the ethmoid in front of the 

 orbital cavity. They are pierced by the olfactory nerve. Usually they 

 form a broad outstanding mass on each side, angulated below and hav- 

 ing an articular surface on their lower edge for the palatine, but in 

 Selene they are gently rounded in outline, and ascend nearly straight to 

 the frontals without an angle. On the anterior surface of each pre- 

 frontal at the side of the ethmoid, and often assisted by the latter, a 

 cavity is formed in many examples. In Elagatis the cavity is partic- 

 ularly shallow, but very wide and long. The frontal reaches far over it, 



