FISHERY BULLETIN: VOL. 73, NO. 3 



longest and narrowest rostra among bonitos. The 

 dorsal process above the rostrum seems to vary 

 considerably inter- and intraspecifically (see Kuo 

 1970, fig. 7). 



The sagittae of Gymnosarda are distinct from 

 those of all other bonitos by their extreme curva- 

 ture when viewed in situ from above, by their 

 concave ventral margin (sagittae of all other 

 bonitos have relatively straight ventral margins), 

 and by the fact that except for minor pro- 

 tuberances and other irregularities the dorsal 

 margin, in the posterior half of the otolith, roughly 

 parallels the ventral margin, giving a sameness of 

 height to the otolith in this region. The sulcus is 

 more distinctive on the inner surface. The 

 posterior dorsal margin is deeply serrate. No 

 pyramidlike ridge is present in the middle of the 

 posterior half. Laterally, the deepest part of the 

 sagitta is in front of the middle of the posterior 

 half. 



The sagitta of Allothunnus is small and similar 

 in size to the species of Sarda. It has a very dis- 

 tinctive triangular outline; with an acute 

 posteroventral angle and no prominent ridges on 



the outer surface. The inner surface of the sagitta 

 has a deep sulcus with a very prominent dorsal 

 ridge. 



Branchiocranium 



The branchiocranium is divided into five sec- 

 tions: mandibular arch, palatine arch, hyoid arch, 

 opercular apparatus, and branchial arch. 



MANDIBULAR ARCH.-The mandibular arch 

 is composed of the upper jaw (premaxilla, maxilla, 

 and supramaxilla) and the lower jaw (dentary, 

 angular, and retroarticular). Teeth are borne on 

 the premaxilla and dentary, and the number of 

 teeth on these bones is a useful taxonomic 

 character. 



Dentition. -Conical teeth are present on the 

 upper and lower jaws in all bonitos. These teeth 

 differ from the laterally compressed teeth with 

 serrate edges found in Spanish mackerels 

 (Scomberomorini) and are generally larger than 

 the tiny conical teeth of the higher tunas (Thun- 

 nini). In addition to jaw and palatine teeth. 



Table 5.-Number of teeth in the upper jaw in species of Sardini. (Mean of left and right sides rounded off upwards to nearest whole 



number.) 



554 



