186 FISHES OF NORTH CAROLINA. 



jaws; unarmed opercle; wide gill-openings; gill-membranes unconnected, and 

 free from the isthmus; long gill-rakers; large pseudobranchise; 4 gill-arches; 

 7 branchiostegals; 2 dorsal fins, the anterior of weak spines, the posterior like the 

 anal; posterior rays of dorsal and anal fins separated and known as finlets; caudal 

 peduncle slender and keeled; caudal fin large and forked; stomach sac-shaped^ 

 with numerous ca^ca; air-bladder small or absent; color usually blue above, with 

 metallic sheen. Eight genera and 15 species are represented in American waters; 

 and of these 6 genera and 8 species are known from North Carolina. Doubtless 

 other wide-ranging species have from time to time been taken on the North 

 Carolina coast and may be looked for again. The common mackerel {Scomber 

 scomhrus) of the Middle Atlantic and New England coast, the most valuable 

 member of the family in American waters and also in the world, is first met with 

 in spring off Cape Hatteras, but is not common in the inshore waters. 



Key to the North Carolina genera of mackerels, 

 i. Caudal peduncle with a median keel on each side, with a smaller keel above and below this. 

 a. Body without scales, except on lateral line and corselet. 



b. Dorsal fins separated by more than half length of head; dorsal spines 10; teeth on 



vomer, none on palate bones Auxis. 



66. Dorsal fins separated by a space less than .2 length of head; dorsal spines 15; teeth 



on palate bones, none on vomer Gymnosarda. 



aa. Body entirely covered with small scales. 



c. Jaw teeth slender; gill-rakers numerous; pectoral fins placed low. 



d. Vomer and palate bones with villiform teeth; body robust, size very large. 



Thunnus. 

 dd. Vomer without teeth; palate bones with a single row of strong conic teeth; body 



elongate, size small Sarda. 



cc. Jaw teeth strong, triangular or knife-like; gill-rakers few; pectoral fins inserted near 



level of eyes Scomberomorus. 



n. Caudal peduncle without median lateral keels Scomber. 



Genus AUXIS Cuvier. Frigate Mackerels. 

 Small scombrids, intermediate in form between the common mackerel and 

 bonito, with elongate, plump body, destitute of scales except along lateral line 

 and in region of pectoral and ventral fins; small mouth, very small jaw teeth 

 mostly in single series, short snout; slender, depressed peduncle with strong 

 lateral keel; small fins, the second dorsal and anal especially so; long and num- 

 erous gill-rakers. The single species is pelagic, swims in large schools, and is very 

 erratic in its movements. {Auxis, ancient Greek name for the young tunny.) 



159. AUXIS THAZARD (Lacepede). 



"Bonito"; Frigate Mackerel. 



Scomber thazard Lac^pfede, Histoire Naturelle des Poissons, iii, 9, 1802; coast of New Guinea. 

 Auxis thazard, Jordan & Evermann, 1896, 867, pi. cxxxiii, fig. 365. 



Diagnosis. — Body very slightly compressed, its depth a little less than .25 total length; 

 head .25 length, the snout conic; maxillary bone beneath the preorbital and almost concealed 

 by it; eye .2 length of head, equal to snout; gill-rakers on lower limb of first arch about 33; 

 dorsal fins separated by a space nearly equal to length of head, the rays x + 12, with 7 or 8 

 finlets; anal rays 13, with 7 or 8 finlets. Color: back blue with darker vermiculations; sides 

 and below silvery white, {thazard, from the French tassard, a name given to fishes Uke 

 the Spanish mackerel.) 



