122 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Vertebrae in greater number than in the Carangidse, the number ranging from 31 to 66. First upper 
pharyngeal present, without teeth; second with teeth; third and fourth coossified, with teeth; lower 
pharyngeals separate. Stomach sac-shaped. Pyloric caeca numerous. Air-bladder small, sometimes 
absent. Coloration metallic, often brilliant, the prevailing shade steel-blue. 
The Scombridx comprise about 12 genera and 60 species; of the 8 American genera only 2 are 
represented in Porto Rican waters. These fishes are inhabitants of the high seas, all having a wide 
range, and many of them being cosmopolitan. Most of them are valued as food-fishes, the flesh being 
firm and oily, but sometimes coarse. 
<i. Dorsal spines 10 to 16; gills normal, the lamin® not forming a network; teeth entire. 
b. Body scaleless, excepting about lateral line and corselet; abdominal vertebrae with their lower foramina enlarged 
and a portion between vertebrae proper and haemapophyses developed in form of a network or trellis, 
r. Dorsals well separated, interspace more than half head; corselet well developed; teeth small, some present on 
vomer, none on palatines; gillrakerslong, slender, and numerous; pectorals rather high; vertebrae 39. Auxis, 50 
cc. Dorsals contiguous, interspace more than 5 in head; palatine teeth villiform; pectorals low. 
d. Vomer toothless; dorsal spines 15 or 16; vertebrae 38 Gymnosarda 
lib. Body wholly covered with small scales, those on corselet and lateral line sometimes larger; dorsal spines 14 to 26; 
vertebrae normally formed, not as in Auxis and Gymnosarda. 
c. Teeth of jaws slender, subconical, little, if at all, compressed; gillrakers numerous; corselet distinct; pectoral 
inserted low. 
/. Vomer and palatines with villiform or sand-like teeth; body robust, not compressed; vertebrae 39 to 41. 
g. Pectoral short, not reaching much beyond tip of the moderate ventral; size enormous Thonnus 
gg. Pectoral very long, ribbon-shaped, reaching much beyond front of anal; size moderate Germo 
J'f. Vomer toothless; palatines with a single row of rtither strong, conical teeth; body elongate, slightly compressed; 
vertebrae 50 to 54 Sarda 
ce. Teeth of jaws strong, subtriangular or knife-like, more or less compressed; villiform teeth on vomer and palatines; 
gillrakers comparatively few; corselet obscure; pectorals inserted near level of eye; dorsal'spines 14 to 18; 
body elongate, compressed; head short; snout short; vertebree 45 Scomberomorus, 51 
Acanthocybiinie: 
aa. Dorsal spines about 25; gills with laminse forming a network, as in Xiphias-, teeth large, compressed, serrated. 
h. Dorsal spines 24 to 26; body elongate, fusiform; snout long; vertebrae 32 + 34 = 66 Acanthocybium 
Genus 50. AUXIS Cuvier. The Frigate Mackerels. 
Body oblong, plump, mostly naked posteriorly, anteriorly covered with small scales, those of 
pectoral region enlarged, forming a corselet. Snout very short, conical, scarcely compressed. Mouth 
rather small, jaws equal. Teeth very small, mostly in a single series, on jaws and vomer only. Tail very 
slender, depressed, with a rather large keel on each side. First dorsal short, separated from second by a 
considerable interspace. Second dorsal and anal small, each with 7 or 8 finlets. Pectorals and 
ventrals small. No air-bladder. Branchiostegals 7. Pyloric caeca dendritical. Gillrakers very long 
and slender, numerous. Vertebrae 39 in number, peculiarly modified, essentially as in Gymnosarda. 
One pelagic species, widely distributed. 
79. Auxis thazard (Lacepede). “Albacora” ; Frigate Mackerel. 
Head 3.8; depth 4.4; eye 6; snout 3.7; mandible 2.2; interorbital 3.2; D. x-12-vm; A. 13-vn; 
pectoral 1.8; ventral 2.25; caudal 1.4. 
Body elongate, robust, scaleless, save for a corselet of moderate and very small scales about 
