370 BULLETIN 189, UNITED STATES NATIONAL MUSEUM 



Head 3.1 to 3.3; depth 3.4 to 3.7; D. XIV-13 to 15-VIII or IX; 

 A. II, 11 to 13-VIII, rarely IX; P. 33 to 35. 



Body moderately compressed, its greatest thickness often nearly 

 three-fourths its depth, tapering strongly posterior to second dorsal; 

 caudal peduncle strongly depressed, with a prominent lateral keel, 

 and a minute keel above and below it on base of caudal, its depth 

 11.8 to 13 in head; head compressed, quite convex above; snout 

 pointed, 3.0 to 3.4 in head; eye round, fairly large, 5.0 to 5.8; inter- 

 orbital 2.8 to 3.4; mouth moderately large, terminal, oblique; maxil- 

 lary with almost straight posterior margin, generally not quite reach- 

 ing opposite middle of eye, 2.5 to 2.7 in head; teeth in jaws in a single 

 series, rather small, pointed, curved inward; oval patches of villiform 

 teeth on vomer and palatines; gill rakers nearly as long as eye, some 

 of them often thickened at the end, their inner margins denticulate, 

 20 to 22 on lower and 7 to 9 on upper limb of first arch; lateral line 

 wavy; scales on body minute, forming a more or less distinct corselet 

 in region of pectorals; first dorsal high anteriorly, the first and second 

 spines longest, about as long as snout and two-thirds the eye, decreas- 

 ing rapidly in length behind third spine, origin of fin about over in- 

 sertion of pectoral, its distance from tip of snout 2.9 to 3.1 in length; 

 second dorsal elevated anteriorly, the lobe becoming very long in 

 large specimens, 2.2 to 2.6 in head in the rather small specimens at 

 hand; origin of anal about under end of dorsal; anterior lobe of anal 

 generally scarcely as high as that of dorsal, 2.2 to 2.8 in head; ventral 

 moderately small, 2.4 to 2.7 in head, its distance from tip of mandible 

 2.75 to 3.0 in length; pectoral large, reaching to or more usually 

 beyond origin of second dorsal, nearly or quite as long as head, 3.3 

 to 3.6 in length. 



Color very dark blue above, merging into the dirty gray or silver 

 of lower parts of side; region around ventrals white; lower half or so 

 of side with nearly vertical, sometimes curved pale silvery streaks, 

 some of them broken into spots; dorsal, caudal, and pectoral fins more 

 or less dusky, the pectoral quite dark on inner side; second dorsal and 

 anal each with a black margin; finlets yellow, conspicuously margined 

 with black; ventral largely white on outer side, dusky on inner side. 



The proportions and enumerations used in the foregoing description 

 are based on 12 specimens, 545 to 790 mm. (471 to 650 mm. to base 

 of caudal) long, furnished by the Mission. These fish were caught 

 with trolling lines, 25 miles southwest of Fraile Point; 9 miles west of 

 Palominos Rocks, off Callao; and off Lomas Point. The report of 

 the Mission (1943, p. 228) stated that tunas were caught during every 

 month of the investigation (February to September 1941) from 

 Cabo Blanco to Ilo, though not in water cooler than 17° C. They 

 were caught near shore and also offshore; the presence of food and the 

 temperature of the water apparently governed their movements. 



