364 BULLETIN 189, UNITED STATES NATIONAL MUSEUM 



teeth on palatines; gill rakers slender, a little shorter than eye, 24 to 

 28 on lower and 11 to 13 on upper Umb of first arch; lateral line more 

 or less wavy; scales too small to enumerate accurately, shghtly en- 

 larged in pectoral region, about 19 to 24 rows between second dorsal 

 and lateral line; first dorsal composed of slender spines, the third and 

 fourth generally of nearly the same length, about equal to postorbital 

 part of head, origin of fin about an eye's diameter behind base of 

 upper ray of pectoral, its distance from tip of snout 2.6 to 2.75 in 

 length; second dorsal small, with slightly concave margin, densely 

 scaled in large specimens, its origin over or a Httle in advance of vent, 

 followed by 5 finlets, the last one the longest; caudal with two low 

 keels on base, its middle section densely scaled in large specimens; 

 anal preceded by a short stiff detached spine, the rest of fin similar 

 to second dorsal, also followed by 5 finlets; ventral moderate, inserted 

 slightly in advance of origin of first dorsal, distance from its base to 

 tip of mandible 2.6 to 2.8 in length, length of fin 2.3 to 2.9 in head; 

 pectoral short, upper rays longest, 2.2 to 2.7 in head. 



Color dark blue above; silvery below. Some specimens with dis- 

 tinct wavy bands on back, generally extending down the side to 

 lateral fine; the bands very indistinct in other specimens; and broken 

 up into spots in still others. Most of the large specimens with dark 

 spots on side below lateral line, these missing in all the smaller speci- 

 mens, which also lack the bars. Ventral and anal fins pale; other 

 fins more or less dusky; pectoral fin black at base, darkest on inner 

 side. 



The Mission secured 30 specimens, 110 to 355 mm. (92 to 295 mm. 

 to base of caudal) long. The 5 smallest ones were seined; all the 

 others were caught with hand lines. They are from Sechura Bay, 

 Callao, Pachacamac Island, and Chilca Bay. 



It is stated in the report of the Mission (1943, p. 268) that "lacaballa" 

 "is taken in some quantity but is used exclusively for drying and 

 salting since it is not highly regarded as a fish for fresh consumption. 

 The mackerel, like the bonito, is an inshore species and is not taken 

 in waters of the oceanic type. The great bulk of mackerel caught in 

 Peru is taken with hand lines baited with small pieces of fish." 



The Peruvian specimens are very close to Oriental ones, with which 

 some authors have identified them. However, Jordan and Hubbs 

 (1925, p. 211) have shown minor differences in the length of the head, 

 snout, and upper jaw, in the distance from tip of snout to origin of 

 first dorsal, and in the distance from tip of mandible and base of 

 ventral. Most of the differences indicated by the authors named 

 seem valid according to specimens examined. The following propor- 

 tions, based on two specimens of P. japonicus (Houttuyn) from Japan, 

 may be compared with those based on specimens from Peru used in 

 the description: Head 3.75, 3.8; snout 3.2, 3.4; distance from snout to 



