FISHES OF EL SALVADOR 
269 
quality of the flesh is excellent. They are chiefly shore fishes, frequenting brackish 
water, and some of them ascend fresh-water streams. Three species were secured 
in fresh water in El Salvador; others, no doubt, occur there from time to time. 
KEY TO THE SPECIES 
a. Scales small, 72 to 75 in a lateral series, about 8 rows between the middle of second dorsal 
and lateral line; gill rakers few, about 8 on lower limb of first arch nigrescens, p. 269. 
aa. Scales larger, not more than 65 in a lateral series, 5 or 6 rows between middle of second dorsal 
and lateral line; gill rakers more numerous, not fewer than 12 on lower limb of first arch. 
b. Scales moderate, 52 to 54 in a lateral series; gill rakers numerous, 16 or 17 on lower limb 
of first arch; angle of preopercle with 2 abruptly enlarged serrse; lateral line not in a 
dark streak robaliio, p. 270. 
bh. Scales smaller, 58 to 62 in a lateral series; gill rakers fewer, 13 or 14 on lower limb of first 
arch; angle of preopercle with several gradually enlarged serrse; lateral line in a black 
streak pectinatus, p. 271. 
14. Centropomus nigrescens (Giinther) 
ROBALO; ROVALO 
Centropomus nigrescens Giinther, Proc, Zool. Soc, London, 1864, 144, and Trnns., Zool. Soc, London, VI, 1868, 407 ("Chiapam ", 
Pacific coast of Guatemala); Jordan and Evermann, Bull., V. S. Nat. Mus., XLVII, 1890, 1119; Regan, Biol. Cent. Amer., 
Pisces, 1907, 50; Meek and Ilildebrand, Pub., Field Mus. Nat. Hist., Zoiil. Ser., XV, Part II, 1925, 426, PI. XLII. 
Centropomns viridis Lockington, Proc., Cal. Ac. Sci., VII, 1876 (1877), 110 (Off Ascunsion Island). 
Centropomus undecimalis (not of Bloch) Gilbert and Starks, Memoir., Cal. Ac. Aci., IV, 1904, 89. 
Head 3 to .3.1; depth 3.7 to 3.85; D. ^TII-I, 9; A. Ill, G; scales 72 to 75. 
Body elongate, compressed; profile concave over eyes; caudal peduncle long, 
its least depth 2.75 in head; head long; snout broad, its length, 3.36 to 3.6 in head; 
eye 7.55 to 9; interorbital 4.75; mouth large, oblique; lower jaw strongly projecting; 
maxillary reaching nearly opposite middle of eye, 2.25 to 2.3 in head; preorbital 
with a few small serrje; preopercle strongly serrate, several serrje at angle enlarged; 
preopercular ridge without spines; gill rakers rather long and few, 8 on lower limb 
of first arch; scales rather small, about 8 rows between middle of base of second 
dorsal and lateral line, not greatly reduced in advance of dorsal, small scales extend- 
ing on base of all fins, except spinous dorsal; origin of spinous dorsal nearly twice 
the diameter of eye behind base of pectorals, the spines moderate, the third and 
fourth of about equal length, the former not reaching the tip of the latter when 
deflexed, the length 2.05 to 2.5 in head; origin of second dorsal notably nearer base 
of caudal than preopercular margin; caudal fin forked, both lobes rather acute; 
origin of anal under middle of base of second dorsal, the second spine somewhat 
enlarged, not reaching the tip of the third when deflexed, 2.75 to 3.25 in head; 
ventral fins inserted about an eye's diameter behind base of pectorals, failing to 
reach vent; pectoral fins reaching about to the beginning of the distal third of 
ventrals, 1.9 to 1.95 in head. 
Color of a fresh specimen, 715 millimeters long, bluish silvery above; lower 
part of sides and abdomen silvery; upper surface of head and sides in advance of 
pectorals yellomsh; lateral line in a black streak; dorsals, caudal, and anal bluish 
black; second dorsal, caudal, and anal with pale margins; pectorals and ventrals 
yellowish green; ventrals with a broad white margin. 
