FISHES OF HAWAIIAN ISLANDS. 
109 
spines, which are later absorbed and lost; gill-openings very wide, the membranes not united, free 
from the isthmus; gillrakers usually long; pseudobranchiae present, large; gills 4, a slit behind the 
fourth; branch iostegals 7; dorsal fins 2, the first of rather weak spines, depressible in a groove, the 
second similar to the anal ; the elevated anterior lobe always distinct; anal spines weak; last rays of 
dorsal and anal detached and separate, forming in each case a series of finlets; caudal peduncle 
extremely slender, keeled, the caudal lobes abruptly diverging, falcate, the fin adapted for rapid 
motion; ventral fins well developed, thoracic, i, 5; vertebrae in greater number than in Carangidtc, 
the number ranging from 31 to 66; first upper pharyngeal present without teeth, third and fourth 
coossified, with teeth; lower pharyngeals separate; stomach sac-shaped; pyloric coeca numerous; air- 
bladder small, sometimes absent. Coloration metallic, often brilliant, the prevailing shade steel-blue. 
Genera about 12; species about 60. Fishes of the high seas, many of them cosmopolitan, and all hav- 
ing a wide range; most of them are valued as food-fishes, the flesh being firm and oily, but sometimes 
coarse. 
a. Caudal peduncle without median keel on each side Scomber, p. 169 
an. Caudal peduncle with a median keel on each side; a small keel above and one below this. 
b. Dorsal spines 10 to 16; gills normal, the laminae not forming a network. 
c. Body scaleless, excepting about the lateral line and corselet. 
cl. Dorsals well separated, the interspace more than half head ..Aims, p. 170 
dd. Dorsals contiguous, the interspace more than 5 in head. Gymnosarda, p. 171 
cc. Body wholly covered with small scales, those on the corselet and lateral line sometimes larger. 
c. Vomer and palatines with villiform or sand-like teeth; body robust, not compressed; verte- 
bra 39 to 41 Germo, p. 174 
ee. Vomer toothless; palatines with a single row of rather strong, conical teeth; body elongate, 
slightly compressed; vertebrae 50 to 54 Sarda, p. 175 
- 66. Dorsal spines about 25; gills with the laminae forming a network Acanthocybium , p. 176 
Genus 97. SCOMBER Linnaeus. The Mackerels. ‘'Opelu.” 
Body fusiform, rather elongate, somewhat compressed; caudal peduncle slender, without median 
keel, but with 2 small keels on each side; mouth wide, with a single row of rather small, slender teeth 
in each jaw and on the vomer and palatines; maxillary slipping under the broad preorbital, a fleshy 
lobe on each side of lower jaw near its junction with maxillary; scales very small, not forming a corse- 
let; first dorsal of 9 to 12 feeble spines, separated from the second by an interspace greater than the 
base of the fin; second dorsal small, followed by 5 to 9 detached finlets; anal similar to second dorsal, 
with similar finlets; pectorals and ventrals small, the former placed high, on the level of the eyes; 
caudal fin small, widely forked; pyloric appendages exceedingly numerous; air-bladder small or want- 
ing; vertebrae normally formed, 14+17=31; gillrakers long and slender. Species few, widely distri- 
buted, usually swimming in large schools; carnivorous and migratory; everywhere highly valued for 
food. 
Scomber Linnaeus, Syst. Nat., Ed. X, 297, 1758 ( scombrus ). 
Cordylus Gronow, Cat., 163, 1854 (scombrus). 
Pneumatophorus Jordan & Gilbert, Proc. U. S. Nat. Mus., V, 1882 (Apr. 25, 1883), 593 {pneumatophorus) . 
123. Scomber japonicus Houttuyn. 11 Opelu palaliu;” Chub Mackerel. Fig. 62. 
Head 3.9 in length; depth 5; eye 3.75 in head; snout 3. 1; maxillary 2.9; mandibl 2; interorbital 
4.5; 1 ). ix-i, 12-v; A. i-i, 11-v; scales 16-210-34; gillrakers 13+20, with long, slender, sparse teeth 
on anterior edge, the longest gillraker 1.4 in eye. 
Body slender, not compressed, the dorsal outline gently elevated; caudal peduncle not compressed 
and not keeled; head long; snout very long and pointed, the outline from tip to nape straight; mouth 
large, slightly oblique, the jaws subequal; maxillary reaching near anterior edge of pupil; a single row 
of small teeth of uniform size in each jaw; similar teeth on vomer and palatines; no teeth on tongue; 
eye large, strongly adipose; preopercle broad; no blunt teeth or spines on shoulder-girdle; scales very 
small, covering entire body, deciduous, not forming a corselet; top of head with a large, translucent 
area; no groove connecting dorsals; first dorsal higher than long; origin of anal slightly behind that of 
soft dorsal; pectoral short, not reaching tips of ventrals, 2.3 in head; ventrals 2.6 in head. 
Color in alcohol, bluish above, with about 30 wavy, darker blue streaks which reach just below 
