FISHES OF HAWAIIAN ISLANDS. 
67 
outer rays prolonged; dorsal fin inserted at middle of body or absent; anal short; caudal forked; gill- 
openings very wide; gill-laminae well developed, separate from each other; gillrakers long; pseudo- 
branchiae none. Deep-sea fishes. 
Bathypterois Gunther, Ann. and Mag. Nat. Hist. 1878, 5th series II, 183 ( lonijifilis ). 
Synapteretmus-G oode & Bean, Oceanic Ichth., 64, 1896 (quadrifilis). 
The single Hawaiian species of this family is fully described in Section II. 
Family XX. MYCTOPHIDtE.— T he Lantern Fishes. 
Body oblong or moderately elongate, more or less compressed, covered with scales which are 
usually cycloid, but sometimes ctenoid; mouth wide; entire margin of upper jaw formed by the long 
and' slender premaxillaries, closely adherent to which are the slender maxillaries; teeth various, 
mostly villiform, in bands in the jaws, also on the pterygoids, palatines, and tongue, and on the vomer 
in adults; no barbels; gill-membranes separate, free; branch iostegals 8 to 10; pseudobranehise well 
developed; gillrakers long and slender; lateral line usually present; scales prominent and often 
enlarged; cheeks and opercles scaly; adipose fin present; dorsal fin short, median, of soft rays; pecto- 
rals and ventrals present; anal fin moderate; caudal forked; air-bladder small; intestinal canal short; 
luminous spots or photophores more or less regularly placed along sides of body; larger luminous 
glands often present on head or on caudal peduncle. 
Species about 100. Small fishes, very widely distributed in the open sea. They live away from 
the shoi'es, ordinarily at a considerable depth, coming to the surface at night or in stormy weather, 
descending by day. 
a. Dorsal fin long, ending not much, if any, before front of anal fin. 
b. Caudal photophores 4 or 3, never 2; dorsal fin not much longer than anal; body deep or slender, not much contracted 
behind; caudal peduncle robust; edge of preopercle more or less oblique. 
c. Head with large luminous glands before or below the eye Diaphus, p. 67. 
cc. Head without large luminous glands Nannobracliium, p. 67. 
bb. Caudal photophores 2, never 3 or 4; dorsal fin notably shorter than anal, its rays 9 to 14; anal rays 16 to 20; body 
deep anteriorly; caudal peduncle slender, edge of preopercle nearly vertical; pectorals long, placed high; 
no luminous glands on head; eye large. 
d. Scales cycloid; maxillary scarcely enlarged at tip; last rays of dorsal not behind first of anal. 
e. Snout prominent, projecting beyond tip of lower jaw; scales of lateral line more or less enlarged; caudal 
peduncle very slender; usually a luminous gland on its upper surface. 
/. Lateral line well developed Rhinoscopelus, p. 68. 
ff. Lateral line none Centrobranchus, p. 69. 
ee. Snout little prominent, scarcely projecting beyond tip of lower jaw; scales of lateral line usually not enlarged; 
no luminous glands on upper edge of tail; moderately elongate Myctophum, p. 69. 
dd. Scales ctenoid, firm; tail with a luminous gland above JDasyscopelus, p. 69. 
aa. Dorsal and anal short, similar, far apart Neoscopelus, p. 69. 
Genus 28. DIAPHUS Eigenmann & Eigenmann. 
This genus is closely related to JEtkoprora, its chief character being the division of all or nearly all 
of the photophores by a horizontal cross-septum of black pigment, giving them the form of the Greek 
letter L, theta. This septum is readily injured or destroyed in badly preserved specimens, and per- 
haps all species called JEthoprora have it. Of the 5 known species 3 have been taken in Hawaiian 
waters, and are described in Section II. 
Diaphus Eigenmann & Eigenmann, Proc. Cal. Ac. Sci., 2d series, III, 1890, 3 (theta). 
? JEtkoprora Goode & Bean, Oceanic Icthth., 86, 1896 (metopoclampa) . 
? Colleltia Goode & Bean, Oceanic Ichth., 83, 1896 ( rafinesquei ) 
Genus 29. NANNOBRACHIUM Gunther. 
This genus is closely allied to Lampanyctus, from which it differs chiefly in the small pectorals. 
Caudal peduncle with luminous blotches above and below; photophores small, arranged as in 
Lampanyctus; scales of lateral line enlarged in all species, so far as known; last ray of dorsal more or 
less behind front of anal. Several species, only one Hawaiian ( Nannobracliium nigrum) described 
in Section II. 
Nannobracliium Gunther, Deep-sea Fishes Challenger, 199, 1887 (nigrum). 
Stenobrachius Eigenmann & Eigenmann, Proc. Cal. Ac. Sci., Ill, 1890, 5 (leucopsarum) . 
