54 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
KEY TO THE FAMILIES OF FISHES REPRESENTED IN WEST INDIAN WATERS . 1 
I. — Ventral Fins Present, Abdominal. 
A. Back with an adipose fin behind the single-rayed dorsal fin. 
B. Head with 4 to 8 long barbels about the mouth and nostrils Sinjp.in.-E. 
BB. Head without barbels as described above. 
C. Sides of body without photophores or luminous glands; no barbel at throat. 
D. Pseudobranehiee present. 
E. Maxillary very narrow, rudimentary, or obsolete; hypocoracoids not divergent Synodontida. 
EE. Maxillary well developed, dilated behind; pectoral normal; hypocoracoids mostly divergent Aulopida. 
DD. Pseudobranchiae absent. 
F. Pectoral* undivided, subhumeral; pseudobranchise absent Benthosaurida. 
FF. Pectoral rays elongate, arranged in two groups Bathypteroididac. 
CC. Sides of body with photophores more or less developed. Barbel at throat present, very long; body naked. 
Astronesthida. 
G. Vertebral spines projecting through skin of back before dorsal fin; body short and deep, greatly compressed. 
Sternoptychida. 
GG. Vertebral spines not exserted in front of dorsal. 
H. Pseudobranchite present. 
I. Premaxillaries forming entire margin of upper jaw; body scaly; opercular apparatus complete. 
J. Form elongate, the snout pointed, barracuda-like; photophores very small Paralepidida. 
JJ. Form oblong, the snout not much produced; photophores conspicuous Myctophida. 
II. Premaxillaries not forming the whole margin of upper jaw, the maxillary entering into it; body naked; opercular 
apparatus incomplete Maurolocida. 
HH. Pseudobranchise absent; mouth large, with canine teeth; scales deciduous or wanting Chauliodontida. 
AA. Back without adipose fin. 
B. Dorsal fin single, made up of rays, and not preceded by a series of free spines or followed by finlets. 
C. Tail evidently strongly heterocercal; scales ganoid; no -gular plate; dorsal fin short Lepisosteida. 
CC. Tail not evidently heterocercal. 
D. Tail tapering to a point, without caudal fin; anal fin very long, of about 200 rays; body scaly Halosaurida. 
DD. Tail not tapering to a point; caudal fin developed. 
E. Body naked. 
F. Throat with a long barbel; no caudal filament; mouth large. 
G. Barbel free at tip Stomiatida. 
GG. Barbel connecting throat with symphysis of lower jaw Malacosteid.i.. 
FF. Throat without barbel. 
H. Caudal fin with a long filament; body elongate; mouth very small Fistulariida. 
HH. Caudal fin without filament. Pectorals present Rondeletiida. 
EE. Body scaly. 
I. Head with a large divided luminous plate in place of eyes Ipnopida. 
II. Head with normally developed eyes. 
J. Anal fin with many spines; mouth toothless, sucker-like Lipogenyida. 
JJ. Anal fin without distinct spines. 
K. Pectoral fins inserted high, near axis of body; lower pharyngeals united; lateral line along side of belly. 
L. Jaws each with long sharp teeth mixed with smaller ones Esoctda. 
LL. Jaws with small equal, conic or tricuspid teeth. 
M. Lower jaw more or less produced; teeth tricuspid Hemiramphid.e. 
MM. Lower jaw a little produced; teeth conic; pectoral elongate, forming an organ of flight , Exoccetida. 
KK. Pectoral fins inserted below axis of body; lower pharyngeals separate. 
N. Phosphorescent spots present; teeth unequal Chauliodontida. 
NN. Phosphorescent spots none. . 
O. Head scaly, more or less. 
P. Maxillaries connate with premaxillaries; jaws long Synodontida. 
PP. Maxillaries distinct; upper jaw protractile, its margin formed by premaxillaries alone; no lateral line . Pocciliida. 
OO. Head naked. 
Q. Dorsal fin inserted more or less before anal (rarely slightly behind it); shore fishes or river fishes, usually silvery 
in coloration and with skeleton firm; air-bladder well developed. 
R. Gular plate present, between branches of lower jaw; mouth large; teeth present, all pointed; axillary scales and 
sheaths large Elopida. 
RR. Gular plate none. 
S. Lateral line well developed; mouth small, horizontal; posterior part of tongue and roof of mouth covered with 
coarse-paved teeth Aebulida. 
SS. Lateral line wanting; no gular plate. 
T. Mouth moderate, terminal, the maxillary of about 3 pieces; stomach not gizzard-like Clupeida. 
TT. Mouth subinferior, very large, below a tapering, pig-like snout; maxillary very long Engratjlidida. 
QQ. Dorsal fin posterior, opposite anal; deep-sea fishes, of loose organization; mostly blackish in color; mouth small, 
with small pointed teeth; air-bladder wanting Alepocephalida. 
1 The laneelets, sharks, and rays are not included in this key. 
