58 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
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IV. — Ventral Fins 
AV holly Wanting. 
Premaxillary and maxillary wanting or grown fast to palatines; body greatly elongate, eel-shaped., gib-openings 
restricted to the sides; scales minute or wanting; scapular arch not attached to the skull Eels. 
Gill-openings well developed, leading to large interbranchial slits; tongue present; opercles and oranchial bones 
well developed; scapular arch present. 
Skin covered with rudimentary embedded scales, usually linear in form, arranged in smail groups, and placed 
obliquely at right angles to those of the neighboring groups; pectorals and vertical fins well developed, the 
latter confluent about the tail; lateral line present; posterior nostril in front of eyes; tongue with its margins 
free Anguii.lip.-k. 
Scales wholly wanting; eggs (so far as known) of moderate size, much as in ordinary fishes. 
Tip of tail with a more or less distinct fin, dorsal and anal fins confluent around it; tail sometimes ending in a 
long filament; coloration almost always plain, brownish, blackish, or silvery, the fins often black-margined. 
Posterior nostril without tube, situated entirely above the upper lip. 
Tongue broad, largely free anteriorly and on sides; vomerine teeth moderate. 
Pectoral fins well developed; body not excessively elongate; lower jaw not projecting; anterior nostril remote 
from eye Eeptocephaijda;. 
Tongue narrow, adnate to the floor of the mouth or only the tip slightly free; vomerine teeth well developed, 
sometimes enlarged. 
Jaws not attenuate and recurved at tip; gill-openings well separated; anterior nostril remote from eye. 
Pectoral fin small or wanting Moringuidje. 
Pectoral fin well developed, skin thick; skeleton firm; snout moderate; tail not ending in a filiform tip. 
Murasnesocida?. 
Jaws long and slender, tapering to a point, recurved at tip; nostrils large, both pairs close in front of eye; gill- 
openings convergent forward, separate or confluent; pectorals and vertic 1 fins well developed; membranes 
of fins thin, not enveloping the rays; skeleton well developed. Deep-sea eels Nemichthyid.e. 
Posterior nostril close to the edge of the upper lip; tongue more or less fully adnate tc the floor of the mouth: 
teeth subequal Myrid.e. 
Tip of tail without rays, projecting beyond the dorsal and anal fins (not filiform); posterior nostril on the edge of 
the upper lip; anterior nostril near tip of snout, usually in a small tube; tongue usually adnate to the floor of 
the mouth; coloration frequently variegated Ophichthyim 
Gill-openings small, roundish, leading to restricted interbranchial slits; tongue wanting; pectoral fins (typically) 
wanting; opercles feebly developed; fourth gill-arch modified, strengthened, and supporting pharyngeal jaws. 
Mur.enid*. 
Premaxillary and maxillary present, often immovably united to rest of cranium. 
Gill-openings united in a single slit below throat; no pectoral fins; body eel-shaped Symbranchidie. 
Gill-openings not united in a longitudinal slit. 
Body eel-shaped, ending in a long filament, longer than rest of body; no anal or caudal fin Stylebhorid.e. 
Body not truly eel-shaped. 
Gill-membranes broadly united to the isthmus, restricting the gill-openings to the sides. 
Snout tubular, bearing the short, toothless mouth at the end; body mailed Syngnathida:. 
Snout not tubular. 
Dorsal fin single, of spines or undivided rays only Blenniida:. 
Dorsal fins 2, the anterior of spines, the posterior of soft rays; body short and deep. 
Spinous dorsal of 2 or 3 spines; scales rather large, rough or bony Balistida?. 
Spinous dorsal of 1 or 2 spines; scales minute, rough, forming a velvety covering Monacanthidie. 
Dorsal fin continuous, of soft rays only. 
Teeth in each jaw confluent into 1. 
Body compressed, rough Moliiwe. 
Body not compressed, spinous Diodontidae. 
Teeth in each jaw confluent into 2. 
Back broadly rounded Tetraodontida?. 
Back with a sharp median ridge C anthigasteridas. 
Teeth separate; body enveloped in a bony box Ostraciid.-e. 
Gill-membranes free from the isthmus. 
Vent at the throat; vertical fins confluent; body elongate, almost eel-shaped Fierasferida;. 
Vent posterior, not at the throat. 
Caudal fin wanting; body naked, greatly elongate Trichiurida?. 
Caudal fin present. 
Upper jaw prolonged into a sword; size very large Xiphtidaj. 
Upper jaw not prolonged into a sword. 
Belly with a series of bony scutes along its edge; body much compressed „ Clitpeid.e. 
Belly not armed with scutes. 
Body ovate, much compressed. 
Scales small, cycloid, silvery Stromateid.e. 
Scales wanting; caudal peduncle very slender Icosteida:. 
Body oblong or elongate, much longer than deep; gill-membranes broadly united; teeth present; dorsal fin of 
spines only, or the posterior half of soft rays, the anterior of spines _ Blenniidas. 
