APODAL FISHES OF AMERICA AND EUROPE. 
583 
But the mutual relations and value of these groups can only be ascer- 
tained by a thorough study of the anatomy of the various genera, and 
until such studies are made these groups may stand as separate fami- 
lies. As Cope has observed, there is no more propriety in putting all 
Eels in one family because of their agreement in form than there would 
be in putting in a similar family all fishes which agree in being “ fish- 
shaped . 77 
The following analytical key gives the salient characters of the fami- 
lies included in the present paper : 
ANALYSIS OF THE FAMILIES OF APODES FOUND IN EUROPE AND AMERICA. 
A. Opercular bones present and at least one osseous branchial arch; pharyngeal jaws 
developed; ceratohyal present. (ApodeS.) 
a. * Gill-openings small, roundish, leading to restricted interbranchial slits; tongue 
wanting; pectoral fins (typically) wanting; opercles feebly 
developed; fourth gill arch modified, strengthened and sup- 
porting pharyngeal jaws. (Suborder Colocephali.) 
b. Scapular arch obsolete or represented by cartilage ; heart not far back ; pec- 
torals wanting ; (skin thick ; coloration often variegated.) 
MuR^ENIDjE, I. 
aa. Gill-openings larger, leading to larger interbranchial slits; tongue present; 
opercles and branchial bones better developed; scapular 
arch present. (Suborder Enchelycepiiali.) 
c. Scales wholly wanting; eggs (so far as known) of moderate size, much as 
in ordinary fishes. 
d. Tip of tail without rays, projecting beyond the dorsal and anal fins (not 
filiform) ; posterior nostril on the edge of the upper lip ; an- 
terior nostril near tip of snout, usually in a small tube; 
tongue usually adnate to the floor of the mouth. (Colora- 
tion frequently variegated.) Ophisurid^e, II. 
dd. Tip of tail with a more or less distinct fin, the dorsal and anal fins con- 
fluent around it; the tail sometimes ending in a long fila- 
ment. (Coloration almost always plain, brownish, blackish, 
or silvery, the fins often black-margined.) 
e. Posterior nostril close to the edge of the upper lip ; tongue more or less 
fully adnate to the floor of the mouth ; teeth subequal. 
Echelid,e, III. 
ee. Posterior nostril without tube, situated entirely above the upper lip. 
/. Tongue narrow, adnate to the floor of the month or only the tip 
slightly free ; vomerine teeth well developed, sometimes en- 
larged. 
g. Jaws not attenuate and recurved at tip ; gill-openings well sepa- 
rated ; anterior nostrils remote from eye. 
h. Pectoral fius well developed; skin thick; skeleton firm; snout 
moderate ; tail not ending in a filiform tip. 
MUR.ENESOCID.E, IV. 
Jih. Pectoral fins wholly wanting; snout and jaws much produced, 
the upper longer; jaws straight; skin thin, the skeleton 
weak ; tail ending in a filiform tip ; gill-openings small, sub- 
inferior ; teeth sharp, subequal, recurved ; a long series on the 
vomer ; deep-sea eels, soft in body, black in color. 
Nettastomidje, V. 
*This diagnosis is chiefly taken ffom Gill, Proc. IT. S. Nat. Mus., 1890, 166. 
