544 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 
There can be little question as to the naturalness of this group of 
species, although they have been described as members of the follow- 
ing diverse genera: Macrourus, Optonurus, Malacocephalus, Cory- 
phaenoides, Chalinura. 
KEY TO THE SPECIES OF VENTRIFOSSA. 
a’. A scaleless ventral fossa, not pearly, nor lens-like, situated between the 
ventral fins, of variable size, and usually separated by a more or less ¢om- 
plete scaly bridge from the peritroct; mouth little oblique; spinules on 
seales arranged in quineunx order. 
b*. Teeth of lower jaw in two series; canines of upper jaw arrow-shaped ; 
denticulations of dorsal spine obsolescent; scales with a few short 
spinules; orbit about 3 in head__________ (ATHERODUS, new subgenus. ) 
atherodon.* 
b?. Teeth of lower jaw in three or more series, forming a narrow band; denti- 
culations of dorsal spine numerous and sharp; scales beset with numer- 
OUS "Spin GSS Se ee Se eae eee Bs (Subgenus VENTRIFOSSA. ) 
c. Sides of head and body brownish, with little or no silvery ; scales small. 
ad’. Preopercle not produced backward at its angle; outer ventral ray 
filamentous; upper jaw shorter, its length 22 in head__macronemus. 
d’. Preopercle produced backward at its angle; outer ventral ray not 
filamentous ; upper jaw longer, its length 24 in head_______ misakia. 
Sides of head and body bright silvery ; scales of moderate size. 
e’*. An area of enlarged spineless scales behind first dorsal; eye about 4 
in head; 6 rows of scales from last ray of first dorsal to lateral 
line; first dorsal black, with a white base and tip (Alcock). 
petersonii. 
e’. No area of enlarged or spineless scales behind first dorsal fin; orbit 
3.5 in head, or larger. - 
f. Preopercular ridge not sharply produced backward. 
7. First dorsal fin with a distinct black spot; ventrals blackish. 
h*. Ventral fossa very small, as in garmani, its front being behind 
the bases of the outer ventral rays; barbel about % as long 
Ce 
as: the ;Snout. ° 23: eee ee ee eee nigrodorsalis. 
h*. Ventral fossa of moderate size, its front being in line with the 
OWwler Venta ray See ee ee ee eee ctenomelas. | 
@. First dorsal fin without a distinct black spot; ventrals paler; 
ventral fossa small; barbel longer than the snout, being con- 
tained 2.8 to 4.0 times in the head. 
. 7 to 9 series of scales separating the front of second dorsal 
from lateral line row; interorbital width less (0.20 to 0.28, 
usually 0.21 or 0.22 of length to anus_____-__--____ divergens. 
?. 6 series of scales above lateral line; interorbital wider (0.22 to 
0.29, usually 0.25 to 0.27 of length to anus) ________ garmant. 
f. Preopercular ridge sharply produced backward at its angle. 
occidentalis. 
a. A lens-like organ immediately before anus, and another between the ventrals, 
much as in I/ymenocephalus; mouth little oblique; spinules on scales 
arranged along parallel series__-+_-—-_=3-- LUCIGADELLA, new subgenus. ) 
nigromarginata, 
1This species approaches the genus Malacocephalus most closely. 
