JAPANESE FISHES. 
615 
98. Hymenocephalus leth.onem.us Jordan & Gilbert, new species. 
Type 142 mm. long, from station 3697, in Sagami Bay, Japan, depth 120 to 265 fathoms; No. 50936, 
U. S. Nat. Mus. Closely allied to II antrxus and II. striatulus from vicinity of the Hawaiian Islands, 
but well distinguished from other species by proportions and number of ventral rays. First dorsal ii, 
10 or ii, 11; ventrals 11. Plead 5.4 in total length; depth 8. Branchiostegals 7. 
Body very slender, tapering to a very long whip-like tail. Head subquadrate in cross section, 
interorbital area nearly flat, sides of head vertical; ridges on top and sides of head thin and papery, 
the large mucous canals roofed over by delicate transparent membrane; orbital rim projects above and 
behind as a thin membrane-like expansion; median crest on snout and interorbital protrudes but little 
above general level; snout terminates anteriorly in a sharply projecting point, similar to that in II 
striatulus, but slenderer and a little longer, projecting axially beyond the mouth for a distance slightly 
less than half orbital diameter; interorbital width 3.33 times in head; longitudinal diameter of orbit, 
3; length of snout, 3.5; middle of length of head midway between hinder margin of orbit and pupil; 
posterior line of occiput midway between origin of dorsal fin and anterior edge of nasal fossa; mouth 
large, its width nearly equal to greatest width of head, the maxillary reaching vertical from hinder 
margin of orbit, its length 1.87 in that of head; teeth minute, of uniform size, in very narrow bands in 
each jaw, the bands interrupted mesially: no trace of mandibular barbel. 
Hymenocephalus Icthimemus Jordan & Gilbert, new species. 
Preopercle dilated to form a wide membranous expansion at its angle, the greatest width of 
which is two-fifths the diameter of orbit, the margin crenulate; above the angle the preopercular 
margin is straight and slightly oblique; opercle very thin and flexible and strengthened by two 
diverging ridges, the one directed downward and backward terminating in a sharp concealed spine; 
gill membranes united anteriorly, forming a wholly free fold across isthmus; vertical limb of outer 
gill arch wholly adnate, the horizontal limb free from the angle forward for a distance equaling 
one-tliird the length of head; inner series of gillrakers compressed, movable, their inner margins 
strongly spinous, 18 on horizontal limb of second arch; second dorsal spine slender and weak, entirely 
smooth, its tip sometimes a little produced beyond rays. The interval between the dorsals is 1.9 
times base of first. A vertical line from origin of anal intersects this interspace slightly in advance of 
its middle; the anus immediately precedes anal fin; outer ventral ray filamentous in the type reaching 
base of tenth anal ray, its length equaling that of head; pectorals slender, 1.83 in head. 
The scales are largely lost in our specimens; one from the middle of the breast is cycloid, 
unarmed; 3 or 4 above and behind insertion of pectoral fin bear a few weak spines, with difficulty to 
be detected. There were apparently 3 rows of scales between the middle of the sides and origin of 
second dorsal tin. 
