664 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
brane and supported by fragile plates and crests. Dentition weak, composed of minute villiform teeth 
in very narrow bands, the latter tapering laterally, but comprising usually at least 2 series of teeth to 
their ends; with considerable magnification, the teeth are seen to be dilated and flattened below the 
tip, distinctly lance-shaped; mouth terminal, very slightly overpassed by the prominent median point 
of snout; maxillary falling a little short of a point opposite hinder edge of orbit; horizontal and verti- 
cal diameters of orbit equal, 0.4 the length of head; posterior margin of preopercle extending obliquely 
upward and forward; a small opaque lens-like body, resembling a photophore, occupies the middle 
of the breast, and is connected by a raised black line below the peritoneum with a similar body 
immediately before the vent. 
Scales very thin and deciduous, many of them smooth and unarmed, as described in the type. 
Others may have a few (1 to 10) short, scattered spines, wholly without definite arrangement. 
In specimens taken July 21 at station 4088, the eggs have nearly reached maturity, the ovaries 
exceeding in size all other contents of the abdominal cavity. They are so uniform in their develop- 
ment in some twenty specimens examined as to suggest a definite breeding season in this species. The 
ovaries are completely united in their posterior third, but diverge anteriorly. The stomach contains 
largely digested remains of small Crustacea. There are but few (about 12) pyloric caeca. 
The peculiar and highly developed color-pattern of the gular membrane, sides of throat and area 
on outer side of base of ventrals has been pointed out in the original description of the species. In 
addition to the conspicuous dark line along middle of side of tail, there is a band of dark specks above 
this line, separated from the base of anterior part of dorsal fin by a colorless streak; below the middle 
of tail is a wide colorless band, then a narrow streak composed of black specks, separated from base of 
anal by a narrow colorless streak; posteriorly, all the dark streaks blend, the terminal portion of tail 
being distinctly blackish; tip of snout marked by a narrow black transverse line, often interrupted; 
lining of mouth largely colorless; the bands of teeth black; a transverse black arch overlying palatines 
and head of vomer, and a black streak on floor of mouth in front of tip of tongue; linings of shoulder 
girdle and branchiostegals black. 
There can be no doubt of the close relationship between the 2 Hawaiian species of Hymenocephalus 
and the Atlantic H. italicus Giglioli, the type of the genus. They agree not only as regards the smooth 
dorsal spine and the large terminal mouth with narrow bands of minute equal teeth, but in the 
presence of the peculiar coloration above base of ventral fin, and the small tubercle on the median line 
of breast. In H. italicus, the last-mentioned characters are described by Collett (Poissons de l’Hiron- 
delle, 1896, p. 87), in the following terms: “ Imnnkliaternent au-dessus des ventrales, la peau du ventre 
est legerement rayee, du moins chez les jeunes individus; ces raies descendent vers la ligne ventrale. 
En avant des ventrales, on remarque sur la ligne mediane du corps une petite protuberance mamillaire 
ronde. ’ ’ The 3 species agree also in their very small size, the great development of the cephalic mucous 
cavities, and the extremely caducous scales, which show a strong tendency to loss of spines. Compared 
with H. italicus, the Hawaiian species are signalized by almost total loss of the mandibular barbel, and 
by increase in number of ventral rays. Other species referred to Hymenocephalus a seem not to share 
the common characters above noted, and may with advantage, perhaps, be removed from the group. 
Specimens were obtained at the following stations: Nos. 3865, Pailolo Channel, 256 to 283 fathoms; 
3883, Pailolo Channel, 277 to 284 fathoms; 3884, Pailolo Channel, 284 to 290 fathoms; 3898, Pailolo 
Channel, 258 to 284 fathoms; 3907, off the south coast of Oahu, 304 to 315 fathoms; 3908, off the south 
coast of Oahu, 304 to 308 fathoms; 3909, off the south coast of Oahu) 308 to 322 fathoms; 3910, off the 
south coast of Oahu, 311 to 337 fathoms; 3911, off the south coast of Oahu, 334 to 337 fathoms; 3912, 
off the south coast of Oahu, 310 to 334 fathoms; 3914, off the south coast of Oahu, 289 to 292 fathoms; 
3916, off the south coast of Oahu, 299 to 330 fathoms; 3917, off the south coast of Oahu, 294 to 330 
fathoms; 3918, off the south coast of Oahu, 257 to 294 fathoms; 3925, off the south coast of Oahu, 299 
to 323 fathoms; 4021, vicinity of Kauai, 286 to 399 fathoms; 4025, vicinity of Kauai, 275 to 368 fathoms; 
4085, off the north coast of Maui, 267 to 283 fathoms; 4086, off the north coast of Maui, 283 to 308 
fathoms; 4087, Pailolo Channel, 306 to 308 fathoms; 4088, Pailolo Channel, 297 to 306 fathoms; 4089, 
Pailolo Channel, 297 to 304 fathoms; 4090, Pailolo Channel, 304 to 308 fathoms; 4091, Pailolo Channel, 
306 to 308 fathoms; 4105, Pailolo Channel, 314 to 335 fathoms; 4106, Pailolo Channel, 335 to 350 
fathoms; 4140, Pailolo Channel, 339 to 437 fathoms. 
Hymenocephalus antrseus Gilbert & Cramer, Proe. U. S. Nat. Mus., XIX, 1897, 428, pi. xlvi, fig. 2. 
a The above was written before the description of H. striatissimus, H. papyraceus, and H. lelhonemus from Japan (see 
Jordan & Gilbert, Bull. U. S. F. C. for 1902, pp. 612-616), all of which possess the above-mentioned characters of the genus. 
