846 PROCEEDINGS OF THE NATIONAL MUSEUM vol.xxiii. 



4. HISTIOBRANCHUS Gill. 



Hisliulmoichtix (.iihu, Proc. IT. S. Nat. I\Iuf^., 1883, p. 255 {hifenidJis). 



I'hi.s g-eims i.s clo.se to the preceding, from which it i.s di.stingui.shed 

 by the more anterior iii.sertion of its dorsal. Two species have been 

 described, perhaps identical with each other, (iffriov^ sail, i. e., dor- 

 sal tin; fiftixyxioi^ gills; from the insertion of the dorsal.) 



6. HISTIOBRANCHUS BATHYBIUS (Giinther.) 



StjnapJutlmmchus hnthyhruK Gunthkk, Ann. and Mag. Nat. Hist., XX, 1877, p. 



445; and in Voy. Challenger, 1887, j). 254, pi. lxii, fig. 1), off Tokyo, North 



Pacific, Kerguelen Island. 

 Hisliohnmrhui^ bathyhhis Jordan and Evkkmanx, Fish. N. >I. America, I, 1896, 



p. 352, Bering Sea. 



Pectoral tin longer than snout; eye one-half or two-thirds of the 

 length of snout; head and tnudv i\ in tail; dorsal beginning above 

 or imnKHliately behind the pectoral, which is only one-third length of 

 head; scales quite rudimentar}', lanceolate, imbedded in the skin; 

 cheeks naked; dorsal and anal hns low, especialh" the former. Uni- 

 formly black. (Giinther.) Northern and western Pacilic in deep 

 water otif Tokyo, not obtained i)v us; one specimen taken in Bering 

 Sea in 1890. (ySrt'6't'g,,deep; (iio?, life.) 



Family IV. LEPTOCEPHALID^. 

 CONGER EP:L8. 



This family includes those eels which are scaleless, and have the 

 tongue largely free in front, the })ody moderately elongate, the end 

 of the tail surrounded by a fin, the ])osterior nostril remote from the 

 upper lip and near front of eye, and the pectoral tins well developed. 

 Lower jaw more or less included; teeth on sides forming a cutting 

 edge; lateral line well developed. All the species are plainly colored, 

 grayish or dusky above, silvery below. Species found in most warm 

 seas, usually at moderate depths. Most of the species undergo a 

 metamorphosis, the yoimg being loosely organized and transparent, 

 band-shaped, and with very small head. The body grows smaller with 

 increa.sed age, owing to the compacting of the tissues. The two genera 

 found in Japan are not well .separated and should perhaps be reunited. 



a. Insertion of dorsal over or behind middle of i)ectoral; tail notably longer tlian 

 rest of body ; mnciferous cavities of sknll small Leptocephahix. 5. 



aa. Insertion of tlorsal before nuddle of pectoral; snont and mouth smaller; skull 

 more cavernous. 

 /;. Teeth mostly pointed;' tail not half longer than rest of body < 'oiujir/his. 6. 



^ Teeth blunt or molar in Congermursena (type Imhenatn). 



