DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 137 



* No scales. Jaws even. Teeth present or absent on vomer Leptocephalid^ 



" Scales present, miunte. Lower jaw projecting. Vomerine teeth [Anguillid.e] 



b. Gill openings horizontal, inferior. Scales present. Lips obsolete, or nearly so. 



* Snout obtuse. Jaws powerful. Teeth in jaws blunt, uniserial, with none on vomer. 



SlMEXCnKI.YID.4; 



** Snout conical. Jaws uioiler.ately strong. Teeth sharp, in bands in jaws :ind on vomer. 



iLYOPlIIUiE 



2. Gill openings inferior and coulluent. 

 a. Head conical ; tongue small. 



* Posterior nostrils close to eye. Branchiostegals shortened SYNAPHoRRANC'HiDiE 



B. Pectoral fms absent. 



1. Gill openings distinct, lateral. Scales wanting. Moutli oblique, with projecting lower jaw 

 and short obtuse snout. 



a. Body and tail very elongate. Teeth in bands in jaws and on vomer Heterocongrid.*; 



II. Tongue narrow, not free. No scales. 

 Gill openings rather wide. 



A. Pectorals stroug. 



1. End of tail normally surrounded by vertical fins. Sifeleton firm. SIvin thick. 



a. Jaws moderate. Vomer dentigerous Mur.knesocid^ 



* Dorsal and anal well developed Muranexochia' 



** Vertical fins scarcely developed except on tail {^Slilbincina:'] 



B. Pectorals moderate, weak, or absent. 



1. End of tail more or less free. 



a. Posterior nostrils iu lip (u- near it; anterior one sometimes tnl)ular OpniCHTHYiD.E 



* Fins present, at least on back Ophichthyinm 



** Fins absent Sphagebranchinm 



2. Tip of tail more or less surrounded. 



a. Dorsal well developed ; pectorals sometimes united Myrince 



Gill openings small, subinferior. 

 A. Pectorals lacking. 



1. End of tail prolonged in a filament. Skin thin. Skeleton weak, 

 a. Jaws straight, slender, the upper longest. 



* Teeth sharp, recurved. Vomer with a long series Nettastomid^ 



Gill openings convergent forward, separate or confluent. 



A. Pectorals present (in American genera). 



1. Jaws very long, recurved at tip Nemichthyid^ 



Family LEPTOCEPHALIDvE. 



Cnngeridfr, Kaup, Cat. Apodal Fish, in Brit. Mus.,1856, 108. 

 Cuiigriila; Jordan & Davis, Hep. U. S. F. C, 1888 (1801), 658. 

 Leptocephalidw, GiLi,, MS. 



Body terete, moderately elongate, with the tip of the tail included between the connate 

 vertical iins. Scales absent. Head large, with stroug equal jaws. Tongue broad, its ante- 

 rior nortion comparatively free. Opercular and branchial bones well developed. Vomerine 

 teeth moderate. Anterior nostril remote from eye. Posterior nostril, near the eye, tube- 

 less, not touching the lip. Pectorals, well developed. 



This family includes those eels which are scalclcss and have the tongue largely free 

 in front, tlie Ijody nuxlcratcly elongate, the end of the tail surrounded by a fin, the posterior 

 uostril remote from the upper lip and near front of eye, and the pectoral flus well developed. 

 All the s^iecies ar(> plainly colored, grayish or dusky above, silvery below, and have the 

 dorsal edged with black. 



KEY TO THE GENERA OF LEPTOCEPHALID.E. 



I. Vomerine teeth in bands, uniform iu size; lips thick. 



A. Dorsal origin lichind root of pectoral. 



1. Jaws with outer knife-like row of closely set teeth. Head with inconspicucius nuicous 

 cavities, 

 a. Tail considerably longer than body [LEPT()CEPnAHS=CONGER3 



B. Dorsal origin over the gill opening. 



1. Jaws with bands of sni.all teeth, the outer not forming a euttingedge. Hones of front of head 

 with largo nuiciferous cavities. 

 a. Tail one-half to two-thirds of total. Mouth rather small CONGERMUR^NA 



