THE FISHES OF PORTO RICO. 
69 
Family IX. EEPTOCEPRALIDdi. The Conger Eels. 
This family includes those eels which are scaleless, and have the tongue largely free in front; body 
moderately elongate, end of tail surrounded by a fin; posterior nostril remote from upper lip and near 
front of eye, and pectoral fins well developed. All the species are plainly colored, grayish or dusky 
above, silvery below, and the dorsal edged with black. 
Genera 3, species about 15; in most warm seas, usually at moderate depths. Most of the species 
undergo a metamorphosis, the young being loosely organized and transparent, band-shaped, and with 
very small head. The body grows smaller with increased age, owing to compacting of the tissues. 
a. Vomerine teeth in bands, none of them canine-like; lips thick. 
b. Dorsal fin inserted at a point behind base of pectoral, but nearer pectoral than vent; head with inconspicuous 
mucus cavities; jaws with an outer series of close-set teeth, forming a cutting edge; tail about half longer than 
rest of body Leptocephalus, 10 
bb. Dorsal lin beginning over the gill-opening; bones of front of head with large muciferous cavities; mouth rather 
small; jaws with bands of small teeth, the outer not forming a cutting edge; tail from half to two-thirds of 
total length Congermurjbna 
aa. Vomerine teeth uniserial, some of them canine-like; maxillary teeth biserial; dorsal beginning above root of pec 
toral; cleft of mouth extending beyond middle of eye; tail very long and slender, about half longer than rest 
of body Uroconger 
Fig. 6. — Leptocephalus conger. 
Genus 10. LEPTOCEPHALUS (Gronow) Scopoli. 
Body formed as in Anguilla, skin scaleless. Head depressed above, anteriorly pointed. Lateral 
line present. Mouth wide, its cleft extending at least to below middle of eye. Teeth in outer series 
in each jaw equal and close-set, forming a cutting edge; no canines; band of vomerine teeth short. 
Tongue anteriorly free. Vertical fins well developed, confluent around tail; pectoral fins well devel- 
oped; dorsal beginning close behind pectorals. Gill-openings rather large, low. Eyes well developed; 
posterior nostril near eye, the anterior near tip of snout, with short tube. Lower jaw not projecting. 
Skeleton differing in numerous respects from that of Anguilla. Vertebrae about 56+100. 
This genus is found in most warm seas, and contains the well-known and widely distributed conger 
eel and three or four closely related species. The earliest generic name used for members of the group 
is Leptocephalus, based on a curious, elongate, transparent, band-like creature, with minute head and 
very small mouth, found in the waters of Europe, and known as Leptocephalus morrissi. This has been 
shown by Gill, Gunther, and Facciola to be the young and larval form of Leptocephalus conger. A 
number of the genera and species of the supposed family of Leptocephalidie have been described, but 
there is no doubt that all of them are larvae, some of eels, as Conger, Conger mursena, Ophisurus, and 
Neitastoma, others of Isospondylous fishes, as Albula, Elops, Alepocephalus, Stomias, etc. (See Gunther, 
Cat,., viii, 136. ) It is thought by Dr. Gunther that the Leptocephalid forms are probably “individuals 
arrested in the development at a very early period of their life, yet continuing to grow to a certain 
size, without corresponding development of their internal organs, and perishing without having attained 
the characters of the perfect animal.” The recent observations of Dr. Gilbert on the larvse of Albula, 
Elops, and Conger, however, seem to point to the conclusion that these curious forms are normal young, 
and that the individuals grow smaller in size for a time with increased age, owing to the increasing 
compactness of the tissues. 
a. Dorsal beginning nearly opposite tip of pectoral; head about 1.8 in trunk conger , 12 
aa. Dorsal fin beginning above middle of pectoral; head about 1.6 in trunk caudilimbatus 
