The eel is an excellent food-fish, the flesh being tender and oily, of agreeable flavor, better than that of any of its relatives. Eels often reach a large size, old individuals of five or six feet in length being sometimes taken. =Species of Eels.=—The different species are very closely related. Not more than four or five of them are sharply defined, and these mostly in the South Seas and in the East Indies. The three abundant species of the north temperate zone, _Anguilla anguilla_ of Europe, _Anguilla chrisypa_ of the eastern United States, and _Anguilla japonica_ of Japan, are scarcely distinguishable. In color, size, form, and value as food they are all alike. Fossil species referred to the _Anguillidæ_ are known from the early Tertiary. _Anguilla leptoptera_ occurs in the Eocene of Monte Bolea, and _Anguilla elegans_ in the Miocene of Œningen in Baden. Other fossil eels seem to belong to the _Nettastomidæ_ and _Myridæ_. =Pug-nosed Eels.=—Allied to the true eel is the pug-nosed eel, _Simenchelys parasiticus_, constituting the family of _Simenchelyidæ_. This species is scaled like a true eel, has a short, blunt nose, and burrows its way into the bodies of halibut and other large fishes. It has been found in Newfoundland and Madeira. Another family possessing rudimentary scales is that of the _Synaphobranchidæ_, slender eels of the ocean depths, widely distributed. In these forms the gill-openings are confluent. _Synaphobranchus pinnatus_ is the best-known species. [Illustration: FIG. 103.—Pug-nosed Eel, _Simenchelys parasiticus_ Gill. Sable Island Bank. ] [Illustration: FIG. 104.—_Synaphobranchus pinnatus_ (Gronow). Le Have Bank. ] =Conger-eels.=—The _Leptocephalidæ_, or conger-eels, are very similar to the fresh-water eels, but are without scales and with a somewhat different mouth, the dorsal beginning nearer to the head. The principal genus is _Leptocephalus_, including the common conger-eel (_Leptocephalus conger_) of eastern America and Europe and numerous very similar species in the tropics of both continents. These fishes are strictly marine and, reaching the length of five or six feet, are much valued as food. The eggs are much larger than those of the eel and are produced in great numbers, so that the female almost bursts with their numbers. Dr. Hermes calculated that 3,300,000 were laid by one female in an aquarium. These eggs hatch out into transparent band-like larva, with very small heads formerly known as _Leptocephalus_, an ancient name which is now taken for the genus of congers, having been first used for the larva of the common conger-eel. The loose watery tissues of these "ghost-fishes" grow more and more compact and they are finally transformed into young congers. [Illustration: FIG. 105.—Conger-eel, _Leptocephalus conger_ (L.). Noank, Conn. ]