Sea Serpent, a marine animal, by many considered fabulous, said to inhabit chiefly the northern seas, especially about the coasts of Norway and New England. The idea of a sea serpent originated in northern Europe, and was at first clearly mythological. Though hundreds of witnesses aver that they have seen this animal, naturalists have failed to discover any certain traces of it. For an account of its visits to Norway the reader may consult Pontoppidan's "Natural History of Norway" (fol., London, 1755), and vol. viii. of the "Naturalist's Library" (Edinburgh, 1841); and for its occurrence on the American coasts, vols, ii., xi., xii., and xxviii. of the "American Journal of Science," the "Report of the Committee of the Linnaean Society of New England" (Boston, 1817), Sir Charles Lyell's "Second Visit to the United States" (London, 1849), and Gosse's "Romance of Natural History" (London, 1860-62). This animal is said to appear in calm weather, with a slender body from 60 to 100 ft. long, a broad snake-like head as large as that of a horse, large eyes, and a long and narrow neck, and of a general dark brown color; some describe it as having fins. It is seen swimming at the surface, with the head and neck elevated, progressing swiftly, apparently by a vertical undulating motion.

There does not seem to be any fish to which this animal can be referred. Many fossil types of marine animals have been transmitted, with or without interruption, from remote geological epochs to the present time; among these may be mentioned the Port Jackson shark (ces-tracion), and the gar pike (lepidosteus), which have come down to us without interruption, chimoera, percopsis of Lake Superior, and soft-shelled tortoises (trionychidoe), with more or less apparent disappearance. Several years ago it was suggested that the closest affinities of the sea serpent are with the marine lizards or enaliosaurians of the secondary age, and especially with the plesiosaurus. (See Ple-siosaurus.) On the above principle it is maintained that the enaliosaurians, found in the secondary, may have disappeared, actually or apparently, in the tertiary, to reappear at the present time. This is also the opinion of Agassiz, as given in the report of his lectures in Philadelphia in 1849, and reaffirmed in his "Geological Researches" (1871). Mr. Gosse has collected from various sources the arguments showing that the non-occurrence of dead animals is of little weight as disproving the existence of the sea serpent; its carcass would float only a short time, and the rock-bound coasts of Norway would be very unlikely to retain any fragment cast up by the waves; many whales are known to naturalists only from two or three specimens in as many centuries.

The zeuglodon, a mammalian type of the tertiary epoch, coming near to the cetaceans and in some respects to the seals, may present some claim to be the sea serpent. (See Zeuglodon.) The conclusion of the best naturalists is that the existence of the sea serpent is possibly a verity, and that it may prove to be some modified type of the secondary enaliosaurians, or possibly some form intermediate between them and the elongated cetaceans. - See "Proceedings of the Boston Society of Natural History," vol. xvi. (March, 1874).