ICHTHYOPHAGI (Gr. for "fish-eaters"), the name given by ancient geographers to several coast-dwelling peoples in different parts of the world and ethnically unrelated. Nearchus mentions such a race as inhabiting the barren shores of the Mekran on the Arabian Sea; Pausanias locates them on the western coast of the Red Sea. Ptolemy speaks of fish-eaters in Ethiopia, and on the west coast of Africa; while Pliny relates the existence of such tribes on the islands in the Persian Gulf. Herodotus (book i. c. 200) mentions three tribes of the Babylonians who were solely fish-eaters, and in book iii. c. 19 refers to Ichthyophagi in Egypt. The existence of such tribes was confirmed by Sir Richard F. Burton (_El-Medinah_, p. 144). ICHTHYOSAURUS, a fish or porpoise-shaped marine reptile which characterized the Mesozoic period and became extinct immediately after the deposition of the Chalk. It was named _Ichthyosaurus_ (Gr. fish-lizard) by C. König in 1818 in allusion to its outward form, and is best known by nearly complete skeletons from the Lias of England and Germany. The large head is produced into a slender, pointed snout; and the jaws are provided with a row of conical teeth nearly uniform in size and deeply implanted in a continuous groove. The eye is enormous, and is surrounded by a ring of overlapping "sclerotic plates," which would serve to protect the eye-ball during diving. The vertebrae are very numerous, short and deeply biconcave, imparting great flexibility to the backbone as in fishes. The neck is so short and thick that it is practically absent. There are always two pairs of paddle-like limbs, the hinder pair never disappearing as in porpoises and other Cetacea, though often much reduced in size. A few specimens from the Upper Lias of Württemberg (in the museums of Stuttgart, Tübingen, Budapest and Chicago) exhibit remains of the skin, which is quite smooth and forms two triangular median fins, one in the middle of the back, the other at the end of the tail. The dorsal fin consists merely of skin without any internal skeleton, while the tail-fin is expanded in a vertical plane and has the lower lobe stiffened by the tapering end of the backbone, which is sharply bent downwards. Immature individuals are sometimes observable within the full-grown skeletons, suggesting that this reptile was viviparous. [Illustration: From British Museum _Guide to Fossil Reptiles and Fishes_, by permission of the Trustees. Skeleton of _Ichthyosaurus communis_, with outline of body and fins, from the Lower Lias of Lyme Regis, Dorset; original nearly four metres in length.]