. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 424 PAKENTAL CAKE AMONG FRESH-WATEK FISHES. THE BICHIRS. The family of Polypterids or Bichirs is peculiarly interesting, as, to a greater extent than any other recent group, it is intermediate between fishes and amj^hibians—that is, betAveen vertebrates having fins and those with legs. The body is more or less elongated or sub- cylindrical and covered with ol)lique rows of enameled rhombic scales; the head is snakelike and protected by bony
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 424 PAKENTAL CAKE AMONG FRESH-WATEK FISHES. THE BICHIRS. The family of Polypterids or Bichirs is peculiarly interesting, as, to a greater extent than any other recent group, it is intermediate between fishes and amj^hibians—that is, betAveen vertebrates having fins and those with legs. The body is more or less elongated or sub- cylindrical and covered with ol)lique rows of enameled rhombic scales; the head is snakelike and protected by bony plates; the caudal fin rounded and continuous upward and forward with the dorsal fin; the dorjs^Ji furniture is especially remarkable; there are along most of the length of the back a row of spines (very different from the spines of other fishes) Avith whose hinder surfaces generally several raylike appendages articulate and a membrane is developed, thus resembling separate finlets. The anal is small and almost continuous with the caudal fin, and the ventrals are also far back; the pectorals are rounded and most prominent below the middle of the hinder margin. The family has two very distinct genera—PolypteriiH and Cala- michthys. Of the former one or more of 10 species are found every-. PoUjptcnis hicliir. After Geoffrey Saint-Ililaire. where in tropical Africa; of the latter only one—a very elongated, eel-like form without ventral fins—occurs in a few rivers of Avestern Africa. The species of Polypterus are so much alike that they have been supposed by some to be variants of one species, but they are really Avell distinguished by differences in the number of dorsal spines (ranging from 5 to 18), size of scales, size of eyes, and other charac- ters. The oldest knoAvn species (it Avas knoAvn to the ancient Egyp- tians, but Avas first described by Geoffroy Saint-Hilaire in 1809) is at one extreme Avith 15 to 18 spines, and one, described by W. O. Ayers, of Boston, in 18
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