[77] _Aphredoderus sayanus_ Gilliams. [78] _Micropterus salmoides_ Lacépède. [79] _Ictalurus punctatus_ Rafinesque. [80] _Hiodon tergisus_ Le Sueur. [81] _Lepisosteus osseus_ Linnæus. [82] _Ictiobus bubalus_, _cyprinella_, etc. [83] _Aplodinotus grunniens_ Rafinesque. [84] _Micropterus dolomieu_ Lacépède. [85] _Coregonus clupeiformis_, _Argyrosomus artedi_, etc. [86] _Cristivomer namaycush_ Walbaum. [87] _Salmo salar_ Linnæus. [88] _Acipenser sturio_ and other species. [89] _Alosa sapidissima_ Wilson. [90] _Roccus lineatus_ Bloch. [91] _Anguilla chrysypa_ Raf. [92] Thus the chub-sucker (_Erimyzon sucetta_) in some of its varieties ranges everywhere from Maine to Dakota, Florida, and Texas; while a number of other species are scarcely less widely distributed. [93] Check List of the Fishes of the Fresh Waters of North America, by David S. Jordan and Herbert E. Copeland. Bulletin of the Buffalo Society of Natural History, 1876, pp. 133-164. [94] A Catalogue of the Fishes of the Fresh Waters of North America. Bulletin of the United States Geological Survey, 1878, pp. 407-442. [95] A Catalogue of the Fishes Known to Inhabit the Waters of North America North of the Tropic of Cancer. Annual Report of the Commissioner of Fish and Fisheries for 1884 and 1885. [96] Check List of the Fishes of North and Middle America. Report of the U. S. Commissioner of Fisheries for 1895. [97] _Ictalurus punctatus_ Rafinesque. [98] _Siluridæ._ [99] _Ameiurus nebulosus._ CHAPTER XVII BARRIERS TO DISPERSION OF RIVER FISHES =The Process of Natural Selection.=--We can say, in general, that in all waters not absolutely uninhabitable there are fishes. The processes of natural selection have given to each kind of river or lake species of fishes adapted to the conditions of life which obtain there. There is no condition of water, of bottom, of depth, of speed of current, but finds some species with characters adjusted to it. These adjustments are, for the most part, of long standing; and the fauna of any single stream has as a rule been produced by immigration from other regions or from other streams. Each species has an ascertainable range of distribution, and within this range we may be reasonably certain to find it in any suitable waters. [Illustration: FIG. 189.--Slippery-dick or Doncella, _Halichoeres bivittatus_ Bloch, a fish of the coral reefs, Key West. Family _Labridæ_.]