[103] There are three species of darters (Cottogaster copelandi Jordan, Hadropterus evides Jordan and Copeland, Hadropterus scierus Swain) which are now known only from the Ozark region or beyond and from the uplands of Indiana, not yet having been found at any point between Indiana and Missouri. These constitute perhaps isolated colonies, now separated from the parent stock in Arkansas by the prairie districts of Illinois, a region at present uninhabitable for these fishes. But the non-occurrence of these species over the intervening areas needs confirmation, as do most similar cases of anomalous distribution.
[104] Thus, Dorosoma cepedianum Le Sueur and Pomolobus chrysochloris Rafinesque have found their way into Lake Michigan through canals.
[105] Oncorhynchus tschawytscha Walbaum.
[106] Oncorhynchus nerka Walbaum.
[107] "In this isolated region of North America, in this zoological island of New England, as we may call it, we find neither Lepidosteus, nor Amia, nor Polyodon, nor Amblodon (Aplodinotus), nor Grystes (Micropterus), nor Centrarchus, nor Pomoxis, nor Ambloplites, nor Calliurus (Chænobryttus), nor Carpiodes, nor Hyodon, nor indeed any of the characteristic forms of North American fishes so common everywhere else, with the exception of two Pomotis (Lepomis), one Boleosoma, and a few Catostomus."—Agassiz, Amer. Journ. Sci. Arts, 1854.
[108] Catostomus, Pantosteus, Chasmistes.
[109] Gila, Ptychocheilus, etc.
[110] Salmo clarkii and its varieties.
[111] Genera Notropis, Chrosomus, etc.
[112] As the fresh-water surf-fish (Hysterocarpus traski) and the species of salmon.