1877.] On the Distribution of Fresh- Water Fishes. O Gee 
represented by Hupomotis pallidus. In the West, Noturus gyri- 
nus by Noturus sialis, Noturus insignis by Noturus exilis, Umbra 
pygmea by Umbra limi. 
XV. Other species under similar circumstances have no such 
“ representatives.” The case of Luvilus cornutus will again 
illustrate. 
XVI. Certain species have been known to extend their geo- 
graphical range since the opening of the canals. Such aré*more 
especially migratory species of probably marine origin, as, for 
example, Dorysoma heterura, Pomolobus chrysochloris, and An- 
guilla vulgaris, now abundant in Lake Erie and Lake Michigan, 
but formerly unknown there. The range of certain Percide 
and Centrarchide has been extended by the same means. 
XVII. Rivers flowing parallel into the same larger stream 
have more in common than rivers having their mouths nearer to- 
gether but flowing from opposite directions. The Wabash and 
Miami have more in conimon than either has with the Kentucky. 
XVIII. The characteristically American forms of fishes are, 
generally speaking, rare or absent in the waters of New England 
and of the Pacific slope. This fact has been apprehended by 
Professor Agassiz, who called New England “a zodlogical 
island.” 
About one hundred and five genera of fresh-water fishes inhabit 
the waters of the United States, east of the Mississippi River. 
Of these, the following seventy-seven do not occur in New Eng- 
land (exclusive of Lake Champlain and tributaries of the St. 
Lawrence) : — 
Potamocottus,  Stizostethium,  Typhlichthys, Gila, 
Cottopsis, Micropterus, Chologaster, Nocomis, 
- Triglopsis, Ambloplites, Astyanax, Ericymba, 
Ammocry pta, Acantharchus, Percopsis, Exoglossum, 
Pleurolepis,  Chanobryttus, Thymallus, Lagochila, 
ercina, Apomotis, Hyodon, Placopharynx, 
Alvordius, Xenotis, Campostoma, Myxostoma, 
Ericosma, Xystroplites, Hybognathus, Cycleptus, 
Hadropterus, Mesogonistius, Pimephales, arpiodes, 
toma, cai Hyborhynchus, Ichthyobus, 
ypta, Copelan Hybopsis, Bubalichthys, 
Ulocentra (Jor. etara Lythrurus, Ichthælurus, 
MSS., Pomoxys, Cyprinella, Pelodichthys, 
Diplesium, Haploidonotus, Erogalia (Jor. Noturus, 
Ninostoma;  Aphododerus, ::: MSS), ‘Amin, 
