112 Barriers to Dispersion of River Fishes 
species now found being evidently an overflow from the Snake 
River when in late glacial times it drained Lake Bonneville. 
This postglacial lake once filled the present basin of the Great 
Salt Lake and Utah Lake, its outlet flowing northwest from 
Ogden into Snake River. The same fishes are now found in 
the upper Snake River and the basins of: Utah Lake and of 
Sevier Lake. In the same fashion Lake Lahontan once occu- 
pied the basin of Nevada, the Humboldt and Carson sinks, with 
Pyramid Lake. Its drainage fell also into the Snake River, 
and its former limits are shown in the present range of species. 
These have almost nothing in common with the group of species 
inhabiting the former drainage of Lake Bonneville. Another 
postglacial body of water, Lake Idaho, once united the lakes 
of Southeastern Oregon. The fauna of Lake Idaho, and of the 
lakes Malheur, Warner, Goose, etc., which have replaced it, is 
also isolated and distinctive. The number of species now known 
from this region of these ancient lobes is about 125. This list is 
composed almost entirely of a few genera of suckers,* minnows, Tt 
and trout.t None of the catfishes, perch, darters, or sunfishes, 
moon-eyes, pike, killifishes, and none of the ordinary Eastern 
types of minnows § have passed the barrier of the Rocky Moun- 
tains. 
West of the Sierra Nevada the fauna is still more scanty, 
only about seventy species being enumerated. This fauna, ex- 
cept for certain immigrants || from the sea, is of the same general 
character as that of the Great Basin, though most of the species 
are different. This latter fact would indicate a considerable 
change, or “evolution,” since the contents of the two faune 
were last mingled. There is a considerable difference between 
the fauna of the Columbia and that of the Sacramento. The 
species which these two basins have in common are chiefly 
those which at times pass out into the sea. The rivers of Alaska 
contain but few species, barely a dozen in all, most of these 
being found also in Siberia and Kamchatka. In the scanti- 
* Catostomus, Pantosteus, Chasmistes. 
{ Gila, Ptychocheilus, etc. 
t Salmo clarkii and its varieties. 
§ Genera Notropis, Chrosomus, etc. 
| As the fresh-water surf-fish (Hysterocarpus traski) and the species of 
salmon. 
