236 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
FLATHEAD RIVER SYSTEM. 
The waters of the Flathead region from which collections were made by us were 
Swan and Flathead lakes and Flathead, Swan, and Coeur d’Alene rivers, and the 
Jocko at Ravalli. Those from the lakes only can be here discussed. 
Flathead Lalce . — Although this lake stands in some respects in decided contrast to 
Yellowstone Lake, these differences tend largely to neutralize each other. Flathead 
Lake is over 200 miles farther northward than Yellowstone, but the latter is 4,775 feet 
the higher above the level of the sea. These lakes lie on opposite continental slopes, 
their waters passing respectively into the Gulf of Mexico and the Pacific Ocean, but 
neither is more than a few miles from the relatively low continental divide, easily 
passable by most of the plant and animal forms likely to occur in such waters. Both 
lakes lie in the course of streams of considerable size, but these streams flow in 
opposite directions, the inlet of Flathead Lake coming southward from the British 
Possessions, and its outlet running first to the south and then to the west as Flathead 
River, a branch of the Columbia, while Yellowstone River, rising about 50 miles 
above the lake, runs northward more than a degree below it before swinging to the 
east to join the Missouri. Nevertheless, the headwaters of the two river systems inter- 
lace almost inextricably through interlocking mountain valleys along several hundred 
miles of the main Rocky Mountain range. Both lakes lie among mountains from 
whose rugged gulches the snow never wholly disappears, and both are bordered by 
forests broken by park-like openings on the lower slopes ; but the geological structure 
of the surrounding country and 'the chemical composition of the rocks which form 
their shores and beds differ widely for the two, and the forests, all pine and fir and 
other conifers around Yellowstone Lake, are largely deciduous trees about Flathead. 
The lakes are similar in size and are both deep enough to give a deep-water 
character to their interior fauna, but Flathead has much the more uniform shore-line 
and contains — if I may judge from the parts of it which we examined — a larger 
extent of shallow and weedy water. It is divided, in fact, by a chain of islands 
stretching across its lower third, into unlike parts ; the northern deep and clear, and the 
southern shallow, and easily stirred up to its clayey bottom by the winds. 
Finally, both lakes, like most of this region, are evidently far smaller now than 
they were in an earlier geological period. The extension of the old Flathead above 
the present lake is shown by the terraces marking its former shores, which may be 
traced, one above the other, for a considerable distance above the inlet; while Hayden 
Y alley, the deserted part of the Yellowstone Lake, lies below the lake along its pres- 
ent outlet. 
The Flathead is reported by steamboat men and residents to be about 25 miles 
long by 10 or 12 wide, although the best published map of the region makes it 24 
miles long by 17 wide; but as the country about has not yet been surveyed, neither 
distances nor proportions are precisely known. 
The immediate surroundings of this lake are attractive in the extreme. Beside it 
on the east lies the Mission Range of ijiountains, beginning to rise almost from the water’s 
edge, and presenting to a near view, along the lower half of the shore, a curiously reg- 
