AQUATIC INVERTEBRATE FAUNA OF WYOMING AND MONTANA. 237 
alar series of high, scantily wooded ridges and rocky gulches transverse to the length 
of the lake. Further back the peaks of the higher mountains rise bare and steep. 
This Mission Range diminishes in height northward, and falls away to Swan River, 
near the northeast part of the lake, but across the river to the east and north the 
Kootenai Range continues far up along the Flathead. Opposite Mission Range, on 
the western side of the lake, lies a mass of heights between mountain and hill, rising 
one above another, mostly wooded, 1 >ut with occasional park-like openings. Above the 
lake a level valley several miles wide, partly densely wooded and partly prairie, extends 
above Kalispell, and to the south lies the naked plateau of the Flathead Reservation. 
The principal tributaries are the Flathead, a still, broad river, larger than the 
Yellowstone at the lake, running from Demersville, most of the way between hat, low 
banks; the Big Fork or Swan River, a rocky stream, whose course from Swan Lake to 
the Flathead is an oft-repeated alternation of wild rapids and comparatively quiet 
reaches; and Dayton Creek on the west, which 1 did not see. The outlet (Flathead 
River) Hows rapidly away from the lake between bluffy banks which presently become 
a canon. 
Although this lake lies in a great trough-like valley, the level of much of which is 
not far above that of the lake itself, there is scarcely any swampy ground in its vicin- 
ity, or weedy standing water connected immediately with it or with its tributaries 
in the vicinity of the lake. The principal breeding -grounds of fish, in fact, appear to 
be upon these streams at a considerable distance from Flathead Lake, so that for most 
of the species there is a long migration period. 
Our systematic work in the lake was all done in and about the northeast bay in 
the vicinity of the mouth of the Big Fork, and at the lower end near the outlet. 
While on this bay we were the guests of Mr. E. L. Harwood, of Demersville, and 
of the Helena Rod and Gun Club, whose club-house on the bay was our home, while 
a steam launch belonging to members of this club afforded the only possible means 
of access with our apparatus to the deeper waters of the lake. 
At this locality, where we remained from the 20th to the 22d of September, two 
dredgings were made, the first beginning at 70 feet and continuing to 125 feet, and 
the second beginning at 125 feet and continuing to 153 feet. The surface net was 
hauled from S a. m. to 9 p. in., in deep and shallow water, and collections were made 
with nets and by hand alongshore, among the weeds, from drift wood, and from stones. 
Our only temperature observations were made at noon of a bright day (September 
22), with a common thermometer only, as no deep-sea thermometer was furnished for 
this trip. At this time the temperature of the air was 70° F., that of the water at 
the surface 68°, and that of the mud brought up in the dredge, in a haul commencing 
at 125 feet and stopping at 153 feet, was 42°. 
At the lower end of the lake a heavy storm made work difficult, but we searched 
thoroughly a rocky flat at the outlet, and collected from the masses of weeds washed 
up by the waves and from the weedy shallows along the southeast shore. 
The open-water collections in Flathead Lake were very similar in general charac- 
ter and in the relative numbers of the principal groups to those in Yellowstone Lake, 
but the species were all different. In the former lake the so-called Daphnia pulex 
was not once seen, but this species was replaced by a Daplmia allied to hyalina , and 
here described as thorata. This entomostracan made probably four-fifths to nine- 
