AQUATIC INVERTEBRATE FAUNA OF WYOMING AND MONTANA. 
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water beetles {Hydrophilidce and Dytiscidce), and perlid and ephemerid larva 1 , together 
with a number of leeches — both Clepsine and Hephelis — Physa , Limncea , PlanorMs, 
Pisidium , Gammarus , Plumatella , and a fresh water sponge (Spongilla fragilis Leidy). 
Swan Lake. — This lake, visited August 24, lies in the course of the river of the 
same name, about 8 miles from our camp on Flathead Lake. It is a long and narrow 
lake — about 12 miles long by 1 to 3 miles wide, according to our guide — lying deeply 
secluded between two lofty mountain ranges, Mission Range on the west and the Koo 
tenai on the east. Its waters are clear and its bottom is extremely irregular, if one 
may judge from the soundings made by us at the lower end, for some 2 miles above 
the outlet. The deepest water (not exceeding 30 feet) lay off the highest points, where 
the mountains come down to the water’s edge, or in pot-holes and winding irregular 
channels, with weedy bars and banks between. At the upper end, the lake is said to 
expand to its greatest width and to be surrounded by meadows and marshy flats with 
water weeds extending a long distance out; and there are similar weedy flats along 
the shore below, especially at the mouths of creeks. Swan River, above the lake, was 
also reported to be marshy for some distance up, as is also Spring Creek, emptying 
near the head of the lake. About half a mile above the outlet were two small islands 
with gravel beaches and surrounded by shoal water full of rushes and a good growth 
of other aquatic plants. 
The animal species in the deep open water of this lake were precisely the same 
as those commonest in the larger lake below; namely, Daplmia thorata, Epischura 
nevadensis , var. Columbian , taken in numbers, and Leptodora hyalina , occurring only 
occasionally. These pelagic entomostracans were, however, much less abundant in 
Swan Lake than in the larger, deeper body of water. 
The bottom forms were not collected by us, as we had brought no dredge, but the 
surface net was hauled repeatedly among the weeds in water about 10 feet in depth, and 
stones, round and small, around the margins of the islands were thoroughly searched. 
Among the weeds, the commonest entomostraca were Sida crystallina, Eurycercus 
lamellatus , and Cyclops gyrinus — the latter numerous — and with these occurred a very 
few specimens of />. thorata and of a species of Alona undetermined. A few small 
Chironomus and ephemerid larvae, Corisa , Agrion larvae, Allorchestes dentata , Physa , 
PlanorMs , Hydrachnidce , several bristled annelid worms, and a small leech, were also 
taken here. From the stones along the margin of the island we took great numbers 
of Gammarus and Cypris , a very fine sponge occurring in tliickish masses on the rocks 
(some white and some chloropliyl- green), a branching polyzoan ( Plumatella ) clinging 
to the stones, several species of leeches, — including Nephelis macula to, so common in 
the Park, — planarians, specimens of Physa , PlanorMs, and Pisidium , and the usual 
aquatic insect forms, larval and adult; viz, larval Ephemeridce and Chironomus and 
other small dipterous larva;, Corisa , aquatic Coleoptera , Hydrophilidce , Dytiscidce , and 
several kinds of caseworms. These alongshore collections were, in fact, decidedly 
larger and more varied than those from Flathead Lake, a fact doubtless to be ex- 
plained in part by the relatively greater amount of shallow weedy water, and the 
consequent greater abundance of minute plant and animal life. 
