AQUATIC INVERTEBRATE FAUNA OF WYOMING AND MONTANA. 239 



water beetles (Hydrophilidce and Dytiscidce), and perlid and ephemerid larvae, together 

 with a number of leeches both Clcpsine and Ncphelis Physa, Limncca, Planorbis, 

 Pisidium, Gammarim, Plumatclla, 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 ou 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 Kange 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 

 expaud 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, Daphnia thorata, Epischura 

 ncvadensis, var. Columbia;, taken in numbers, and Leptodora hyalina, occurring only 

 occasionally. These pelagic entomostracans were, however, much less abundant in 

 Swau 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 eutomostraca were Sida crystallina, Eurycercus 

 lamellatus, and Cyclops gyrinus the latter numerous and with these occurred a very 

 few specimens of D. thorata and of a species of Alona undetermined. A few small 

 Chironomus and ephemerid larvae, Gorisa, Agrion larvae, Allorchestes dentata, Physa, 

 Planorbis, 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 flue sponge occurring in thickish masses on the rocks 

 (some white and some chlorophyl-green), a branching polyzoan (Plumatella) clinging 

 to the stones, several species of leeches, including Nephelis maculata, so common in 

 the Park, planarians, specimens of Physa, Planorbis, and Pisidium, and the usual 

 aquatic insect forms, larval and adult; viz, larval Ephemeridce and Chironomus and 

 other small dipterous larvae, Gorisa, aquatic Goleoptera, Hydrophilida;, Dytiscida;, 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. 



