AQUATIC INVERTEBRATE FAUNA OF WYOMING AND MONTANA. 213 



From Yancey's Ranch, which we reached on the 29th, we explored Slough Creek 

 above the lower rapids, and some alkaline ponds near Baronette's Bridge, and on the 

 31st went up the East Fork of the Yellowstone to Soda Butte Station on the creek of 

 the same name. Collections were made on the way from Amethyst Creek, and from 

 the East Fork of the Yellowstone, where this creek empties into it. September 1 we 

 spent near Soda Butte Station, at work in the creek and in Trout Lake 2 miles 

 north of the " station." Returning to Yancey's September 2, we examined the over- 

 flow waters of the creek and searched the East Fork thoroughly at the Soda Butte 

 bridge, and finished our collections from the river in that vicinity. 



On the 3d and 4th we continued to the cafion and to the lake. The 5th was 

 spent in making shore collections from Stevenson Island in Yellowstone Lake 

 and in an examination of the small ponds and bayous of the island itself. On the 

 forenoon of the 7th we finished our work on Yellowstone Lake by making three hauls 

 of the dredge from the little steamer Zillah in the vicinity of Stevenson Island, at 

 depths varying from 20 to 198 feet. 



The work of the season closed, September 10, with collections made from two 

 localities previously examined by Prof. Evermann with reference to establishing a 

 fish-hatchery Bridger Creek and a cold spring adjacent, near Bozeman, and some 

 springs and small streams near Boteler's Ranch, just north of the Park. The return 

 trip was made by the Northern Pacific Railroad, September 10 to 13. 



The collections of this summer were made under 73 collection numbers, represent- 

 ing 23 localities. 



Apart from the practical points aimed at, and the opportunity to further extend 

 our knowledge of the aquatic life of Yellowstone Park, a region whose zoology must 

 long have an exceptional interest, I value the results of this year's work chiefly as 

 affording the means for a comparison of the animal life of two lakes so similar in 

 many respects as Flathead and Yellowstone, and yet widely contrasted in altitude, in 

 geological surroundings, and in topographical and geographical relations. It is, in my 

 judgment, by a thorough examination and critical comparison of typical situations like 

 these that the most interesting and immediately fruitful additions to zoological science 

 are to be made in this field. I have only to wish that a longer stay on each of these 

 lakes might have made possible a more minute and exhaustive study of their animal 

 life and its relations to varying conditions of depth, bottom, temperature, season, 

 weather, bionomic association, and the like. 



DISCUSSION OF THE COLLECTIONS. 



While the partial and, in most cases, merely preliminary way in which the mate- 

 rial of these expeditions has as yet been studied makes any full discussion of the 

 results impossible, it seems best that a report of progress should be made, presenting a 

 summary review of the invertebrate life of these waters in the midsummer season, with 

 descriptions or determinations ot such new or particularly abundant and important 

 kinds as have thus far been made out. Such a statement will include, in fact, the 

 greater part of the economic results of immediate utility, and may be said, therefore, 

 to fulfill the leading object of the work. This report may be most conveniently cast 

 in geographical form, the life of each river system being separately discussed ; but, for 

 want of time to examine the entire mass of the collections, only a preliminary account 

 of the fauna of the still waters visited, from temporary pools to Flathead and Yellow 

 stone lakes, will be given at present. 



