AQUATIC INVERTEBRATE FAUNA OF WYOMING AND MONTANA. 219 



On the west side a small permanent creek came in, about 30 feet wide and 2 feet 

 deep at the time of our visit, with several acres of somewhat swampy ground at its 

 mouth ; and here also were three small warm creeks (150 F. ) and one of cold water 

 (50), the latter apparently supplied by melting snow from the borders of the Pitch- 

 stone Plateau. A series of small lagoons, filled with sedge and bulrush, open into the 

 lake along this shore. The cold waters from the Eed Mountain range are diverted 

 from this lake by the course of Aster Creek, which drains the northern slope and 

 empties into Lewis Kiver, about 2 miles below the lake. 



Treacherous and stormy weather during our brief stay prevented our making 

 many collections in the open water. The dredge was hauled, in fact, but once, and 

 then at a depth of 56 feet, about a quarter of a mile' above the outlet; and even the 

 surface net was only twice used far enough from shore to give us the so-called pelagic 

 entomostraca. The remaining collections were gathered inshore, in the swamp 

 adjoining, and from streams, both warm and cool, on the western side. 



In the dredge, at 50 feet, with a bottom of fine black mud and dead vegetable 

 debris, we took quantities of the large Oammarus, a few Allorchestes, many Chirono- 

 mus larvae, specimens of Pisidium, and an undetermined annelid not preserved in 

 condition for identification. The preponderance of Gammarus was as noticeable here 

 as in the companion lake, although fewer were seen along shore in shallow water. The 

 same may be said concerning the Diaptomi taken in open water in the surface net. 

 The gigantic Diaptomus shoshone was relatively much less numerous, however, than 

 the much smaller ~D. sicilis var. It was feeding extensively upon pine pollen here, as 

 in the other lake. Although properly pelagic forms those most at home, that is, in 

 the open water and in the deeper parts of the lake and found rarely, if at all, in the 

 small lagoons these Diaptomi nevertheless extend their range close inshore, where 

 they might be seen with the naked eye in the water or taken in the net, even when 

 the surface was decidedly rough. These collections contained many examples of a 

 peculiar entomostracan (Holopedium gibberum) not noticed in Shoshoue Lake, and also 

 an abundance of a colonial rotifer belonging to the genus Conochilus allied to C. vol- 

 vox, but apparently undescribed. * 



In the Irfke, near the entrance of the warm stream on the western side, were quanti- 

 ties of young water-bugs (Notonecta), an occasional Corisa, Gammarus, Clrironomus, and 

 ephemerid larvae. Caseworms were also abundant in the lake, and the air alongshore 

 was full of two species, one black and the other pale brown, just emerged and pairing. 



From a small lagoon filled with the overflow waters of a geyser, at the western side, 

 we took with the hand net several sp( cimens of Gammarus and hydrophilid larva}, a 

 few Allorchestes dentata and young Corisa, many libellulid larva;, large and small, and 

 larva} of Agrionincc, a single small Physa, and several water-beetles (Ccelambiis). 



From a warm stream at the same place (150 F.) we have many ephemerid larva}, 

 several caseworms and a single hydrachnid, a great quantity of large and vigorous 

 specimens of Gammarus robustus, and a smaller number of 'Allorchestes dentata, many 

 examples of Pisidium, a Physa, a few annelids (Oligochcvta), and a single leech 

 (Nephelis 4-striata) not taken by us before. The Gammarus was feeding very freely 

 on dead and decaying vegetation and filamentous alga}, with some fresh vegetable 

 fragments and a little pine pollen. No traces of animal food occurred in two speci- 

 mens dissected, one half grown and the other of the largest size. 



* Described on page 256 as C. leptopus, n. s. 



