70 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



would not give to the lakes a decided faunal peculiarity to differ- 

 entiate them from those just described. 



Morainal lakes, from about 40 of which I have made collections, 

 are most abundant between 9,000 and 10,500 feet. These lakes, 

 very numerous in some localities, are inclosed by a network of 

 morainal ridges, usually timbered, varying from a few feet to about 

 100 feet in height. Most of them are small, many of them mere 

 ponds, and few are more than a few feet deep. They represent 

 all stages of filling with silt and obliteration by growing vegetation. 

 At one extreme are those with clean gravel bottoms and at the other 

 marshes, where the water is entirely hid by plant growth, or meadows 

 and thickets where the process of filling has produced dry land. 

 None of these lakes are on large streams and most of them receive 

 only the surface water from the small basin bounded by the sur- 

 rounding ridges. Many never have any outflow and others only 

 at times of high water. They are chiefly of a stagnant character, 

 in strong contrast to those on the direct course of the streams, and 

 the water is frequently of a dark brown color, due to the decaying 

 organic matter on the bottom. (See lower fig., pi. 13.) 



CHmatic conditions are much less rigorous than in the lakes at 

 higher elevations. I have not observed the time of the melting of 

 the ice in the spring, but inquiries among people hving in this region 

 place it at about the last of April, and freezing in the fall is probably 

 in October or November. Water temperatures of 55° to 65° F. are 

 common in June, July, and August, while in some of the lower ones 

 70° or exceptionally 80° have been recorded. (See fig. 8.) 



It is to be noted that aU of these lakes are included in the western 

 or higher half of the area between the Continental Divide and the 

 plains, and that in the eastern portion (the foothiU area), to which 

 glaciation did not extend, there are very few bodies of standing 

 water of any sort. Accordingly data from elevations between 5,400 

 and 8,000 feet are wanting. 



METHODS. 



In the plains region no special difficulties are experienced in col- 

 lecting, but in the mountains, especially in the higher and rougher 

 portions, the work involved in getting from lake to lake is great. 

 Many of them can be reached only on foot, and my practice was to 

 make trips of two or three days, carrying food, blankets, and the 

 necessary collecting materials. For such work I reduced the col- 

 lecting outfit to a size which was carried in an Army haversack with 

 special pockets sewed in for vials, etc. 



A conical net of No. 10 bolting cloth was used. It was 16 inches 

 long, with an opening of 5 inches, supported by a stout wire ring, 

 to which a long cord was attached by three shorter ones. In the 

 bottom of the net, instead of the screw cup of Dr. E. A. Birge, I em- 



