234 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
MADISON RIVER SYSTEM. 
Although large collections were made from streams of various sizes whose waters 
find their way into the Missouri by way of the Madison, the only lakes so connected 
upon which we worked were Mary Lake and Grebe Lake, the former draining through 
Nez Perce Creek into the Firehole, and the other giving origin to the main branch of 
the Gibbon. 
Mary Lake . — This little lakelet, situated at a level of 8,200 feet, on the divide 
between the waters of the Firehole and those of the Yellowstone, is an oval body of 
water some 5 or 6 acres in extent, clear but shallow, with a fine gravelly beach 
and very little vegetation. The immediate banks are rather steep, and the country 
around is densely wooded with pine. The greatest depth at our visit was only 20 
feet, and a lagoon-like bay near the lower end was but 5 or 6 feet deep. Both inlet 
and outlet — the former very small — were dry, but the lake overflows into Nez Perce 
Creek when the snow goes off in spring. 
Our collections from this lake were particularly remarkable for the great number 
of one of the most beautiful and interesting of our fresh water entomostraca, the 
species known as Holopedium gibberum. In a haul made with the towing net at the 
surface, in the shallow water near the outlet, a great quantity of this species was taken, 
together with a still greater number of Diaptomus lintoni and an occasional Corethra 
larva. The sun was shining at the time (11 a. m., August 11) and the water was 
rippled by a light breeze. Near the bottom, at a depth of 16 feet, T). lintoni was the 
prevailing form, mingled, however, with an almost equal quantity of Corethra larvae 
and a considerable number of Daplinia schoedleri. 
The deeper bottom was of sandy mud, which contained a large number of Chi- 
ronomus larvae in tubes — most of them the common large red species — a great number 
of the common form of Pisidium, and many caseworms with tubes composed of sand 
grains, several of them bicarinate. The dredge brought up a little Spongilla, several 
of the usual annelids, and Corethra larvae, but no living vegetation. No amphipods 
were taken from the lake, and no univalve mollusks. An unusual number of aquatic 
insects occurred alongshore, most of them specimens of Agabus (two species) and 
Deroneetes griseostriatus. The leeches were, as usual, several species of Clepsine and 
Nephelis maculata. 
Grebe Lake . — This shallow, muddy lake, connected with the head waters of Gibbon 
River, is so far secluded within the forest that it has no current name, and is locally 
almost unknown. We reached it August 27, with saddle and pack animals, from the 
Grand Canon Hotel, carrying canvas boat, seines, and our smaller apparatus. 
