GEOLOGICAL SURVEY OF THE TEEEITOEIES. 97 



ever saw. Some of the curves are as perfect as if drawn by the hand 

 of art. Our little boat performed most excellent service. A suitable 

 frame- work was fastened in the stern for the lead and line, and with the 

 boat, a system of soundings was made that gave a very fair idea of the 

 average depth of the lake. The greatest depth discovered was 300 feet. 

 It is fed by the snows that fall upon the lofty ranges of mountains that 

 surround it on every side. The water of the lake has at all seasons 

 nearly the temperature of cold spring-water. The most accomplished 

 swimmer could live but a short time in it; the dangers attending 

 the navigation of such a lake in a small boat, are thereby greatly in- 

 creased. The amount of vegetable matter in the lake is enormous. At 

 certain seasons of the year, the waves throw upon the shore a windrow 

 of drifted vegetation. Frequently, after a strong wind, the water of the 

 entire border of the lake for several yards from the shore will be filled 

 with minute fragments of vegetation broken by the waves, rendering 

 the water quite impure. Several species of plants grow far out into the 

 deep waters, and I have seen them growing thickly on the rocks at the 

 bottom 10 to 20 feet in depth. We were able to discover but one species 

 of fish in the lake, and that was trout, weighing from two to four 

 pounds each. Most of them are infested with a peculiar intestinal worm, 

 which has been described by Dr. Leidy, in a subsequent portion of this 

 report, as a new species, under the name of Bihoiliriwn cordiceps. 

 I directed Mr. Campbell Carrington, naturalist to the expedition, to pre- 

 pare the following notes on this subject : 



The Trout of Yellowstone Lake. — "Although I searched with 

 diligence and care in the neighboring streams and waters around the 

 Yellowstone Lake, 1 was unable to find any other species of fish except 

 the salmon-trout; their numbers are almost inconceivable; average 

 weight, one pound and a half; color, a light-gray above, passing into a 

 light-yellow below ; the fins, all except the dorsal and caudal, vary from 

 a bright- yellow to a brilliant orange, they being a dark-gray and heavily 

 spotted. A curious fact, and one well worthy of the closest attention 

 of an aspiring icthyologist, is connected with these fish, namely, that 

 among their intestines, and even interlaced in their solid flesh, are 

 found intestinal worms, varying in size, length, and thickness, the 

 largest measuring about six inches in length. On cutting one of these 

 trout open, the first thing that attracts your attention, are small oleagin- 

 ous-looking spots clinging to the intestines, which, on being pressed^ 

 between the fingers, break and change into one of these worms, small, 

 it is true, but nevertheless perfect in its formation. From five or six 

 up to forty or fifty will be found in a trout, varying, as I said before, in 

 size, the larger ones being found in the solid flesh, through which they 

 work their way, and which, in a very short while, becomes almost pu- 

 trid. Their number can generally be estimated from the appearance ot 

 the fish itself; if many, the trout is extremely poor in flesh, th^ color 

 changes from the healthy gray to a dull pale, it swims lazily near the 

 top of the water, losing all its shyness and fear of man ; it becomes 

 almost savage in its appetite, biting voraciously at anything thrown in 

 the water, and its flesh becomes soft and yielding. If, on the other 

 hand, there are few or none, the flesh of the fish is plump and solid, 

 and he is quick and sprightly in all his motions. I noticed that it was 

 almost invariably the case when a trout had several scars on the out- 

 side of his body that it was free from these worms, and I therefore took 

 it for granted that the worms finally worked their way through the 

 body, and the flesh, on healing up, leaves the scars on the outside ; the 

 trout, in a short while, becomes plump and healthy again. The jonly 

 7 a s 



