474 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Lake Geneva, in Walworth County, Wisconsin, is a clear and beautiful sheet of 
water about 7 miles long by in greatest width, with an extreme depth, according 
to my soundings, of 132 feet. It is a glacial lake, lying in a trough-like valley of 
the drift, the southern side of which formed part of the terminal moraine of the 
great Lake Michigan glacier. The valley is continued westward with a very gradual 
rise beyond the head of the lake, where a small stream empties its clear, cool water. 
By way of the outlet at its eastern end, its waters pass through Fox Eiver into the 
Illinois. Its banks are high and rolling, but nowhere bluify, and there is no rock 
anywhere in sight. The slopes of the bottom are mostly gradual, but off the “points” 
they may reach, for the first 500 or 600 feet, a descent of 1 foot in 5; while in the 
bays this is only about 1 in 50.* 
The vegetation of this lake is chiefly confined to a narrow belt along the shore, 
except in Williams’ Bay on the north side and in the shallow water near the outlet. 
In the deepest parts the bottom is perfectly destitute of living plants higher than 
diatoms, and there is also a remarkable scarcity and small variety of animal life in 
this situation. 
In the shallow water, from the shore to a depth of 5 fathoms, the most abundant 
plants observed in 1881 were as follows : Myriophyllum heterophyllum, M. scabratum, 
Ceratophyllum demersum, Potaniogeton conipressum, P. lucens, P. pauciflorum, Anacharis 
canadensis^ and Chara contraria.f 
Swimming and creeping among the somewhat scanty growth of these aquatic 
plants, was a small variety of animals, the most abundant of which were the smallest 
of our common amphipod crustaceans ( Allorcliestes dentata Smith) andthelarvm of an 
abundant genus of gnats — Chironomus. A partial examination of the material col- 
lected by a dozen hauls of the dredge in this shallow water gave me the following 
imperfect list : 
SHALLOW WATER COLLECTIONS, 1881. 
INSECTA. 
1. Paraponyx sp.? An interesting aquatic caterpillar, richly provided with tufted tracheal gills on all 
surfaces of the body, probably belongs to this genus of pyralid Lepidoptera. Two examples 
were taken among weeds growing on a gravelly bottom, in water 6 feet deep. 
2. Stenelmis orenatus Say. Several adult specimens of this beetle were taken in a haul along shore, 
doubtless from the aquatic weeds. 
3. Bytiscidw. A single larva. 
4. Chironomus sp. Very many specimens of small white larvae belonging to undetermined species of 
these very abundant gnats. 
5. Phryganeidas. Various caseworms, mostly Leptoceridae, with sand tubes, either straight and slender 
or short and curved. Tubes sometimes made of a webbed membrane covered with a thick layer 
of small spherical colonies of Rivularia or other similar Algae. A remarkable larva of Lage- 
nopsyche frequently occurred, the case transparent and commonly covered with diatoms. A 
single specimen of Sericostomidae. 
6. Agrionina and Libellulina. Nymphs of dragon flies. 
7. Ephemeridce. Most commonly nymphs of Ccenis, of an undetermined species. 
CRUSTACEA. 
8. Camharus virilis Hagen. Cray-fishes were not at all abundant in this lake, but a few young speci- 
mens of this species were taken in the dredge. 
* See profiles, page 476. 
t Determined for me by Prof. T. J. Burrill, of the University of Illinois. 
