392 Wisconsin Academy of Sciences, Arts, and Letters. 
Caenis), and Trichoptera larvae (Polycentropus) in Erpobdella 
punctata, while other leeches contained Chironomid larvae, Hy- 
drachnida, Hyalella, etc. On several occasions I found small 
leeches of the genus Glossiphonia attached to the under side 
of the beetle larva Psephenus lecontei; whether the leech was 
feeding or whether it was a mere accidental relation I am un¬ 
able to say. 
8. Mollusca. (Table 5, p. 474.) 
Not all of the species occurring in the lake have been listed 
in table 5. For some reason Lamellibranchia are compara¬ 
tively little represented (if one excepts the enormous numbers 
of the minute Corneocyclas which occur in the aphytal area.) 
Amnicola limosa Say is by far the most abundant of Gastro¬ 
poda. In early summer its favorite spot seems to be the ra- 
chion (breaker line) where at a depth of two meters it covers 
the stones in immense numbers. 
The general distribution of the Gastropoda in the littoral 
area is fairly uniform. Certain species evince a preference for 
the bottom,—at least I have rarely found them elsewhere; 
while others are quite common on plants, busily feeding on the 
Oligochaeta and Chironomids. In the aphytal area I have not 
found any Mollusca except Corneocyclas; very rarely one may 
meet a specimen of Limnaea stagnalis. This is rather surpris¬ 
ing because of the fact that in so many of the European lakes, 
especially the deep alpine lakes, many Gastropoda have become 
permanently aphytal. (Forel, Roszkowski, Zschokke). 
II. ARTHROPODA. 
1. Crustacea. (Table 5, p. 474.) 
Dikerogammarus fasciatus (Smith). 
This Amphipod is confined to the rocky and stony shores of 
the lake. A relative, Gammarus limnaeus, is very abundant in 
the slack water of the springs and creeks at the western end 
of the lake, and also in the Yahara Spillway. 
Hyalella azteca (Sauss), 
As will be seen from table 5, this species is of comparatively 
wide distribution in the littoral area. Yet despite the formid- 
