190 Marsh — Cyclopulce and Calanidm of Wisconsin. 
American entomostraca, made his collections in Illinois, south¬ 
ern Wisconsin, the Great Lakes, and Montana and Wyoming. 
Prof Cragin collected in eastern Massachusetts. Prof. Her¬ 
rick has collected very widely through the Mississippi valley 
and the southern states. His reports on the Minnesota Crus¬ 
tacea (22, 25, 26) covered a region with a fauna nearly iden¬ 
tical with that of Wisconsin. His work of exploration must 
have been done very thoroughly, for my work in Wisconsin 
gives me little to add in the way of new species. Because of 
incomplete descriptions or a lack of figures, it is, in some- 
cases, however, difficult to identify his species. 
In Wisconsin the cladoceran fauna is better known than in 
any other part of the United States through the well-known 
work of Prof. Birge, but the copepoda have been almost en¬ 
tirely neglected. 
While the number of copepods in a collection from any 
locality is frequently very large, the number of species is 
generally small. In pools which are swarming with individ¬ 
uals, frequently there are not more than two or three species. 
In pelagic collections there are seldom more than four to six 
species. Of diaptomus there is ordinarily only one species in 
a locality, although two or three species are sometimes found 
together in pelagic collections. 
Some species ot copepods may be considered strictly pelagic,, 
and some as strictly littoral, while others are found only in 
stagnant pools. But many species readily adapt themselves to 
all these conditions, and with little or no change of structure 
seem to thrive equally well wherever they may be. 
The following may be considered a fairly accurate division 
of the species according to their habitat: 
