Earring & Myers—Rotifer Fauna of Wisconsin — II. 
421 
Subfamily Tetrasiphoninae. 
Genus Tetrasiphon. 
hydrocora Ehrenberg. 
Subfamily Lindiinae. 
Genus Lindia. 
torulosa Dujardin. 
pallida Harring and Myers. 
annecta Harring and Myers. 
producta Harring and Myers. 
Candida Harring and Myers. 
tecusa Harring and Myers. 
truncata (Jennings). 
fulva Harring and Myers. 
Genus Birgea. 
Subfamily Birgeinae. 
enantia Harring and Myers 
Subfamily Dicranophorinae. 
Vol. XX, p. 630 
Vol. XX, p. 618 
.XX, p. 620 
.XX, p. 622 
.XX, p. 616 
.XX, p. 61-4 
.XX, p. 624 
.XX, p. 626 
.XX, p. 628 
Vol. XX, p. 610 
Genera: Dicranophoriis, Encentrum, Erignatha, Alhertia. 
In this regrouping we have endeavored to avoid two extremes, 
the one of including so many species in a genus that it becomes 
unnatural and lacking in homogeneity, and the other of splitting 
up the group into enough genera to make each one absolutely 
homogeneous; the latter course would probably require in this 
instance at least a dozen new genera. The result must therefore 
be accepted as a compromise, which obviously precludes the appli¬ 
cation of any hard and fast rule. The precept we have tried to ob¬ 
serve is: when only a single structural feature in one species is in¬ 
volved, a new genus is not proposed unless the departure is very 
striking; if, however, the same modification occurs in several spe¬ 
cies, in other respects apparently closely related, a new generic 
name is introduced. 
Some concrete examples may help to make this clear. Notom- 
mat a pseudocerherus has a peculiar form of mastax, quite different 
from other members of the genus, but it agrees so well with the 
normal in every other respect that it has not been separated. Much 
the same is true of N. saccigera; the pumping function of the mas- 
tax has all but disappeared, but it is so obviously derived from the 
normal virgate mastax that it seems advisable to leave it in the 
genus Notommata. Three of the smaller species, Notommata 
venusta, contort a and Uthasa, have the same type of corona, with- 
