Diaptomus Birgei. 
17 
armed with fine serrulations on its inner margin. The inner 
ramus is one-jointed, equalling in length the first joint of the 
of the outer ramus. 
The left fifth foot of the male reaches slightly beyond the firsq. 
joint of the outer ramus of the right. The basal joint is quad¬ 
rangular, considerably shorter than the right basal joint. The 
first joint of the outer ramus is about twice as long as broad. 
The second joint is slightly longer than the first joint; it is ex¬ 
panded at base, where it is armed with fine hairs, and termi¬ 
nates in a finger-like process bearing a falciform spine. The 
inner ramus extends to about one-half the length of the second 
joint. 
Length of female, 1.5 mm. ; male, 1.3 mm. 
The material in which this species was found was collected by 
Professor E. A. Birge at New Lisbon, Wisconsin, and only a few 
individuals were found. I have expected to find it in the collec¬ 
tions from other Wisconsin localities; but so far my search has 
been without success. It is a clearly marked species resembling 
the European D. gracilis Sars more closely than does any other 
described American species. The characters of the fifth feet, 
however, separate it from the European form. 
I have taken the liberty of naming this species in honor of 
Professor Birge, to whose kind assistance and encouragement I 
have been greatly indebted. 
Ripon , Wis. 
