300 The American Naturalist. [April, 
straight as in the figures by Herrick of S. daphnoides, and the 
general outline of the body almost as daphnia-like in appear- 
ance. 
Eylmann in the “ Berichte der Naturforschenden Gesellsch- 
aft zu Freiburg” Zweiter Band, Drittes Heft, published in 
1886, figures the lower margin of the head of S. vetulus straight 
to the short beak, and the body with greatest height at the 
middle. A specimen of &. vetulus identified by G. O. Sars, of 
Norway, and examined by the author has the lower margin of 
the head straight to the very short beak and the eye situated 
at a distance from the lower margin equal to about one-half 
the diameter of the eye. 
Herrick says in his description that the curved spines present 
in the other species at the caudo-ventral angle of the shell are 
absent from S. daphnoides. If this be constant it seems to be 
the only character not possessed by specimens of S. vetulus. 
The specimens taken in Manitoba, and also in Iowa, vary in 
size, and shape of the head and of the body; there are such 
grades of variation, and authors figure such differences of form 
‘in S. vetulus; that it seems very probable that S. daphnoides is 
merely an extreme form of S. vetulus. 
Bosmia longirostris: Found in only two collections ; one from 
Lake Manitoba and the other from a slough at Portage la 
Prairie. 
Macrothria laticornis: This species was met with only in a 
shallow prairie slough and was by no means abundant. 
Bunops scutifrons: This beautiful species was found rather 
frequent in the shallow prairie slough at Portage la Prairie. 
Iliocryptus sp.?: A few shells and one individual of this 
genus were taken from the Assiniboin River. The species is 
probably longiremus Sars. 
Alona quadrangularis: Alona costata: There is some ques- 
tion as to the identification of these two species. Only a single 
individual of each was found. The specimen that may be 
Alona costata is not strongly striated but other characteristics 
agree with descriptions of this species. 
Graploleberis testudinaria var. inermis: Although taken at 
three different places this species was rare. A few individuals 
