262 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
reticulated and spotted; color dark; length 0.7 to 0.8 mm.; male 0.55 
mm. The males have the abdomen very narrow for the entire length. 
This species is considered rare elsewhere, but is not infrequent 
near Minneapolis during August. 
Chydorus ovalis Kurz. 
PLATE LXIV, Fie. 11. 
Form oval, nearly twice as long as high; beak long; antennules 
two-thirds as long as the beak, with one elongated sensory filament 
above the others; pigment fleck nearly as large as the eye; antenne 
small; shell margins heavily fringed anteriorly; post-abdomen of mod- 
erate size, rounded at the end, with about eight teeth near the end; 
shell smooth. Length 0.4 mm. 
This species is rather near C. sphericus, differing in having the 
shell smooth, antennz shorter and beak longer. This species is not 
yet known in America. From C. Jatus it differs in the single anten- 
nulary flagellum and number of anal teeth. 
* Chydorus czelatus Schoedler. 
PLATE LXIV, Fie. 12. 
Chudorus adunctus—Schoedler. 
This small species is about 0.4 mm. long and resembles the young 
of C. globosus in form, from which as well as from all known species it 
is distinguished by the markings of the shell, which consist of series 
of rounded elevations (or depressions?) arranged parallel to the lower 
margins of the shell and head. The description is very incomplete, 
and the only other author who appears to have seen the animal is Kurz, 
who adds that the sensory filaments of the antenne are unequal in 
‘height, and that the so-called elevations are really depressions. A 
form with a few depressions about the edge and characters of this 
species was once seen in the vicinity of Minneapolis. This is probably 
a variety of OC. sphericus. 
Chydorus nitidus Schoedler. 
PLATE LXIV, Fias. 5, 6. 
Shell smooth and regularly punctate; the head resembles C. speri- 
cus, but the pigment fleck is much smaller than the eye, to which it is 
much nearer than to the end of the beak; the post-abdomen is broader 
near the end, and bears a row of 10 to 12 teeth on either side. 
Chydorus latus Sars. 
Of moderate size, oval, rounded behind. A slight depression be- 
tween head and body. Beak long, slender and curved. Macula quad- 
