a 
ENTOMOSTRACA OF MINNESOTA. 261 
The members of this genus are among the most minute forms of the 
family or the entire group. Concisely put, the characters are as 
follows: 
Form globose, not obviously truncate behind; head terminating in 
a Sharp, long, curved beak, which lies close upon the anterior margins 
of the valves; antennz short; eye larger than the pigment fleck; abdo- 
men flattened, excavated in the male; intestine with no anterior ceca, 
doubly convoluted, with an anal cecum. Three species found in Min- 
nesota. 
* Chydorus sphzericus Mueller. 
PLATE LXIV, Fias. 4, 7, 8, 10. 
Lynceus sphxricus—O. F. Muller, M. Edwards, Koch, Zaddach, Lieven, Fischer, Lill- 
jeborg, Leydig, Toth, Zenker, Fric. 
Monoculus sphericus—J urine. 
Chydorus muelleri— Leach. 
Form nearly spherical, as seen from above broadly oval; in young 
Specimens truncate behind; antennules of moderate size, in the male 
very large, with curved flagellum near the middle of anterior margin; 
pigment fleck often nearly as large as eye; beak of moderate length, 
blunt in the male; first foot strongly hooked in the male; post-abdomen 
Short, broad, rounded at the end, armed with eight or nine sharp 
teeth; shell reticulated with polygonal meshes. Color light, unspotted. 
Length 0.50 mm. 
This species occurs in spring elie: than most forms, and is ranked 
as the most abundant of the micro crustacea, being found over the 
whole circumpolar land-area. The ephippium for the winter egg was 
observed by Kurz, but the period at which it is formed seems variable. 
C. spheericus of a previous report seems to have been the following 
Species, which is more common in Minnesota in the clearer lakes. 
A small form in our large lakes measures 0.5 mm.; it may be distinct. 
* Chydorus globosus Baird. 
PLATES X XI, Fic. 23; LXIV, Fies. 1-3, 9. 
Form globose, very broad; antennules very large with a strong lat- 
eral seta on a small elevation; swimming antenne exceedingly small; 
the shell gland is well developed; the pigment fleck is much smaller 
than the eye; beak very long and incurved; post-abdomen rather long, 
more slender than the last, broader near the end which is truncate, 
bearing about 20 spines on the margin near which is a lateral series of 
minute bristles; the terminal claws are straightish, spined along the 
basal half, and have an accessory spine; the shell is very indistinctly 
