AS) eed! sea en eee 
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; antenne 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—Jurine. 
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 earlier 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 XXI, Fie. 23; LXIV, Fias. 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 
