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; antennae short; eye larger than the pigment fleck; abdo- 

 men flattened, excavated in the male; intestine with no anterior caeca, 

 doubly convoluted, with an anal coecum. Three species found in Min- 

 nesota. 



* Chycloriis sphajricus Mueller. 



Plate LXIV, Figs. 4, 7, 8, 10. 



Lyncetis sphxricus — O. F. Miiller, M. Edwards, Koch, Zaddacb, Lieven, Fischer, Lill- 



jeborg, Leydig, Toth, Zenker, Fric. 

 Monoculus sphsericus — Jurine. 

 Chydorus niuelleri — 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 Qgg was 

 observed by Kurz, but the period at which it is formed seems variable. 



C. sphcericus 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 0.3 mm. ; it may be distinct. 



* Chydorus sriobosus Baird. 

 Plates XXI, Fig. 23; LXIV, Figs. 1-3, 9. 



Form globose, very broad; antennules very large with a strong lat- 

 eral seta on a small elevation; swimming antennse 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 loug, 

 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 



