^16 TWELFTH j\NNUAL KEPORT, 



Sp. 1. Chydorus sphiericus, Mueller. 



(Plate F. Figs. 4, 7, 8 and 10.) 

 Lynccus sphcuricus, o. f. mueller, m. edwards, koch, zaddach. lieven, Fischer 



rjLLJEBOBG, LETDIG, TOTH, ZENKER, FRIC. 



Monoculus splicvriciLs, jurine. 



Chydorus muelleri, leach. 



Chydorus sphtericus, baird, schoedler, p. e. ivruELLEE. ltjtz, kurz, birge. 



Form nearly siDlierical, as seen from above broadly oval; in young 

 specimens truncate behind; anteuuules of moderate size, in the male 

 very large, with curved flagellum near the middle of anterior mar- 

 gin; 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 S — 9 

 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 hnd-area. The ephippium for the 

 winter egg was observed by Kurz, but the period at which it is 

 formed seems variable. 



C. sphaericus of a previous report seems to have been the follow- 

 ing 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. 



Sp. 2. Cliydorus globosus. Band. 



(Plate F. Figs. 1,2, 3 and 9.) • 



C?!l/d0/H.S £f?0?)OS)iS, BAIRD, LILLJEBORG, SCHOEDLEK, LEYDIG, P. E. MUELLER, FRIC, 'f^ 

 KURZ, BIRGE. ,^i 



I 



Form globose, very broad; antenuules very large with a strong f 



lateral seta on a small elevation; swimming antennse exceedingly i 



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 j" 



is truncate, bearing about 20 spines on the margin near which is a ;' 



lateral series of minute bristles; the terminal claws are straightish, i 



spined along the basal half, and have an accessory spine; the shell } 



is very indistinctly reticulated and spotted; color dark; length 0.7- ^ 



0.8 mm.; male 0.55 mm. The males have the abdomen very nar- |; 

 row for the entire length. 



This species is considered rare elsewhere, but is not infrequent in 

 August near Minneapolis. 



