116 TWELFTH AXNUAL REPORT. 



Sp. 1. Cliydoriis sphsericvis, Mueller. 



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

 Lynceus splucricus, o. f. mdeller, m. edwards, koch, zaddach. lieven, fischek 



LILLJEBORG, LETDIG, TOTH, ZENKER, FKIC. 



Monoculus sphccricus, jurine. 



Chydorus muellcri, leach. 



Chydorus sjjhccricus, baird, schoedler, f. e, jiteller. ldtz, kurz, birge. 



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 mar- 

 gin; pigment fleck often nearly as large as ej^e; 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 8 — 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 Irnd-area. The ephippium for the 

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

 formed seems variable. 



C, sphsericus 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. Cliyclorus globosus, Baird. 



(Plate F. Figs. 1,2, 3 and 9.) 

 Chydorus glohosus, baird, lilueborg, schoedler, leydig, p. e. jideller, fric, 



KURZ, BIRGE. 



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

 lateral seta on a small elevation; swimming antenna 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 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. 



