116 TWELFTH AN"NUAL BEPORT. 



Sp. 1. Chydorvis sphsericus, Mueller. 



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

 Lyncexis sphccricus, o, r. mueller, m. edwards, koch, zaddach. lieven, fischer 



LILLJEBOEG, LETDI&, TOTH, ZENKER, FRIC. 



Monoculus sphcericui), jurine. 



Chydorus muelleri, leach. 



Cliydorus sphcericus, baird, schoedler, p. e. muellee. lutz, 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 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 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. Chydorus globosus, Baird. 



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



Chydorus glohosiis, baird, lilljeborg, schoedler, leydig, p. e. mueller, fric, 

 g kurz, birge. 



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

 lateral seta on a small elevation; swimming antennae 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. 



