84 Wisconsin Academy of Sciences, Arts, and Letters. 



opposite the insertion of the terminal claws. They thus cross 

 the intestine in their course. 



Color, corneous to opaque yellow. Calcareous concretions are 

 sometimes, though rarely, found in the valves. 



Everywhere common. 



This species combines the characteristics of several European 

 species. In general appearance it resembles S. serrulatus (Koch), 

 The post-abdomen is more like that of S. exspinosus (Koch), as 

 is also the macula nigra. The serration of the terminal claws re- 

 sembles that of S. vetulus (0. F, Miiller), It thus differs from I 

 S. serrulatus in two of its characteristic peculiarities — the shape 

 of the macula nigra and the serration of the terminal claws. 



SPECIES 2. 

 SiMOCEPHALUS Yetulus.. O. F. Mlillcr. 



Daphne vettjla. O. E. Miiller, Zool. Dan. Prod., N. 2399. 

 Daphnia sima. Lieven, Flsclier, Liljeborg, Leydig. 



" YETULA. Baird, 1. c, p. 95, P. X, fig. I. 



SiMOCEPHAiitrs VETULtrs. Schodler, Branch, p. 18. 



P. E. Miiller, 1. c, p. 122, PL I, figs. 26-27. 

 " " Kurz, 1. c, p. 29. 



Yery common everywhere, with the preceding species. Both 

 species are almost always taken at the same time, but the number 

 of individuals of S, Americanus is usually greater, 



G-ENUS 4. 

 ScAPHOLEBERis. Schodler, 1858. 



SPECIES 1. 



Plate 1. Fig. 7. 



SCAPHOLEBERIS MUCRONATA ( ?) 0. F. Miiller. 



Daphne mxjckonata, O. F. Miiller. Zool. Dan. Prod. No. 2404. 

 MoNOCULTJS " Jurine. Monocles, etc., p. 137. 



Daphnia " Lieven. 1. c, p. 30, T. YII, fig. 1-2. 



Liljeborg, 1. c, p. 44, T. Ill, fig. 6. 

 Scapholeeekis " Schodler. 1. c, p. 23. 



Daphnia " Leydig. 1. c, p. 187. 



P. E. Muller. 1. c, p. 124. 



Kurz. 1. c, p. 28. 

 Length, 0.7-0.8 mm. 

 I give references for the variety " fronte leevi " only, since 



