448 Wisconsin Academy of Sciences, Arts, and Letters. 



ment of the exopodite almost three times as long as broad ; sec- 

 ond segment about as long as the first and for about the prox- 

 imal third nearly as wide, but beyond this considerably broader. 

 Marginal spine near the outer distal angle ; straight, very 

 strong and thick, a little less than half as long as the seg- 

 ment. Terminal hook rather short and very stout, irregularly 

 curved, heavily and closely denticulate at the distal half of the 

 inner margin. Endopodite of the right fifth leg spatulate, not 

 nearly reaching the middle of the first segment of the exopo- 

 dite; apex rounded, armed with a few strong spines. 



"Second basal segment of the left fifth foot armed at the outer 

 margin, a short distance above the distal angle, with a short, 

 thick, pointed spine. First segment of the exopodite about 

 three times as long as wide, armed at the distal third of the inner 

 margin with a few strong hairs. Second segment about half 

 as long as the first, having on the inner margin two cushion- 

 like processes (the upper, smaller one hairy, and the lower 

 densely tuberculate), and being armed at the tip with two proc- 

 esses forming a forcipate structure, the outer broad, plowshare- 

 shaped, the inner a long and narrow spine, hairy within. En- 

 dopodite of left fifth foot one-segmented, of the same width, 

 throughout, with a broadly rounded tip ; inner margin rugose. 



"Length of female, 4 to 4.5 mm. Length of male, 3,5 to 

 4 mm. 



"This Diaptomus is the largest of the American species and 

 a very beautiful one. Dr. Forbes states in his original descrip- 

 tion that all were red throughout. Specimens taken in April, 

 1897, from ponds south of LTrbana, Illinois, when they were in 

 the height of sexual activity, were colored as follows ; thorax 

 and anterior appendages (all but the first pair of antennae) 

 blue; first pair of antennae, fifth pair of legs (in the male), 

 and abdomen red. In the female all the legs were blue." 



The preceding description was taken from Schacht and was, 

 presumably, prepared under the supervision, or with the co- 

 operation, of Professor Forbes. I have been unable to obtain 

 any of the Illinois material for verification of the description, 

 and the species has not occurred in the territory from which 



