480 Wisconsin Academy of Sciences, Aiis, and Letters. 



distal end. The first segment of the exopodite is small and 

 quadrate. The second segment has about the same width as 

 the first, and its length is about that of the second basal seg 

 ment. Its outer margin is convex and its inner sinuous. The 

 lateral spine is situated at about two-thirds the length of the 

 segment, and is commonly straight and rather weak. The ter- 

 minal hook is falciform with a regular curve, is denticulate on 

 the inner margin, and is about equal in length to the second 

 segment of the exopodite. The right endopodite is short and 

 stout, much shorter than the first segment of the exopodite, 

 setose at tip. Frequently the joint between it and the second 

 basal segment disappears, and the endopodite appears simply 

 as a prolongation of the inner distal angle of the second basal 

 segment. 



The left fifth foot reaches to the end of the second basal seg- 

 ment of the right foot. The second basal segment is quadrate, 

 its inner margin strongly convex. The lateral hair is situated 

 at the outer distal angle, is stout and plumose. The first 

 segment of the exopodite is small and trapezoidal, widest at 

 the base. The second segment is twice the length of the first, 

 armed on its inner surface with a hemispherical setose pad. 

 It terminates in two curved spines forming a forcipate struct- 

 ure. The inner spine is movable, bears a small tubercle on the 

 inner side of its base, and is setose. The endopodite is about 

 three times as long as broad, longer than the first segment of 

 the exopodite, and is setose at tip. 



Length of female, 1.4 to 2.12 mm. Length of male, 1 to 

 2 mm. (Schacht). 



Occurs only in the early spring in stagnant pools. It is 

 found quite generally in the Mississippi valley. It has been 

 found as far east as New York, as far north as Wisconsin and 

 Minnesota, as far west as JSTebraska, and as far south as Ala- 

 bama. 



D. sanguineus is a very variable species. Some of these 

 variations have been discussed in some detail by Schacht. The 

 variations do not seem to be so great, however, as necessarily 

 to raise any question as to specific identity. Inasmuch as there 



