462 Wisconsin Academy of Sciences, Arts, and Letters. 



Length of female, 1.182 mm. Leng'th of male, 1.115 mm. 



This species was found in materia:! collected by Professor 

 H. B. Ward in Dead lake, Lake Michigan, Lake Rocks, and 

 Mirror lake, — all these lakes being in the vicinity of Pike's 

 Peak. It was especially abnndant in the collections from 

 Lake Michigan. 



DIAPTOMUS VVASHINGTONEKSIS Sp. no7. 



Plate XXII, figs. 5, 8, 9. Plate XXIII, fig. 2. 



One of the smaller species. The first cephalothoracic seg- 

 ment is somewhat longer than the combined length of the three 

 following segments. The last cephalothoracic segment is 

 armed Avith minute lateral spines. The first segment of the 

 female abdomen is as long as the rest of the abdomen. It is 

 expanded laterally and in front and bears two small spines 

 laterally. On the posterior end on the right side it bears a 

 finger-like process projecting backward. The second segment 

 is ordinarily about one-half the length of the third. The furcal 

 rami are about twice as long as their Avidth and are setose on 

 the inner margin. 



The antennae are 25-segmented, slightly longer than the en- 

 tire body. The right male antenna is much sv/ollen anterior 

 to the geniculating joint, and the antepenultimate segment 

 bears a recurved hook which is continuous with a lateral la- 

 mella extending back one-half the length of the segment. 



The first basal segments of the female fifth feet are armed 

 with rather large spines. The lateral hairs of the second basal 

 segments are very long and slender. The exopodite is composed 

 of two segments, the third segment being represented by two 

 small spines. In addition to these spines, there are sometimes 

 present two other ver}^ minute spines. The second segTiient is 

 prolonged into the customary book, vrhieh is denticulate on the 

 inner margin. The endopodite is slightly longer than the 

 first segnnent of the exopodite, is composed of one segment, and 

 armed on the inner margin of the tip with hairs, and has two 

 rather long terminal spines. 



