168 Illinois State Laboratory of Xatmrd Historif. 



Inner ramus of right fifth leg one-segmented, very narrow, 

 extendmg about half its length beyond the end of the first 

 segment of the outer ramus; apex with an acute triangle, 

 hairy at the tip ; sides parallel. 



First basal segment of the left fifth leg produced on the 

 anterior aspect, near the outer margin, into a long tubercle 

 ending in a minute, sharp spine ; second basal segment with 

 delicate hair near the outer distal angle. First segment of 

 the outer ramus subquadrate, shorter than the preceding, 

 slightly longer than broad ; second segment about as long as 

 the first and about twice as long as wide ; very similar to the 

 corresponding segment of D. slcilis Forbes. 



Inner ramus of left fifth leg long and narrow, margins sin- 

 uously curved ; extending about to the middle of the last 

 segment of the outer ramus ; delicately hairy at the tip. 



Second basal segment of fifth leg of female (PI. XXXII. , 

 Fig. 1, 2) with the usual delicate hair at the outer margin. 

 First segment of the outer ramus about twice as long as 

 wide ; second segment somewhat longer than the first, taper- 

 ing to a rather sharp point and curving outward slightly, 

 delicately denticulate on the inner margin; third segment 

 wanting, represented by two spines, the outer about twice as 

 long as the inner. 



Inner ramus one-segmented, extending slightly beyond 

 first segment of the outer ramus, hairy, ending in acute tri- 

 angular tip ; armed at the apex with two rather long sub- 

 equal spines which are sometimes hairy. 



Length of female .97 mm. ; of male .9 mm. 



A reference to the " Distribution of American Species" (see 

 page 183), will show the wide range of this form. In the 

 collections of the U. S. Fish Commission from Lake Samma- 

 mish. Lake Union, and Lake Washington, Wash. ; Tsiltcoos 

 Lake, Tahkenitch Lake, and Klamath Lake, Oregon ; and 

 Lake Pend d' Oreille and Gamble's Lake, Idaho, D. aslilandl 

 was found in immense numbers, being either the only centro- 

 pagid or occurring in connection with Epischura nevadensis 

 Lilljeborg. 



