36 Illinois State Laboratory of Natural History. 



localities this proportion . only varied l)y one thirtieth. The 

 inner margins of the stylets are ciliate. The lateral spine is 

 a tritle hehind the middle ; the outer seta about as long as 

 the ramus; the inner five sixths the length of the third from 

 within ; the latter two thirds as long as the second. 



The antennae terminate between the end of the second and 

 the end of the third segments. There is a sense-club and 

 seta on the twelfth segment. The sixteenth segment is never 

 longer than the seventeenth. The sixteenth and seventeenth 

 segments bear hyaline plates (PI. IX., Fig. 2), that of the six- 

 teenth segment being very narrow, with its edge entire, and 

 that of the seventeenth broader, with its edge deeply notched. 

 The notches are most pronounced near the distal end and fade 

 away in each direction. Tlie intervening teeth point str<mgly 

 toward the base of the antenna. The segment is excavate on 

 the inner side, and the hyaline lamella completes the normal 

 outline of the segment by hlling up the depression. 



The swimming feet are armed as follows : — First pair : outer 

 ramus, two spines, four set:e ; inner ramus, one seta, one 

 spine, four sette. Second and third pairs : outer ramus, three 

 spines, three sette ; inner ramus, one seta, one spine, four 

 set*. Fourth pair: outer ramus, three spines, four sette ; 

 inner ramus, one seta, two spines, two setct. 



The feet of the fifth pair (PI. IX., Fig. 3 ) are two-segmented. 

 The distal segment bears two parallel seta% the outer one of 

 which is set at about the middle of the segment. This seta is 

 most strongly spinulose on the outer side, while the distal one 

 is plumose on both sides. 



The rcc('j)f((ciiliiui scuiinis is large and elliptical, the long- 

 axis corresponding to the long axis of the segment. The 

 lateral canals are connected with the expanded upper portion. 

 The receptaculum is almost exactly as in ('. Ifiicl,<ti-ti. 



The egg-sacs are elliptical and stand out from the abdomen. 



The usual length of the female is 1.2-1.4 mm. 



