444 Illinois State Laboratory of Natural History. 



Tubifex rivulorum Lamarck. 



Length 25-50 mm.; number of somites 50-60. Dorsal 

 bundles with three kinds of setae : capilliform setae, four or five 

 per bundle anterior to clitellum, decreasing in number pos- 

 teriorly and absent from the last few somites ; pectinate setae, 

 in somites anterior to the clitellum ; and uncinate setae in 

 other regions. Ventral bundles with four or five uncinate 

 setae in anterior part and fewer posteriorly. In Illinois 

 specimens the ventral bundles sometimes contain pectinate 

 setae. No ventral setae on XL Clitellum on XI and most of 

 XII. Alimentary tract spiral-like in appearance, but with 

 dorsal vessel on the upper side throughout its course. One 

 pair of "hearts" in VIII. First nephridium in VII. Penis 

 with a very short delicate chitinous sheath near tip. 



Limnodrilus claparedianus Ratzel. 



Length 40-70 mm. ; number of somites 145-160. Setae 

 all uncinate ; five to seven per bundle in anterior part, fewer 

 posteriorly. Clitellum on XI and XII. " Hearts " in VIII. 

 Penis with chitinous sheath .5-1 mm. in length, which is 

 twenty to thirty times its diameter. 



Rhizodrilus lacteus n. g. et n. sp. 



The species bearing this name is fairly abundant in Flag 

 Lake, one of the larger bodies of water occurring in the bot- 

 tom-lands of the Illinois River near Havana, 111. Nothing- 

 is known of its distribution in other regions. Specimens have 

 been found in considerable numbers among the roots of sub- 

 merged or partially submerged Sagitta/ria variabilis, but thus 

 far in no other situation. They are sexually mature in July. 



The worm is rather sluggish in habit, and the body is 

 usually contorted and in an almost inextricable tangle. It 

 varies from 70 to 100 mm. in length in sexually mature 

 individuals ; is quite slender, varying from .4 to .6 mm. in 

 diameter; and is largest in the region of the reproductive 

 organs. The body is nearly white, owing to the great number 



