Two New OligochiBta froTn Illinois. 139 



The color is somewhat darker than that of D. communis, 

 which is flesh-colored. The difference is very pronounced 

 on the dorsal surface of the region anterior to the 

 clitellnm, wbere the surface becomes dark brown, this 

 color being usually retained in alcoholic specimens. Pos- 

 terior to the clitellnm the brown dorsal vessel and its 

 lateral branches are very conspicuous through the body 

 wall of the living animal. 



The clitellum is of a dull copper-color, and extends 

 over somites XIII to XYIII, inclusive. As in D. com- 

 munis, it is absent or but slightly developed upon a 

 narrow median ventral area of those somites. The setae 

 have the same arrangement and distribution as in D. com- 

 irrnnis. The first dorsal pore is near the groove between 

 X and XI. The number and position of the gizzards, in 

 somites V and VI, the character of the typhlosole, and 

 other main features of the alimentary tract, are the same 

 in the two species. The nephridiopores are in the vicinity 

 of the outermost setce. 



The generative systems of the two species are alike in 

 main chaiacters, but present specific differences. Two 

 pairs of ciliated rosettes are present in each of the species, 

 occupying the usual position in somites X and XI. 



An anomalous position for the testes was ascribed by 

 Garman to D. communis. After having sectioned speci- 

 mens of that syjecies, I find that some of the reproductive 

 organs were misinterpreted by him. Two pairs of digi- 

 tate testes are present in each of the species. These 

 have the usual position, being attached to the anterior 

 septum of each of somites X and XI. 



In number and position of sperm-sacs the two species 

 agree. There is a pair of pre-septal lobulated sperm- 

 sacs in somite IX, and a pair of post-septal lobulated 

 sperm-sacs in somite XII. The latter, in D. communis., 

 were described b^'^ Garman as testes. 



Somites X and XI ai-e filled with developing sperma- 

 tozoa during the reproductive season, though no definite 

 sacs have been observed. The situation of the sperm- 

 duct in D. riparia is like that in D. communis. The 



