148 Illiiwis State Lahoratory of Natural Iliatory. 



characters and seems to be a distinct species. Michaelsen 

 states that Gartnaii's paper upon Dlplocardla commuiiis 

 was not accessible to him. If it had been, I can see no 

 sufficient reason why he should not have included the 

 new species in the genus Diplocardia. If I am right in 

 not regarding the presence of a double dorsal vessel and 

 of a fixed number of spermathecse as necessarily of 

 generic importance, and hence in including D. riparia in 

 the same genus with D. communis, then I think the new 

 species ascribed by Michaelsen to the genus Geodrilus 

 really belongs to the genus Diplocardia, since it has all 

 the other characters of that genus, as far as can be de- 

 termined from his quite full description, and has no 

 characters that in my judgment are to be considered 

 generically different. I think, therefore, that the new 

 form should be known as Diplocardia eiseni. 



If Michaelsen be correct in his assumption that Ude's 

 description of Geodrilus singularis was erroneous in cer- 

 tain particulars, and, further, in placing his species in 

 the same genus with that of Ude, then it would seem 

 that G. singidaris must also be regarded as a Diplocar- 

 dia. I do not, however, believe that this point can be 

 actually settled until G. singularis can be more fully de- 

 scribed. 



The following are some of the differences which dis- 

 tinguish D. riparia from D. eiseni : (1) The sperma- 

 thecal pores are in the posterior part of the somite 

 in the latter species, while in the former they are near 

 the anterior margin; (2) the ventral setae of somites 

 YIII and IX are modified in D. eiseni and not in D. 

 riparia; (3) a glandular thickening of the ventral sur- 

 face of somites VIII and IX is present in D. eiseni and 

 not in D. riparia; (4) setae 2, or "b," are present in 

 somite XIX in D. eiseni and not in D. riparia; (5) the 

 first pair of nephridia in D. eiseni is found in somite 

 III, while in D. riparia a pair is present in somite II; and 

 (6) the fiist dorsal pore seen in D. eiseni is in the first 

 clitellar somite, while in D. riparia it occurs in the an- 

 terior part of somite XI. 



