Species of North American Oligoch(£ta. 295 



posterior margin of their somites XI, XII. In all the 

 specimens examined gonads were present in IX — XII. 



No attempt will be made at present to distinguish fully 

 between generic and specific characters. The characters 

 of the setae and of the branches of the dorsal vessel 

 distinguish Thinodrilits inconstans from other Lun^bri- 

 culidse except Lumbriculus, while the number and posi- 

 tion of the various reproductive organs distinguish it 

 from that genus. Its relation to Liinnbri cuius Itmosus 

 Leidj (5, p. 49) cannot be determined until more is 

 known of that species. It seems probable enough that 

 they may belong to the same genus, though I do not 

 think that they are identical if the setae of L. limosus are 

 correctly figured by Leidy (5, PI. 2, Fig. 16), since the 

 distal portion is much more curved in his figure, and the 

 point of abrupt change in diameter is considerably 

 nearer the distal end than in the setae of Thinodrilus 

 inconstans. Also, the number of caecal appendages of the 

 dorsal vessel is greater than I have noticed in the latter 

 species. In spite of these differences, however, there is a 

 possibility that the forms may prove to be identical. 



The genus Diplocardia apparently contains five dis- 

 tinct species, and is distributed over an area extending 

 from Florida at least half way across the continent. 

 Sparganophilus has several species and at least as 

 wide a distribution. Benham (2, p. 175) suggests that 

 the occurrence of S. tamesis in England is due to its 

 importation, presumably from America, which seems 

 highly probable, especially as Moore (9, p. 473) reports 

 the occurrence of that species near Philadelphia. Blmas- 

 tos is very distinct from the European Lumbricidae. In 

 view of the above facts, the distinctness of the Palae- 

 arctic and Nearctic regions as shown by the earthworm 

 fauna would seem greater than has previously been sup- 

 posed. 



I take this opportunity to express my gratitude to 

 Prof. Fl L. Mark, of Harvard University, through whose 



