554 



"hearts" in XTl. Dorsal vessel siii.i^le. Alimentary tract very narrow 

 in XVI and abruptly enlarged in XVll. SpermatheCcC in \'II, VIII, 

 and IX. Sperm sacs in IX and XII. 



Among the earthworms collected in 1895 at Havana, were many 

 specimens of this small type of Diplocardia which in anatomical char- 

 acters corresponds very closely with the revised description of P. 

 singidaris (Ude) — see Ude ('95: 129). In a former paper by the 

 writer ('95b 1285), these worms were treated as belonging to tide's 

 species, and in a later paper ('00:442) they were listed as D. sin- 

 gidaris, which species was mentioned as of frequent occurrence at 

 Havana and Urbana. The specimens found at Urbana are without 

 pigment and are of considerably stouter proportions than the Havana 

 specimens. They occur in upland wooded situations as well as in tree- 

 less areas. I think that the Urbana specimens are without doubt rep- 

 resentative of Ude's D. singidaris, the type specimens of which were 

 collected at Danville, Illinois, only thirty miles east of Urbana. The 

 Havana specimens are very heavily pigmented anteriorly and quite 

 slender. They are very abundant in the muddy banks of Spoon River 

 near its entrance into the Illinois River, and are so situated that they 

 are submerged for weeks at a time during high water when the bot- 

 tom-lands are flooded. 



The recognition of the Havana specimens as belonging to a dis- 

 tinct variety, as named and described above, will simplify subsequent 

 treatment of still other material which is closely related to D. sin- 

 qidaris and D. couuintnis Garman. Despite the fact that some leading 

 investigators of the Oligochccta do not consider the last-named forms 

 as constituting distinct species, it seems to the writer that D. sin- 

 gidaris, with its single dorsal vessel and its clitellum nearly as thick 

 ventrally as dorsally, must be given rank as a species distinct from 

 D. conunuins with its double dorsal vessel and saddle-shaped clitellum. 



EXPI^ANATIONS WITH REC.\RD TO KEY 



.A.S the following key may often 1)e utilized l)y persons not famil- 

 iar with tlie various symbols and terms in common use in systematic 

 papers dealing with earthworms, it seems desirable that some of these 

 be explained. 



Roman numerals are generally used to designate the number of 

 a somite, counting from the anterior end. When the separation be- 

 tween somites is obscure, advantage mav be taken of the fact that in 

 the species found in Illinois the first setai are always borne on the 

 second somite. Externally the limits of somites are ordinarily in- 

 dicated by transverse (intersegmental) grooves, while internally the 



